5>r^’l6 FEDERAL DEMOCRATIC REPUBLIC OF ETHIOPIA MINISTRY OF WATER RESOURCES ERER DAM & IRRIGATION DEVELOPMENT PROJECT Final Detail Design Report Annex E: Irrigation & Drainage Design May, 2009 CONFER T ENGINEERING AND CONSUL TING ENTERPRISE P.L.C. (CECE) ENGINEERS WATER RESOURCES A AGRICULTURAL DEI 'ELOPMENT PLANNERS p.o.nox bow fEL. 251-11 -6639244 FAX 2*1-11-64J9245Executive Summary Volume I: Dam & Appurtenant Structure Annex A: Dam Design Annex B: Dam Appurtenant Structures Annex C: Geotechnical Study Annex D: Hydrology Volume II: Irrigation & Drainage Annex E: Irrigation & Drainage Design Annex F: Road Infrastructure Annex G: Project Control Centers Annex H: Operation & Maintenance Manual Volume III: Project Worth AnalysisTable of Contents 1.0 Introduction................................................................................................................................... 1 1.1 Aim of Project.............................................................................................................................................. 1 1.2 Location of Project.......................................................................................................................................1 1.3 Access to the Project Area........................................................................................................................... 3 2. About the Project............................................................................................................................. 4 2.1 Source of Irrigation Water........................................................................................................................... 4 2.2 Climatic Conditions..................................................................................................................................... 5 2.3 Topography of Command Area................................................................................................................... 6 2.4 Population.....................................................................................................................................................6 2.5 Land Use...................................................................................................................................................... 7 2.6 Project Components.................................................................................................................................. 7 3.0 Soil Suitability................................................................................................................................ 8 3.1 Physical Characteristics............................................................................................................................... 8 3.1.1 Texture.................................................................................................................................................8 3.1.2 Drainage Class.....................................................................................................................................8 3.1.3 Soil Depth............................................................................................................................................8 3.1.4 Soil Type............................................................................................................................................. 9 3.1.5 Infiltration Rates..................................................................................................................................9 3.2 Chemical Characteristics............................................................................................................................10 4.0 Crop Water Requirement........................................................................................................... 11 4.1 Cropping Pattern........................................................................................................................................11 4.2 Proposed Cropping Pattern........................................................................................................................11 4 3 Crop Water Requirement............................................................................................................................12 4.4 Irrigation Scheduling................................................................................................................................... 13 5.0 Irrigation Water Quality............................................................................................................ 15 6.0 Field Irrigation.............................................................................................................................16 6.1 Depth of Watering......................................................................................................................................16 6.2 Field Irrigation Efficiency..........................................................................................................................17 6.3 Field Channel Discharge............................................................................................................................ 17 6.4 Field Size.................................................................................................................................................. 18 6.5 Furrow Spacing..........................................................................................................................................18 7.0 Irrigation System......................................................................................................................... 19 7.1 Canal System............................................................................................................................................. 19 7.1.1 Primary Canal................................................................................................................................... 19 7.1.2 Secondary Canals............................................................................................................................. 19 7.1.3 Tertiary Canals..................................................................................................................................20 7.1.4 Quaternary Canals............................................................................................................................ 20 7.2 GCA AND CCA....................................................................................................................................... 21 7.3 Irrigation Intensity..................................................................................................................................... 22 7.4 Night Irrigation...................................................................................................................................... 237.5 Irrigation Efficiencies.............................................................................................................................. 24 7.5.1 Storage Efficiency..........................................................................................................................25 7.5.2 Conveyance Efficiency.................................................................................................................. 25 7.5.3 Field Application Efficiency..........................................................................................................25 8.0 Planning and Design of Canal Network................................................................................. 26 8.1 Canal Alignment............................................................................................................................ 26 8 2 Canal Design...........................................................................................................................................27 8.3 Design Criteria............................................................................................................................... 28 8.3.1 Limiting Velocities....................................................................................................................... 29 8.3.2 Working Head............................................................................................................................... 29 8 3.3 Longitudinal Slope........................................................................................................................ 29 8.3.4 Critical Velocity Ratio (CVR)...................................................................................................... 30 8.3 5 Free Board............................................................................................................................ 31 8.3.6 Bank Width.................................................................................................................................. 31 8.3.7 Saturation Gradient...................................................................................................................... 31 8.3.8 Inspection Roads.......................................................................................................................... 32 8.3.9 Canal Embankment Material........................................................................................................32 8.3 10BERM................................................................................................................................. 33 8.3 11 CatchWater Drain...............................................................................................................33 8.4 Command Area And Design Discharges For Quaternary Canals........................................................ 34 8.5 Calculations of Design Capacities........................................................................................................36 8.5.1 Quaternary Canals....................................................................................................................... 36 8.5.2 Tertiary Canals............................................................................................................................ 37 8.5.3 Secondary Canals........................................................................................................................ 37 8 5.4 Primary Canal............................................................................................................................. 3S 8.5.5 Capacity Statements for Different Reaches........................................................................... 39 8.6 Procedure Adopted for Design............................................................................................................ 44 9.0 Irrigation Structures............................................................................................................. 45 9.1 ESCAPE Structures.....................................................................................................................45 9 1.1 Choice of Types of Escape......................................................................................................... 45 9.1.2 Criteria for Location................................................................................................................... 46 9.1.3 Criteria for Escapes Capacity..................................................................................................... 47 9.1.4 Design Considerations............................................................................................................... 48 9 2 Canal Head and Cross Regulators.......................................................................................................49 9.3 Outlet Structures:................................................................................................................................50 9.4 Drop Structures.................................................................................................................................. 53 9 5 Tertiary canal Head Regulator........................................................................................................... 54 9 6 Duck Bill Weir Structure....................................................................................................................55 9.7 Tail Escape Structures........................................................................................................................ 55 10.0 Cross Drainage Structures................................................................................................56 10.1 Aqueducts........................................................................................................................................56 10.2 Culverts.......................................................................................................................................... 60 11.0 Field Drainage System...................................................................................................... 63 111 Excess Rain Water........................................................................................................................... 6511.2 Excess Irrigation Water.......................................................................................................................67 11.3 Field Drain Capacity.......................................................................................................................... 67 11.4 Tertiary Drains.................................................................................................................................... 68 11.5 Drain Layout....................................................................................................................................... 69 12.0 Flood Protection Embankments........................................................................................... 71 12.1 Design Criteria................................................................................................................................... 71 12.2 Design of Embankments.................................................................................................................... 73 13.0 Construction Materials.........................................................................................................75 13.1 Earthworks......................................................................................................................................... 75 13.2 Masonry and Concrete Works........................................................................................................... 75 14.0 Operation and Maintenance of Irrigation System............................................................. 76 14.1 Dam Structure...................................................................................................................................76 14.2 Regulatory Structures....................................................................................................................... 76 14.3 Operation Of Reservoir And Conyeyance System :......................................................................... 77 14.4 Field Irrigation.................................................................................................................................. 78 14.5 Maintenance...................................................................................................................................... 78 14.5.1 Canal Network....................................................................................................78 14.5.2 Field System........................................................................................................ 78 14.5.3 Drains.................................................................................................................. 78 14.5.4 Roads................................................................................................................... 78 15. Land Grading....................................................................................................................... 79Erer Dam & Irrigation Project /CECE & CES 1.0 Introduction 1.1 Genesis of the project Ethiopia is confronted with food scarcity problem. Rain fed agriculture is being practised with age old agricultural technology which has resulted in low production. Irrigated agriculture is recognised as one of the major means to solve the food deficit problem and alleviate the poverty of rural people, besides ensuring increased production of raw materials for agro-industry, reduced food import, savings in foreign exchange and creating employment opportunities. Considering the importance of irrigated agriculture in all round development, the government of Ethiopia had initiated action to bring more and more area under irrigated agriculture In 1998, Wabe Shebelle River Integrated Master Plan was drawn up and Erer irrigation project was identified as one of the potential scheme for development of irrigated agriculture. Consequently Pre- Feasibility and Feasibility studies were carried out by Water Works Design and Supervision Enterprise ( WWDSE ) in association with WAPCOS and Synergies India Pvt,Ltd. respectively in 2002-05 and 2006-07. This project was found technically feasible, economically viable, environmentally sound and socially equitable and therefore recommended for implementation The detailed designs are now being prepared to enable the government to implement the project with promptitude. Table 1.1 Salient Features of The Project Description Figures Latitude and Longitude (Command area) UTM 1009300 N to 1028300 N (9°0717" N to 9°17 40" N) and UTM 193375 E to 199650 E (42°12 24 E to 42°1603 E) Catchment area 419.00 Sq. Km Annual rainfall 650 mm to 800 mm Net CCA 3722 Ha River Bed (deepest) • 1348.00 m Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES Dead Storage Level / New Zero Elevation (50 years) • 1369.85 m MDDL 1371.00 M FRL 1379 00M MWL 1382.60 M Dam Type Zoned Earth fill Top of Dam 1384.60 m Maximum height of dam 36.60 m Gross storage 5067 50 Ha-m Live storage 2303.40 Ha-m Spillway Type Ogee weir with inclined chute Waterway of spillway 30 m Inflow design flood (greater of 0.5 PMF and 10,000 year return period) 641.90 Cumec Spillway routed flood 440.50 Cumec Area to be irrigated (CEA) 3370hectarcs FIRR 11 16(%) E/RR 14.56 (%) B/C ratio 1.50 NPV (financial) 204* 106 birr NPU (economical) 122*106bin Financial & economic viability verified L------------------------------—---------------------------------------- i 1.2 Location of Project The Erer Irrigation Project proposes to draw irrigation supplies from Erer River which is a tributary of Wabe Shebelle River. The project is located at about 530 km from Addis Ababa and 19 km from Harar town. The command area is situated on both sides of Harar-Jijiga road which is 2 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES 11 km from Babile town towards Harar. The proposed dam site is situated about 6 km on left side of Harar-Jijiga road (see figure 1.1). Erer Irrigation Project is located in two Regional States, namely Regional State of Harari and Regional State of Oromia. In Oromia, project area is situated in Babile of the East Hararge Zone In Harari it is situated in Erer and Soft Woredas. The command area is situated in 2 Kebeles (Kile and Erer Dodota) of the Harari Region and in about 7 Kebeles ( Erer Ibada, Ifadin, Gamachu, Erer Guda, Tula, Berkele and Tofiq ) of Oromia region. Major part of command lies in Erer Ibada and Efadin Kebeles. The command area starts from some distance downstream of the dam and extends only on right bank of Erer river The command area is narrower and smaller near the dam site and becomes wider in the downstream side. The irrigable area is mainly situated below the bridge on Harar Jijiga road and extends beyond confluence of Erer River and Bidisimo stream covering only the right bank of the river. Although suitable areas are available on left side of the river also, due to limitation of water availability for irrigation only the command on the right bank of Erer River is chosen for this project. The command area is located between UTM 1009300 N to 1028300 N ( 9° 07’ 17” to 9° 17’ 40”Latitude ) and UTM 193375 E to 199650 E (42°12’24”to 42° 16’ 03’’Longitude). 1.3 Access to the Project Area The project area can be accessed by an asphalt road (511 km) from Addis Ababa to Harar town and further 19 km by all weather gravel road which connects Harar with Jijiga town. Harar town can also be accessed partly by air up to Dire Dawa and remaining about54 km. by road from Dire Dawa to Harar.Babile is the nearest town which is 11 km from project area. The proposed dam site which is about 6 km from Harar- Jijiga road, is connected by fair weather road. The entire proposed command area from head to tail is connected by fair weather road and therefore, the area can be accessed for carrying construction materials and equipment without making special arrangement of approach roads , 3 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009DAM AXIS. .DAMJCC LEGEND PRIMARY CANAI. SECONDARY CANAL ROAD INDEX CONTOUR INTERVAL CONTOUR DENCH MARK RIVER NATURAL DRAIN UN SUTTADU! (AND IRRIGATION Pt£. FEDERAL DEMOCRATIC REPUBLIC OF ETHIOPIA MINISTRY OF WATER RESOURCES XT's CONCERT ENGINEERING AND CONSULTING ENTERPRISE ----- --------- IN ASSOCIATION WITH CONSULTING ENGINEERING SERVICE ( INDIA ) PVT. LTD *1 r J PROJECT}- ERER IRRIGATION PROJECT DETAIL DESIGN TITLE*- SERVICE ROAD NETWORK mmmmm mil m m i ximviini* DYi hath MrIW» IM<A»'N DY. TOMAS U KAI II iav»» ihsiiih IlYMHAILI! hkvwinNn IMTAII. ANRUVIJ) DV.A MEMRS1H l«AW>MI|Ml N.E1M1IIErer Dam &. Irrigation Project ZCECE & CES t 2, About the Project 2,1 Source of Irrigation Water The source of irrigation water for the proposed command area is the flows of Erer River Error is n tributary of Wabe Shebelle River which is situated in the semi arid area of Wabe Shebelle basin Wabe Shebelle river basin is located between 0°N to 9° 30’ latitude and 38° 30' E to 46° E longitude , Il originates from the Bale mountains at an approximate elevation of 4000 m above mean sea level and drains in to Indian Ocean, after crossing Somalia, The total basin of Wabe Shabelle is approximately 280,000 km2, of which 72 % Iles In Ethiopia. Large part al’ Somalia, pari of Oromia, part of Southern Nations, Nationalities and People (SNNP), pail of Dire Dawn and the entire llarari, are located in Wabe Shebelle Basin Erer River and Ils tributaries originate from the highlands close to kombolcha town where general elevation Is about 2500 in above mean sea level 'flic Erer catchment up to the proposed dam site la about 419 km2 The water shed has dense network of tributaries The major tributaries are sainte, Clttdl, Ulan-ula, kombolcha, Boscnsa, Hida and Daka The topography of the catchment la dominantly mountainous and hilly with relatively flat and rolling land along Brer River Owing to intensive deforestation, cultivation and overgrazing (he land degradation Is serious problem in the Erer River catchment Thu catchment area of Erer River at bridge on Harar • -Jljiga road is 469 km2 where discharge data arc available for shoitci length of time. The discharge of Error is mainly dependent on rainfall which is highly variable in time and space. The water demand for Irrigation does not match with the water availability in the river, therefore storage darn is proposed to Htoru the llood discharge and utilise in the times for irrigation and other uses 4 Annex E : Irrigation <St Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES 2.2 Climatic Conditions The Erer valley command area is situated in sub-tropical climate having mean annual temperature 22°C,altitude between 1280 to 1365 meter above mean sea level, annual mean evaporation of 1658 mm and mean annual rainfall 650mm ( effective rain fall 292 mm). Table 1 Climatological Parameters of Command Area Data Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Rainfall (mm) 13.4 20.6 54.1 1154 92.2 59.4 88.5 100.7 85.8 39.7 16.4 7.1 75% Dep. rainfall (mm) 0 0 10.2 486 46.2 22.9 48.1 60.6 44.3 11.0 0 0 Max temperature (oC) 22.2 23.0 24.2 24.0 23.1 22.4 22.8 23.3 23.7 22.5 22.2 21 8 Min temperature (oC) 17.5 19.2 20.0 18.9 19.5 19.1 19.2 19.4 18.6 19.4 16.0 17.2 Wind speed (m/sec) 1.61 1.62 1.30 1.09 0.95 0.94 0.95 0.94 095 0.99 1.36 1.55 Sunshine hours (hrs) 88 8.3 7.9 7.5 8.5 8.1 7.5 7.8 7.6 8.4 9.3 9.2 Relative Humidity (%) 52.6 52.7 54.0 56.1 50.9 45.7 51.3 54.4 54.1 45.6 46.1 51.2 A summery of important climatic parameters relevant to planning of irrigated agriculture representing the command area indicate that the rainfall in the command area has bimodal pattern, first peak in April -May and second in August-September. The rain fall during the months of June and July is low and uncertain In remaining months there are no rains. This shows that crop growth season has to coincide with the rainy months This is responsible for poor productivity. Length of growing periods and sowing times of crops depend mainly on minimum and maximum temperatures which vary within a narrow limit. This permits the sowing and harvesting of crops at convenience depending upon availability of water. 5 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES The remaining parameters such as wind speed and relative humidity have only moderate values and do not affect crop productivity and crop water use significantly. The sun shine hours indicate long bright days having eight to nine and half hours of bright sun shine During the rainy season the sunshine hours get reduced to six to seven hours owing to clouds. The climatic parameters indicated above suggest that crop production cannot be increased and stabilised without assured irrigation in the proposed command area of Erer project 2.3 Topography of Command Area. The topography of proposed command area varies from flat to gently slopping. The altitude of command area varies from 1280 to 1365 m above mean sea level The surrounding cultivated areas of Harar and Babile Woreda are situated on higher elevation. No major effort would be required for levelling of land if irrigated agriculture is to be practised. Also, natural vegetation is sparsely located and shallow rooted excepting some patches where acacia trees exist. Only moderate expenditure will be involved in removing the natural vegetation and preparation of land for irrigation 2.4 Population The total population of the rural communities of two regions is 40,317 who are clustered in about 7,934 households Eleven Kebeles fall in command and reservoir areas. It is estimated that about 3,462 households will need to be displaced from their villages and/or lands from reservoir area (approximately 1985 ha) These households need to be settled at other places. The quality of housing in project affected area is good The majority of people live in wood and mud houses with corrugated iron sheet roofs. The majority of houses tend to give shelter to both people and their livestock. The coverage of potable water is limited to about 48 % households (feasibility study, volume, sectoral report 13. 6 Annex E Irrigation & Drainage Design /Final Detail Design Report /2009Ercr Dam & Irrigation Project ZCECE & CES 2.5 Land Use The designated area of Erer irrigation project is surrounded by extensive coverage of natural vegetation comprising of cactus, thorny bushes, shrubs and acacia trees with very little grazing land which is located beneath the natural vegetation and on steep sloping lands. As observed, the cultivation is mainly rain fed in majority of areas situated in the proposed command area of the project excepting in riverbed where some irrigated agriculture is being practised There are three small irrigation schemes already operative in the command area. These are said to have been constructed and operated by Munchen fur Munchen, a NGO The total irrigated area from these schemes is of the order of 20 ha The agriculture practices are traditional oxen-cultivation based and local ploughs and hand tools are used in cultivation. Amongst the crops, most commonly cultivated crops observed are maize, groundnut, vegetable crops (of onion, tomato, pepper) and fruit trees of mango. To some extent sorghum, sweet potato, haricot beans, banana, papaya and citrus are grown in and around command area Chat, a stimulant is also grown extensively The local crop varieties are used. No fertilizers and insecticide/pesticides are being used in rain fed agriculture 2.6 Project Components The Erer Irrigation project is proposed to comprise of the following components- i) A storage reservoir on river Erer situated at about 6.0 km distance upstream of its crossing with Harar-Jijiga road which intends to controls the flow of river water to provide supplementary irrigation water to the area situated in the downstream side of the proposed dam site. ii) A network of canal and drains working in complementary and supplementary manner by serving the irrigation supply and removing the excess water in appropriate time from irrigated command 7 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES 3.0 Soil Suitability Soils influence crop suitability, choice of land utilization types, drainability etc. Therefore extensive soil surveys and investigations are carried out in fairly large area encompassing the whole of the proposed command of Erer irrigation project. The soil surveys and investigations have provided detailed information on the soils and land of command area for selection of crops and irrigation designs. 3.1 Physical Characteristics 3.1.1 Texture Mosty the soil is of has clay loam and loam texture. The soils derived from volcanic ash and limestone has loam or silty clay loam texture. The soils derived from sandstone fall under the sandy textural class. 3.1.2 Drainage Class The concept of soil drainage refers to the frequency and duration of periods when soil is free of saturation or partial saturation by water The soil drainage is reflected by colours of soil materials. The soil drainage of the project area falls in moderate drainage class The soils situated in flood plains are imperfectly drained because they are situated in low areas 3.1.3 Soil Depth The soils in proposed command area are deep to very deep, except the dissected to undulating dissected and rolling dissected soils, which are shallow to very shallow soils. Thus depth of soils will not cause any problem for irrigated agriculture. 8 Annex E . Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES 3.1.4 Soil Type Medium texture soils are found to be situated in higher elevation areas which are either luvisols or cambisols These are easy to manage and have good permeability and productivity The soils mainly along riverbed are vertisols which are black to dark brown in colour. These soils have low permeability and are expanding and cracking type. These soils require special management and attention for adequate drainage. 3.1.5 Infiltration Rates The permeability tests have been carried out along the alignment of primary canal and secondary canals at only four places because on visual examination the soils along the entire alignment of primary canal and secondary canal were found almost identical It was also revealed in pre feasibility and feasibility reports that the soils along the proposed canal alignment were of the same type and were not having high infiltration rates. Therefore no lining was proposed in the feasibility report. In view of this only a few infiltration tests are proposed. The observed rates of permeability and infiltration are given as below: Table 2 Results of Infiltration and Permeability tests Site Location Av. Infiltration rate ( cm/hr) Av. Permeability (cm/s) 1 N:1025471, E:0196270 5.48 2.08* IO-6 2 N: 1020752, E: 0177012 15.02 1.04* IO* 3 N:1012146, E:ol96380 1.96 1.62*10* 4 N: 1016979, E:0193575 2 13 2.08*10* 9 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES If test results at either of the sites had indicated higher infiltration rates more sites would have been selected to identify selected reaches for provide lining. The above table reveals that the infiltration rates are in medium range and do not warrant the provision of the lining in any part of canal system 3.2 Chemical Characteristics On chemical analysis of the soil samples following parameters are obtained: (i) pH ranges ffom6.7 to 8.89 which shows neutral to alkaline At this level availability of micronutrients will reduce (ii) Nitrogen percentage ranges from 0.02 to 0.44 Which is considered low to medium. (iii) Organic Carbon Content varies from 0.479 to 2 99 which is quite low. (iv) Carbon: Nitrogen Ratio ranges from 7 94 to 10 56 which shows that there will be general response to the Nitrogen fertilizers (v) Cation Exchange Capacity varies from 18.81 to 31.93 which is medium to high. (vi) Base Saturation Percentage is greater than 74 22% which shows that the soils are fertile. (vii) Exchangeable Sodium Percentage varies from 1.98 to 6.3 % which is low to medium and are within acceptable limits. (viii) Electrical Conductivity varies from 0.12 to 0.45 dSm’1 which indicates low concentration of soluble salts. The salinity can not be a problem in this type of soils. (ix) The soils have low to medium levels of phosphorus ranging from 4.82 to 18.23 ppm For crops which demand more phosphorus need in excess of 20 %. Thus in general response to the phosphorus fertilizers is expected to be good. 10 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES 4.0 Crop Water Requirement 4.1 Cropping Pattern Climate, soils, availability of water and requirement of food, fibre, money etc. decides the nature, scope and extent of crops to be grown in a particular area. Basically people settled in any area decide the type of crops required to be grown for their own consumption. The main crops to be grown in the command area should be determined in due consultation with the Agriculture Department and the agriculturists, looking to the crops being grown presently and cropping pattern to be introduced for irrigated farming. Crop Calendar, crop water requirement and cropping intensities should be finalized in consideration with socio-economic factors of the area and also on the basis of the experience gained in irrigation projects implemented in the country. 4.2 Proposed Cropping Pattern On interaction with farmers of project area and on the basis of preliminary surveys, referring to the studies done in past, the Project Agronomist has proposed the following Cropping Pattern for Erer Irrigation Project. Table 3 Cropping Pattern Proposed for Erer Project Season 1 Meher Crop type Planting date Area% Maize July 30 Sorghum July 5 Ground nut July 20 Rice July 10 Haricot Bean July 5 Vegetables July 10 Annex E Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES Alfalfa July 5 Sugarcane July 10 Orchard July 5 Total 100% Season 2 Belg Maize Feb 30 Tomato Feb 5 Rice Feb 12 Potato Feb 5 Okra Feb 5 Sweet potato Feb 5 Vegetables Feb 5 Haricot beans April 3 Sugarcane July 10 Alfalfa July 5 Orchard July 5 Total 90 Total Cropping intensity For Season-1 and Season-2 170% ( 20 % crops are perennial crops) 4.3 Crop Water Requirement Crop water requirement is computed on the basis of well known water balance equation as given below: ETo i.e is worked out by using universally accepted Penman-Monthieth equation. CROWAT 4 3 software which is developed most recently is used to work out crop water requirement. WR= (ETo* Kc ( C,T,F )—ER (R,ET,S ) + Ti ) / E Where: 12 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES WR -Gross water requirement ETo -Reference crop evapotranspiration (computed by Penman-Mothieth equation ) Kc - Crop coefficient- a function of C,T,F C - Crop type T - Stage of crop development F - Frequency of soil wetting in the first crop development stage only ER - Effective rainfall (which has been assumed as 80 %) R - Rainfall ET - Actual evapotranspiration S - Soil moisture storage factor Ti - Technical irrigation( Application Loss ) E - Irrigation efficiency The nearest climatological stations close to Erer irrigation project area are Harar Dire Dawa, Bisidimo and Jijiga The climatic parameters viz. mean monthly rainfall, temperature, sunshine hours, wind velocity and relative humidity as recorded at these stations are utilised in working out project climatological parameters after making suitable adjustments for difference in altitude etc 4.4 Irrigation Scheduling • Irrigation schedule is designed to start irrigation from the first planting date of the crops when all of the readily available soil moisture has been used. The irrigation amount will be equal to soil moisture deficit. The soil moisture deficit will return to zero after the irrigation. • The water application time is planned when all (100%) of the readily available moisture has been used up. In this situation the crop will not become moisture stressed. • The water application depth is calculated to refill the soil moisture storage so that the soil may return to its field capacity. (100% of the readily available moisture is replenished). 13 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES • Monthly ETo and monthly rain fall arc distributed using polynomial curve fitting To generate rainfall events, each 5 days of distributed rainfall is accumulated as one storm. • For total and readily available soil moisture the calculation procedure is indicated below. TAM = Total Available Moisture = (FC% - WP %)♦ Root Depth [mm], RAM = Readily Available Moisture = TAM * P [mm] Where: FC = Field Capacity WP = Wilting Point P = Depletion Percentage 14 r- Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Ercr Dam & Irrigation Project /CECE & CES 5.0 Irrigation Water Quality Water samples form Erer River were collected and analyzed at the Water Works Design and Supervision Enterprise (WWWDE) laboratory at Addis Ababa for their physical and chemical properties. These tests were conducted to find out the turbidity, total solids, dissolved solids, electrical conductivity, PH, ammonia, sodium, potassium, magnesium, manganese, fluoride, chloride, bicarbonate, sulphates, phosphates etc. The test results are given in table 2 attached with the feasibility report of irrigation and drainage part. The suitability of water for irrigation has been analyzed in this report and it is confirmed that the Erer river water is suitable for irrigation and is not likely to cause any adverse effect on plants or sails if applied for a long time. 15 Annex E : Irrigation & Drainage Design /Final Detail Design Report 72009Erer Dam & Irrigation Project ZCECE & CES 6.0 Field Irrigation 6.1 Depth of Watering The plant uses the soil moisture available between field capacity (at 0.1 or 0.33 bar pressure) and permanent wilting point (at 15 bar pressure) which commonly called as Available Water holding Capacity usually denoted by AWC. In practice the soil moisture is not allowed to go up to permanent wilting point and next water is applied when available soil moisture is depleted by about 75% or so. This is known as Readily Available Water holding Capacity( TRAWC ) However some agronomists use a rule of thumb and assume two third of the total available moisture between field capacity and permanent wilting point as available soil moisture for plant In case of Erer project this figure is taken as 70% On studies of soils in command area following AWC values were found (refer Pre- Feasibility Report) Table 4 AWC Values for different soils of Command Area Profile No. FAO Soil Units AWC mm/m TRAWC mm/m (E)DP3 Vertic Luvisols 143 100 (E)DP5 Eutric Camb iso Is 142 85 (E)DP8 Eutric Vertisols 159 111 (E)DP9 Vertic Cambisols 165 99 (E)SP1 Chromic Luvisols 155 93 (E)SP3 Vertic Luvisols 179 107 (E)SP5 Eutric Vertisols 152 106 Average 100 Average Readily Available Water Holding Capacity=100 mm The peak evapo-transpiration are given as under( Refer Sectoral Report on Agronomy): 16 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES Table 5 Peak evapo-transpiration rates for different crops Crop Peak Daily ETc (mm) Sorghum 4.7 Maize -I 4.9 Rice 5.1 Ground nut 4.4 Vegetables 2.6 Alfalfa 4.7 Sugarcane 4.7 Maize-II 4.7 Since Rice is not a dominant crop hence it is ignored for fixing the irrigation intervals. Daily ETc for most of the crops vary between 4.4 and 4 9 For calculation of irrigation intervals the maximum ETc of Maize-I is used. Maximum interval at peak irrigation requirement shall be 100.0/4.9 = 20.40 say 20 days. The root depth of maize is 1.0 m. 6.2 Field Irrigation Efficiency Field irrigation efficiency of 70% can be achieved and hence the same is assumed for ascertaining the feasibility of this project 6.3 Field Channel Discharge The field channel discharge must be limited 80 lit/sec ( average about 60 lt/s ), which can be conveniently managed by the individual farmer. Under no situation it may be allowed to exceed 80 lt/s. Therefore, it is recommended that the design capacity of the field channels may be adopted 17 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES equal to or less than 80 lit/sec. preferably 60.0 It/s. Normally a discharge of 20It/s is considered as minimum flow rate to irrigate a field 6.4 Field Size The field size can be determined as below:- Unit watering depth =90 0mm Field efficiency =70% Gross unit watering depth = 128.6mm(90/ 0.7) Irrigation interval =20 days Field channel discharge(max) =60 lit/sec Field size (ha) max 4 =(60*20*24*3600)/( 1000*0 1286* IO ) = 80 5 Say 80ha 80 ha max field size is adopted for the design of quaternary canal This is the size of command of quaternary canal carrying discharge of 60 It/s. The field is divided into 3 to 5 sub fields depending upon topography. Each sub field of 20 to 40 ha will be served by a field channel taking water from quaternary canal. A small masonry structure termed as turn-out is provided as per requirement for delivery of water in to field channels at suitable places 6.5 Furrow Spacing Considering loamy soils and 0.1- 0.2% slope of land the furrow length of 250m is adopted. Most of the crops are sown on furrows having 0.9m spacing. The same spacing is adopted in this project 18 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES * 7.0 Irrigation System 7.1 Canal System 7.1.1 Primary Canal Canal system comprises of primary canal which off takes from Irrigation Outlet located on the right bank of river downstream of dam structure. The layout of the primary canal is guided by minimum drawdown level in the reservoir and topography of the command area. The full supply level (FSL) of the primary canal is fixed in such a way that it is able to provide flow irrigation under gravity to its entire command. In design of the dam sufficient working head has been provided between proposed FSL of the primary canal and maximum drawdown level in the reservoir. The full supply level of the primary canal at its head is kept at EL. 1365.0 m above msl. The primary canal is aligned as a contour canal providing sufficient slope ensuring adequate velocity. As per nomenclature followed in Ethiopia the primary canal is termed as “P”. Tertiary canals off taking from primary canal are designated as Tl-P, T2-P etc. The quaternary canals off taking from primary canal are designated as Ql-P, Q2-P and so on 7.1.2 Secondary Canals Two secondary canals off take from primary canal at change km 14.67 and are designated as SI and S2. Both these canals have head regulators which act as cross regulators for other secondary canal. First secondary canal (SI) travels across the contour and negotiates a fall of 40.0m through small vertical falls of 0.5m drop. The depth of drop is taken as 0.5m according to economy _______________________________________________________________________ 19 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES__________________________________________ • • considerations. After reaching a level of ELI 320.0m the canal is planned as a contour canal to irrigate an area situated on its left side at a level lower than FSL. r* Second secondary canal (S2) off takes from the tail of primary canal and passes through the rugged mountains comprising of ridges and valleys. The canal is planned as a contour canal on the hill slopes and has a very tortuous alignment till it crosses river Dencho. The alignment of this canal, as proposed in feasibility report is not considered appropriate around the site it crosses Dencho river because the required height of aqueduct will be very high. Therefore the alignment is amended considerably around its crossing with Dencho river and the height of aqueduct has been reduced 7.1.3 Tertiary Canals The selected system provides for total number of six tertiary canals, one off taking from each primary canal and secondary canal II and four off-taking from secondary canals I. 7.1.4 Quaternary Canals Quaternary canals are the smallest canals which off take from primary secondary and tertiary canals. The quaternary canals carry the full supply discharge for the area it is serving. All the water is diverted in to field channel of one field to irrigate the same. The layout of the quaternary canal is planned in such a way that it provides proper orientation of fields in proper direction of irrigation. There are 51 no. of quarterly cannels off taking from primary, secondary & tertiary canals. 20 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES 7.2 GCA AND CCA The area which can be economically irrigated from a scheme without considering the limitation of quantity of water is known as Gross Commanded Area (GCA). The Culturable Commanded Area (CCA) is that part of GCA where cultivation is possible. Therefore, the areas which are occupied by ponds, group of houses, alkaline soils, reserve forest, gully etc. are deleted from GCA to find CCA. For any new area proposed for irrigation about 10 to 15% of GCA is allocated for non agriculture purposes to be occupied by roads, canals, drains etc. At feasibility level about 4000 ha has been identified as CCA and scheme has been drawn up on the basis of this area However at detailed design stage the estimates of GCA and CCA have been reviewed as under: On field visit of the site it has been observed that a lot of area, much more is available on both banks of river in the downstream of proposed dam site which can be economically commanded from the storage created in the upstream side of the dam but the quantity of water is limiting factor which will decide the size of GCA and CCA. In the present case therefore an indirect approach is followed to work out the size of CCA and GCA as below Net Irrigation Requirement for 100 ha area =571.2 *103 m3 (refer table 9.15 of Sectoral Report on Agronomy) 3 Gross Irrigation Requirement for 100 ha area =571.2 ♦ 10 / 0.50 (assumed over all efficiency as 50%) = 1142.4* 103 m3 Water allocated for irrigation (75% availability) =38.484 Mm3 CCA (Culturable Commanded Area ) GCA( Gross Commanded Area) cultivable use ) =(38.484 ’10s m3)* 100/ 1142 4* 103 = 3368 7 ha say 3400 ha =3368.7/0.85 (15% area considered for non = 3963 ha say 4000ha 21 <■ Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES * The Gross Commanded Area of 4000 ha has been delineated on the basis of following ••4 considerations and indicated on the map appended with the report 1. Topography - favourable for extending gravity flow. Lands situated on the periphery having slopes more than 5% are excluded. 2. Agronomical potentials - good soils having adequate depths, suitable physical and chemical characteristics, water holding capacity, infiltration rates, permeability and free from erosion and salinity hazards. 3. Location - Accessible and closest to source of irrigation water. The command area is divided in two parts; first part lying in the head reach proposed to be served by primary canal. The command area in this part is a narrow belt, nearly 12 0 km long having 0.5 to 2.0 km. width After deleting unsuitable areas, the net CCA of this part works out to about 1000 ha. The command area beyond Dencho River is served by two secondary canals. This area comprise of bit wider belt of about 8 km length and 4 to 5 km width. The net CCA of this command works out to about 2400 ha. 7.3 Irrigation Intensity The percentage of CCA proposed to be annually irrigated is called Irrigation Intensity. Extensive irrigation is preferred to intensive irrigation on a smaller area on account of two reasons. Firstly quantity of water may be limited and secondly over irrigation entails harmful effects like water logging, soil salinisation etc. 22 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES A higher intensity may be allowed if an effective drainage system is provided in the irrigated area. In the present case 170 % intensity is assumed which comprises of 100 % during Meher season and 90 % in Belg season with 20 % annual crops 7.4 Night Irrigation The irrigation water is proposed to be supplied on a continuous basis through a system of main canals, secondary canals and tertiary canals which will run 24 hours In case, irrigation is provided in day time only for a period of 12 hours or so, night storage reservoir is necessary However, the day time irrigation only has not been recommended for the following reasons: In case of Gelana Irrigation project, a field size of about 48 hectare has been designed with the irrigation parameters and based on each watering at an interval of 13 days. With consideration of individual farm holding of about one hectare per family, there would be more or less 48 farmers in each field Individual irrigator will have a turn of watering in a 13 day cycle for his land of about one ha With this rotation of watering each farmer would get two turns to receive irrigation supply in one month; it may be once in night and once in day time. Thus individual farm requires 6 5 hours in day and 6.5 hours in night once in a month (13*24/48). It would not be difficult for the cultivator to work only 6.5 hours in the night once in a month against the huge saving to the Government exchequer on account of not providing the night storage irrigation reservoirs in the command. The layout has also been planned accordingly. Following disadvantages of night irrigation with the installation of night storage reservoirs are described below: i) The construction of the night storage irrigation reservoirs at the head of individual tertiary canal would add to the cost of the project. ii) Night storage irrigation reservoirs occupy substantial potentially irrigable land. For one cubic meter per second discharge in the canal, 12 hours storage of 1.5 meter deep night storage 23 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES reservoir would require permanent acquisition of about 3.00 hectare of command area land for each field unit, totaling a huge area to be acquired for the purpose. iii) Additional head would also be required in the canal system to provide water to the night storage irrigation reservoirs and moreover, these would be required to be constructed above the ground levels to provide operating head of water to run the distribution system situated below it This will add to the project costs. iv) In case of 12 hours’ irrigation, the distribution system in the downstream of the night storage reservoir has to carry double the discharge since it has to accommodate full day’s demand in 12 hours only which will add to extra cost. v) There would be additional day time evaporation loss of water in the night storage irrigation reservoirs in addition to the losses of water which are envisaged for design of canals which will affect the efficiency of irrigation. vi) It would be preferable for the cultivators to work during nights in hot weather conditions vii) The night storage irrigation reservoirs may be potential breeding reservoirs to the vectors of diseases like malaria and schistosomiasis. In view of above, night irrigation is proposed to be adopted in Gelana command area as per general practice in different parts of the world without any special arrangements of lighting in command areas. The farmers normally use torch lights to manage watering during night hours. Therefore no special arrangements of lighting are being proposed in the command area of this project 7.5 Irrigation Efficiencies As per International Irrigation and Drainage Committee the efficiency in use of water can be separated in to three components. 24 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES 7.5.1 Storage Efficiency It is the ratio of water diverted for irrigation or for any purpose and volume of water entering the reservoir. Losses in reservoir are caused by seepage, spillage from spillway and evaporation 7.5.2 Conveyance Efficiency It is the ratio of water reaching irrigation field and water diverted from the supply source. Conveyance losses comprise of seepage losses, evaporation losses (total called Absorption losses) and leakage loss from irrigation system. This is comprised of two efficiencies i.e conveyance efficiency of canals and conveyance ‘efficiency of field channels. For design of canal system assumed to 80 % and 90 % respectively giving total conveyancfe1 efficiency as 72 %. The conveyance losses of canals are worked on the basis of wetted perimeter of canal and absorption loss per million sq.m, of wetted area The absorption loss from field channel is taken as some percentage of water delivered to the field channel. Therefore both are considered separately. In detailed design of this project conveyance loss from canal system is assumed as 2.5 m3/s per million sq.m, of wetted parameter which are normal for the types of soils encountered in Erer command area The wetted perimeter for main canal is of the order of 6.0 m. Hence the absorption loss in main canal is taken as 15 0 lt/s per Km Similarly the wetted perimeter of secondary and tertiary canals is of the order of 3 0 m and therefore the absorption loss has been taken as 7.5 lt/s per Km length of these canals. 7.5.3 Field Application Efficiency It is the ratio of the volume of water used by plant by evapo transpiration and volume of water reaching the field. Water used in transpiration includes the effective rainfall also. This efficiency is assumed as 70 % considering 30 % loss. Total Efficiency of Water Use for Irrigation is multiplication of above three efficiencies. The overall efficiency of system is assumed as 50 % (0.8*0.9*0.7=50.5 say 50 % )Erer Dam & Irrigation Project /CECE & CES 8.0 Planning and Design of Canal Network 8.1 Canal Alignment The alignment of primary, secondary and tertiary canals had been marked on 1:4,000 scale map in such a way that primary canal and secondary canals are aligned as a contour canals and tertiary canals aligned as watershed or side slope canals for the purpose of the feasibility study. For detailed designs special strip surveys have been carried out along the proposed alignment of primary canal and secondary canals and topographical maps have been prepared having scale 1:4000 and contour interval 1.0m The alignment marked in the feasibility report has been transferred on the 1:4000 scale maps by adjusting the scale of map. The alignments as proposed in the feasibility report are found by and large in order excepting at places where some modifications have been carried out. The quaternary canals are generally aligned along watershed lines and are proposed to provide irrigation on both sides of their alignment. However in some cases it is not possible due to topographical limitations. In such situation they are aligned along contour lines and proposed to provide irrigation only on one side. The primary canal is generally carried on a contour alignment until it bifurcates in to two secondary canals so that these may command the full area to be irrigated The secondary canals are also planned on contour alignment on account of topographical reasons. As far as possible the Tertiary canals are taken off from main canal from or near the points where the parent canal crosses the watershed. The alignment of contour canals especially in upper reaches is decided after careful consideration of economy. Alternative alignments, their benefits and costs have been considered, while deciding the final alignment. Deep cuttings or high embankments have been avoided by suitable detouring. Careful judgments have been exercised in fixing the points of drainage crossing. 26 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES In sum, the alignments of primary canal and secondary canals as proposed in the feasibility report have been checked and are found to be generally in order excepting in some reaches where it has been modified. The general layout of the fields and the arrangement of tertiary, field canals have been made on the same line as that in the feasibility. However, some changes have been affected wherever necessary for the presence of natural drainage channels in the field orientations as verified from the detailed survey map of command area. Where the straight canal alignment is not possible for topographical reasons, simple circular curves with limiting radius have been provided as follows. 3 Capacity of canals (m /sec) < 0.3 0.3-3.0 3.0- 15 Limiting radius (m) 100 150 300 The canals are kept in balanced earthwork as far as possible for economic consideration. 8.2 Canal Design The Erer canal networks have been proposed as earthen channel. The requirement of lining to be provided in differant reaches are influenced by the classification and permeability of soils encountered along the canal alignment The observed data indicates that the soils encountered along the proposed alignments of primary and secondary canals are relatively impervious therefore no lining is proposed. Hydraulic sections of main canals, secondary canals and tertiary canals are designed as per Manning’s formula as stated in the design criteria keeping velocities in safe limits. Free boards, bank widths, cross roads, bank roads, side slopes, berms and dowels have been provided in accordance with the provisions made in the design criteria. 27 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES The quaternary canals are designed to have uniform cross section from head to tail. However primary canal, secondary canals and tertiary canals are designed to have telescopic section, reducing from head to tail depending upon the reduced discharge on account of off taking channels. 8.3 Design Criteria The design of earthen channels has been based on the following desgn criteria. Kennedy’s Theory, Lacy’s Theory and Manning’s Formula are used in design of earthen canals For canals of small discharging capacity such as in Erer Project not much change is going to happen in channel dimensions if worked out by either of the formula. Therefore on account of simplicity Manning’s Formula is used in designs of Erer Project. As per Manning’s Formula V=l/n*R S w lfl Where: V = Velocity in rn/sec R = Wetted Mean Radius = Cross section Area/wetted Perimeter S = Water Slope n = Manning Roughness Coefficient. (0.025 for main, branch and tertiary canals and 0.030 for field channels). The bed width and water depth ratio of the canals are normally based on Lacy’s Regime Theory However from practical considerations following criteria be adopted 3 Q < 0.5 m /sec B = D (in clay) B = 2D (in sand) 3 Q = 0.5 - 1.0 m /sec B = 2D (in clay) B = 3D (in sand) 3 Q = 1.0 - 5.0 m /sec B = 3D (in clay) B > 3D (in sand) Where B = bed width in m J 3 D = depth of water in mQ = discharge in m /sec 28 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES 8.3.1 Limiting Velocities a The higher the velocity, the smaller will be the section and thus affect the economy. But to avoid 4 siltation and scouring of earthen canals the following velocities may be adopted. Maximum velocity = 0.75 m/sec in all canals Minimum velocity = 0.25 m/sec in all canals 8.3.2 Working Head For preparing command statement and deciding the full supply levels in the different component of the canal system the following minimum working heads are required: o Head over field . = 15 cm o Head for field channel at its off take from quaternary = 15 cm o Head for quaternary in tertiary canal o Head for tertiary canal in the secondary canal o Head for secondary canal in the primary canal = 15 cm = 15 cm = 30 cm o Head for primary canal at main outlet (dam site) = 60 cm 8.3.3 Longitudinal Slope Lacy’s following regime equation for given discharge and silt factor provides guidance in choosing slope for unlined earthen channel. The same is used in computations of canal dimensions. S = 0.00031 (f3/2Q1/6) Where: S = longitudinal slope Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009 29 --Erer Dam & Irrigation Project ZCECE & CES 3 Q = discharge in m /s £3 f= silt factor =1.76 mrl/2 for silts, ^4 Very fine to fine, it varies from 0.4 to 1 Ojjg And for fine sands from 1.25 to 1.50 Where mr = average particle size of the boundary material In actual practice slightly steeper slope is provided than the one worked out by above equation. 8.3.4 Critical Velocity Ratio (CVR) it According to Kennedy for non silting and non scouring channels in steady regime there is only one velocity called ‘critical velocity’ denoted oy Vo, which is function of depth of water in r .t channel and obtained by following equation: *”>• Vo =0.546 D064 Where: Vo = critical velocity in m/s D = depth of water in meter ■» This equation was applicable to the grades of s’lt existing in the observation channel (in UBDC canal in Pakistan). To take in to account of varying silt grade another factor called ‘critical velocity ratio’ was introduced which is denoted by ‘m’ and the above equation was amended as below: V = 0.546m D064 Where: m = V / Vo = CVR Xi The value of m depends on type of silt. For channels carrying appreciable suspended loads, the value of m should be taken 1.10 at head and 0.85'towards tail end. In case of Erer Project, water is released from the reservoir and expected to be silt free and thus m will lie between 1.02 and 0.85. The same has been adopted in design i.e. in head reach 1.02 and in tail reach o 0.85 30 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES 8.3.5 Free Board The following minimum free board has been adopted in design of canals for different discharges indicated below: ------------------------- 3--------------------------------------------------- Discharge (m /sec) Minimum Free Board (m) <0.4 0.2 0.4-1.2 0.3 1.2-5.0 0.4 8.3.6 Bank Width As per Indian Standard Code of Practice IS: 7112-2002 titled “Criteria for Design of X-Section for Unlined Canals” the recommended top width of bank is 1.5 m for discharge 0.15 to 7.5 m3/s for non inspection bank and 5.0 m for inspection bank. The same is adopted in design of canals in Erer project. 8.3.7 Saturation Gradient Types of Soils Saturation Gradient Clayey Loam 1:4 Sandy Loam 1:5 The top width of canal banks indicated above is absolutely minimum as required from stability considerations only. However if functional requirement is integrated with the stability considerations, the width of canal banks will change. Ensure a minimum cover of 0.5m on saturation line 31 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES 8.3.8 Inspection Roads The alignment of inspection roads of main canal and secondary canals shall be planned on their left banks as all the head regulators of off-taking channels are located on the left banks only. These roads will provide free excess to regulatory structures for their inspection and maintenance which otherwise will not be possible from roads on right side without provision of bridges on each site Bank Side Slopes for Main Canal Type of Soil Side Slopes Cutting Filling Loamy Soils 1 : 1 1.5 : 1 Sandy Soils 1.5 1 2: 1 For tertiary canals and field channels cutting and filling slopes have been kept 1.5:1. The bank slopes indicated in the above table are only generalized values which are found adequate in majority of cases. However in extreme cases when the banks are too high the stable slopes have been checked for stability to withstand following conditions during operation of canals: (1) Sudden drawdown condition for inner slopes (2) Water running full with banks saturated with rainfall for outer slopes. 8.3.9 Canal Embankment Material For canal embankment materials following criteria are used: o Liquid limit > 25% o Plasticity index > 10% o Gypsum <2% (to avoid solution holes) o Sulphate < 0.2% (to avoid sulphate attack on ordinary Portland Cement) 32 Annex E /irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES 8.3.10 BERM Berm is the horizontal space left at ground level between the toe of the bank and excavation. Following criteria shall be used for location and size of berms in different situations. (1) When Full Supply Level(FSL) is above Natural Surface Level( NSL) and bed level is below NSL i.e. the canal is partly in cutting and partly in filling, berm is provided having 2D width at the NSL, where D is full supply depth of canal. (2) When FSL and bed level are above NSL i.e. canal is fully in filling the berm of 3D width is kept at FSL. (3) When FSL and bed level are below the NSL i.e. the canal is in full cutting, the berm having width 2D is provided at FSL 8.3.11 Catch Water Drain For the canals excavated on the slopping ground along contour, a catch water drain, having designed carrying capacity to carry expected discharge of flood from its catchment and leading to natural stream, is required to be provided. These drains are designed to carry overland flow from the area where regular drains do not exist. In this project the catch water drains of 1.0m width and 1.0 m depth having side slopes of 1:1 are recommended. These drains are proposed on upland side of primary canal and both the secondary canals. The drains shall outfall in to natural drains crossing the canals 33 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES 8.4 Command Area And Design Discharges For Quaternary Canals There are total 51 number of quaternary canals Out of these 16 off take directly from primary canal and 7 and 14 offtake directly from secondary canal-I and secondary canal-II respectively. However 14 number offtake from the tertiary canals. The alignments of all the quaternary canals are finalised on the basis of topographical parameters. The areas proposed to be commanded by these quaternary canals are measured from the map. The following table gives the areas served by each quaternary canal and tertiary canal. Table 8.1 Culturable Command Area and Design Discharges for Quaternary Canals taking off from Primary Canal Chainage (km + m) Canal Name Canal Length (km) Area Covered (ha) Discharge (l/sec) Design Discharge (l/sec) 1+100 Q1P 1.40 35 19.25 22.14 2+300 Q2P 1.00 30 16.50 18.98 3+430 Q3P 1.30 60 33.00 37.95 3+700 Q4P 1.50 55 30.25 34.79 4+200 Q5P 2.30 85 46.75 53.76 5+600 Q6P 1.40 45 24.75 28.46 6+000 Q7P 1.40 55 30.25 34.79 6+400 Q8P 1.20 40 22.00 25.30 7+200 Q9P 1.20 60 33.00 37.95 7+600 Q10P 1.20 55 30.25 34.79 8+300 Q11P 0.90 45 24.75 28.46 8+850 Q12P 1.20 33 18.15 20.87 9+400 Q13P 3.00 80 44.00 50.60 10+100 Q14P 1.30 45 24.75 28.46 10+900 Q15P 2.10 60 33.00 37.95 12+950 Q16P 1.60 70 38.50 44.28 sub total 24.00 853.00 469.15 539.52 34 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES Table 8.2 Culturable Command Area and Design Discharges for Tertiary & Quaternary Canals Taking off from Primary Canal Chainage (km + m) Canal Name Canal Length (km) Area Covered (ha) Discharge (l/sec) Design Discharge (l/sec) 12+900 T1P 1.00 175 96.25 110.69 12+900 Q1T1P 1.70 75 41.25 47;44 12+900 Q2T1P 1.20 40 22.00 25.30 12+900 Q3T1P 1.50 60 33.00 37.95 Sub total 175 96.25 110.69 Note: the discharge of the tertiary canal is the sum of the quaternary canal (the same is true for the area) Length of primary canal = 13600 m Absorption loss of primary canal 15 lit/sec per km length of canal Table 8.3 Culturable Command Area and Design Discharges for Quaternary and Tertiary Canals Chainage (km + m) Canal Name Canal Length (km) Area Covered (ha) Discharge (l/sec) Design Discharge (l/sec) 1+900 T1S1 2.10 255 140.25 161.29 0+950* Q1T1S1 1.35 55 30.25 34.79 1+275* Q2T1S1 1.50 50 27.50 31.63 1+700* Q3T1S1 1.30 65 35 75 41.11 2+100* Q4T1S1 3.10 85 46.75 53.76 2+500 Q1S1 1.80 90 49.50 56.93 3+300 Q2S1 1.10 35 19.25 22.14 3+900 Q3S1 1.30 40 22.00 25.30 4+450 Q4S1 2.20 75 41.25 47.44 5+000 Q5S1 2.20 65 35.75 41.11 5+500 Q6S1 2.20 100 55.00 63.25 6+750 T2S1 3.00 190 104.50 120.18 2+300* Q1T2S1 0.50 20 11.00 12.65 2+600* Q2T2S1 25 13.75 15.81 2+800* Q2T2S1 1.00 .30 16.50 18.98 7+200 Q7S1 3.50 135 74.25 85.39 7+700 T3S1 0.70 130 71.50 82.23 0+700* Q1T3S1 1.90 . 95 W 52:25 60.09 8+200 T4S1 0.70 130 71.50 82.23 0+700* Q1T4S1 1 90 95 52.25' 60.09 sub total 1245 684.75 787.46 35 Annex E : Irrigation & Drainage Design /Final Detail' Design Report /2009Erer Dam & Irrigation Project /CECE & CES * quaternary canal length started from Tertiary canal Table 8.4 Culturable Command Area and Design Discharges for Quaternary and Tertiary Canals Taking off from Secondary Canal Two Chainage (km + m) Canal Name Canal Length (km) Area Covered (ha) Discharge (l/sec) Design Discharge (l/sec) 0+350 Q1S2 0.80 30 16.50 18.98 1+500 Q2S2 1.20 40 22.00 25.30 3+200 Q3S2 1.80 80 44.00 50.60 4+000 T1S2 0.10 105 57.75 66.41 4+000 Q1T1S2 1.70 . 60 33.00 37.95 4+000 : Q1T1S2 1.20 45 24.75 28.46 5+650 Q4S2 3.10 60 33.00 37.95 6+500 Q5S2 3.00 110 60.50 69.58 7+000 Q6S2 2.00 105 57.75 66.41 7+500 Q7S2 2.20 110 60.50 69.58 8+600 Q8S2 1.30 60 33.00 37.95 9+100 Q9S2 1.50 50 27.50 31.63 9+775 Q10S2 1.60 65 35.75 41.11 10+350 Q11S2 1.50 70 38.50 44.28 11+550 Q12S2 1.10 40 22.00 25.30 11+900 Q13S2 0.90 40 22.00 25.30 12+400 Q14S2 1.00 50 27.50 31.63 sub total 26.00 1015 558.25 641.99 total length of secondary canal two is 12+400 km 8.5 Calculations of Design Capacities 8.5.1 Quaternary Canals (off- taking from any Tertiary canal or directly from Primary or Secondary Canal) Discharge required at the head of Quaternary Canal = CCA of quaternary Canal *0.498/0.9 The section of Quaternary canal shall remain the same in its entire reach from head to tail and connected to the nearby natural drain to dispose off surplus discharge. 36 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES The flexibility of 15% is kept in entire canal system to account for the poor maintenance conditions. If the canal is not maintained in good condition and there is deposition of silt and growth of weeds, the rugosity coefficient is changed and discharging capacity is reduced It is desirable to make sufficient allowance for this purpose. In Erer project this allowance is kept as 15%. 8.5.2 Tertiary Canals (off-taking from Secondary Canal or directly from Primary canal) Discharge at the head of any tertiary canal = Discharge required at head of all off-taking Quaternary Canals+ absorption loss in Tertiary canal. The absorption loss in Tertiary canal is taken@7.5 1/s/km length of tertiary canal Design Discharge at Head of any Tertiary canal is multiplied by 1.15 to account for flexibility The Design section of Tertiary canal shall reduce from head to tail depending on the discharge of off-taking Quaternary canals. 8.5.3 Secondary Canals ( Off-taking from Primary Canals) Discharge required at Design section of Tertiary canal shall reduce from head to tail depending on the discharge of off-taking Quaternary canals. The discharge at head of Secondary Canal is equal to total required discharge of the off-taking canals i.e. tertiary canals and quaternary canals directly off-taking from secondary canal plus losses in Secondary canal taken @ 7.5 lt/s per km length of secondary canal Design discharge at the head of secondary canal is found out by multiplying the discharge arrived as above by 1.15 to take in to account the flexibility. The design section of secondary canal shall reduce from head to tail depending on the discharge of off-taking canals. 37 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES 8.5.4 Primary Canal Similarly the discharge of the Primary canal at Head is equal to total required discharge of all off- taking canals i.e. secondary canals, tertiary and quaternary canals directly off taking from primary Canal plus losses in Primary Canal head to tail taken as @ 15 lit/s per km length of primary canal. Design discharge at head of Primary canal is equal to the discharge worked out above multiplied by 1.15 factor. Like secondary canal the design section shall reduce from head to tail depending upon the discharge of the off-taking canals. Capacity of Secondary canal-I (CCA=1345 ha) Net irrigable area = 1345 ha Peak irrigation requirement of plant = 0.349 1/s/ha Field application efficiency = 0 7 Peak irrigation requirement at field=0.349/.7 = 0.49857 1/s/ha Peak irrigation requirement at the head of quaternary canals = 0.49857/0.9 = 0.553961/s/h Loss in secondary canal (8.366 km) and tertiary canal (5.3 km) = 13.666*7.5 = 102.45 1/s Water required at the head of secondary canal-I = 1345*0.55396+102.45 = 847.52 1/s 38 ^Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES Increase this capacity by 15% for flexibility The design capacity of secondary canal-I at head =847.52*1.15 =974.65 I/s =0.974 m3/s On the same basis the design capacities of primary canal and secondary canal-H at their heads have been worked out which come to 2.709 m /s and 0.773 m /s respectively. 8.5.5 Capacity Statements for Different Reaches Before designing the canals, the capacity statements have been prepared giving the reach of canal under consideration, discharge at head of reach, conveyance losses in this reach, name of off- taking channel, its CCA and its required discharge. After deducing this discharge the discharge of the next reach has been worked out. This statement is also known as cut-off statement. Table 8.5 Statement showing Total discharge utilized in different Canal systems 3 3 S.No Name of Canal CCA (ha) Water diverted in Quaternary and Tertiary’ canals (1/s) Length of Canals (km) Absorplio n loss in canal (Vs) Length of Tertiary canal (km) Absorption loss in tertiary canal 1/s Total water utilized (Vs) 1 Primary Canal 1022 562.1 13.392 200.88 1.30 9.75 772.73 2 Secondary Canal-I 1345 739.75 8.366 62.74 5.30 39.75 84224 3 Secondary' Canal-Il 1042 573.1 13.10 98.25 0.1 0.75 672.05 Total 3409 1874.95 34.858 361.87 6.7 50.25 2287.02 Design Capacity of primary canal = 2.356 xl.15 = 2.709 m /s 3 Design Capacity of SI Design Capacity of S2 = 0.842 x 1.15 = 0.96S m3/s = 0.672 x 1.15 = 0.773 m3/s 39 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES Table 8.6 Capacity Statement of Primary Canal S.N 0 Reach (m) Discharge at the head of reach (m /s) Lengt h of reach (km) Seepage less in reach (m /s) Name of off-taking channels 3 3 Discharge diverted in off-taking channels (m /s) Discharge at the tail of reach (m /s) Design discharge of the reach (m /s) 3 3 3 1 2 3 4 5 6 7 8 = Col 3-5-7 9= 1.15 x Col 3 1 0+0 to 2+200 2.356 2.2 0.033 QiP.QzP 0.071 2.252 2.709 2 2+200 to 3+600 2.252 1.4 0.021 QjP. Q4P 0.061 2.170 2.590 3 3+600 to 5+400 2.170 1.8 0.027 Q5P, Q6P 0.074 2069 2.49 4 5+400 to 6+250 2.069 0.85 0.013 Q7P, QgP 0.052 2.004 2.38 5 6+250 to 7+500 2.004 1.25 0.019 Q»P,QioP 0.063 1.922 2.30 6 7+500 to 8+700 1.922 1.2 0.018 Qll+Ql2 0.055 1.849 2.21 7 8+700 io 9+900 1.849 1.2 0.018 Ql3+Ql« 0.096 1.735 2.12 8 9+900 to 13+394 1.735 3.49 0.052 Qis+TiP 0.131 1.552 2.00 Table 8.7 Capacity Statement of Secondary Canal - I S.N 0 Reach (m) Disch ar ge at the head of reach (m’/s) Lengt hof reach (km) Seepage loss in m’/s @ 7.5lt/s/ km Lengt hof Tertiar y Canal in reach (km) Secpag e loss in Tertiar y Canal (m’/s) Name of OCT-taking channel Discharge diverted in off taking channels (m’/s) Dischar ge of die tail of reach (tn’/s) Design Discha rge (“7 s) 1 2 3 4 5 6 7 8 9 10 11 1 0+0 to 1+500 0.842 1.5 0.011 1.6 0.012 T1S1 0.154 0.665 0.968 2 1+500 to 3+000 0.665 1.5 0.011 - - Q1S1 and Q2St 0.082 0.572 0.765 3 3+000 to 4 +400 0.572 1.4 0.01 - - Q3S1 and Q«Si 0.077 0.485 0.660 4 4+400 to 5+500 0.485 1.1 0.008 - - Q5S1 and Q6Si 0.104 0.373 0.557 5 5+500 to 7+050' 0.373 1.55 0.012 2.30 0.017 T 2Si and Q7S1 0179 0.165 0.429 6 7+050 to 7+550 0.165 0.5 0.004 0.7 0.005 TaS, 0.0715 0.084 0.189 7 7+550 to 8+366 0.084 0.82 0.006 0.7 0.005 T.Sl 0.0715 0.001 0.116 40 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES * Table 8.8 Capacity Statement of Secondary Canal - II S.N 0 Reach (m) Discharge al the head of reach (m’/a) Length of reach (km) Seepage loss in m’/s @ 7.51t/s/km Length of Tertiary Canal in reach 0“"). Seepag e loss in Tertiar y Canal (m’/s) Name of off-taking channel Discharge diverted in off- taking channels (m’/s) Discharge oflhetail ofreach m’/sec Design Discharge m’/sec 1 2 3 4 5 6 7 8 9 10 11 1 0+0 to 1+500 0.672 1.5 0.012 - - Qi S?and QzS; 0.0467 0.613 0.773 2 1+500 to 3+500 0.613 2.0 0.015 1.3 0.01 Q S and TiS 32 2 0.115 0.483 0.705 3 3+500 to 5 +600 0.483 2.10 0.016 - - Q4S2 and Q S 52 0.103 0.364 0.555 4 5+600 to 6+600 0.364 1.0 0.007 - - Q S and Q7S2 62 0.096 0.261 0.418 5 6+600 to 8+200 0.261 1.6 0.012 - - Qs S2 and Q9 S2 0.057 0.192 0.300 6 8+200 to 9+600 0.192 1.4 0.010 - - Q10 S2 and Qu S? 0.082 0.100 0.221 7 9+600 to 10+700 0.100 1.1 0.007 - - Qi 2 S2 and Qi 3 S2 0.046 0.047 0.115 8 10+700 to 13+100 0.047 2.4 0.018 - - Qi 4 S2 0.024 0.005 0.054 Table 8.9 Hydraulic Parameters-Primary Canal Reach (km) Discharge (m’/s) n Slope (m/m) Depth (m) B.W. (m) W.P. (m) V(m/s) Vo=0.55Dum CVR F.B (m) 0.0-2.2 2.709 0.025 00035 1.10 2.50 6.47 0.59 0.58 1.01 0.40 2.2-3.60 2.59 0.025 00035 1.07 2.50 6.37 059 0.57 1.01 0.40 3.60-5.40 2.49 0.025 0.0035 1.05 2 50 6.30 0 58 0.566 1.02 0.40 5.40-6.25 2.38 0.025 00035 1.04 240 6.17 0.57 0.563 1.01 0.40 6.25 -7.50 2.30 0.025 0.0035 1.03 2.40 6.10 0.57 0.56 1.01 0.40 7.50-8.70 2.21 0.025 0.0035 1.01 2.40 6.02 0.56 0.553 1.01 0.40 8.70-9.90 2.12 0.025 0.0035 1.0 2.30 5.91 0.56 0.55 1.01 0.40 9.90-13.394 (tail 2.00 0.025 0.0035 1.0 2.13 5.73 0.55 0.55 1.00 0.40 Annex E : Irrigation &Drainage Design /Final Detail Design Report /2009 • >Erer Dam & Irrigation Project ZCECE & CES Table 8.10 Hydraulic Parameters-Secondary Canal I Reach (Km) Discharge 3 Q m /sec n Slope (m/m) Depth (m) B.W. (m) W.P.(m) V(m/sc c) Vo = 0.55D 0.64 CVR F.B (m) 0-1.50 0.968 0.025 0.0004 0.82 1.20 4.14 0.49 0.488 1.0 0.30 1.5-3.0 0.765 0.025 0.0004 0.74 1.16 3.81 0.46 0.459 1.0 0.30 3.0-4.4 0.650 0.025 0.0004 0.69 1.15 3.63 0.44 0.44 1.0 0.30 4.4-5.5 0.557 0.025 0.0004 0.64 1.10 3.39 042 0.4207 0.998 0.30 5.5-7.05 0.429 0.025 0 0004 0.58 1.00 3.08 0.40 0.3966 1.00 0.20 7.05-7.55 0.189 0.025 0.0004 0.41 0 80 2.29 0.32 0.322 0.99 0.20 7.55-8.366 0.116 0.030 0.00045 0.33 0.75 1.94 0.28 0.2827 0.99 0.20 Table 8.11 Hydraulic Parameters-Secondary Canal II Reach (km) Discharge (m /s) n 3 Slope (in/m) Depth (m) B.W. (m) W.P. (m) V(m/ sec) Vo = 0.55D 0.64 CVR F.B (m) 0-1.50 0.773 0025 0.0004 0.74 1.15 3.82 046 0.4590 1.0 0.30 1.5-3.50 0.705 0.025 0.0004 0.72 1.08 3.68 0.45 0.4516 0.996 0.30 3.50-5.60 0.555 0.025 0.0004 0.64 1.08 3.39 0.42 0.420 1.0 0.30 4.60-6.60 0.418 0.025 0.0004 0.57 1.0 3.06 0.39 0.3925 0.99 0.20 6.60-8.20 0.300 0.025 0.0004 0.50 0.90 2.71 0.36 0.3628 0.99 0.20 8.20-9.60 0.221 0.025 0.0004 0.43 0 88 2.44 0.33 0.3314 0.99 0.20 9.60-10.70 0.110 0.025 0.0004 0.33 0.60 1.79 0.28 0.2828 0.99 0.20 10.70-13.10 0.054 0.030 0.00045 0.25 0.42 1.31 0.24 0.239 1.00 0.20 42 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES Table 8.12 HYDRAULIC PARAMETER -T4S1 Reach (km) Q (m /s) N 3 Slope (m/m) Side slope (h/v) Depth (m) B.W. (m) W.P (m) V M/sec V0 = 0.55D CVR FB (m) 0.64 0-0.700 0.088 0.025 0.00045 1.5:1 0.32 0.45 1.62 0.28 0.312 1.01 0.20 Table 8.13 HYDRAULIC PARAMETER -T1S2 Reach (m) Q (m3/s) N Slope (m/m) Side slope (h/v) Depth (m) B.W. (m) W.P. (m) V (m/s) Vo = 0.55D CVR =V/Vo F.B. (m) 0.64 0-0.10 0.069 0.025 0.00045 1.5:1 0.29 0.45 1.51 0.26 0.2616 0.99 0.20 Table 8.14 HYDRAULIC PARAMETER -TiP Reach (m) Q (m3/sec) N Slope (m/m) Side slope (h/v) Depth (m) B.W. (m) V (m/s) Vo = 0.55D <>•<* CVR F.B. (m’ 0-1.30 0.154 0.025 0.00045 1.5:1 0.41 0.53 0.32 0.3221 0.993 0.20 Table 8.15 HYDRAULIC PARAMETER -TiSi Reach (m) Q (m3/sec) N Slope (m/m) Side slope (h/v) Depth (m) B.W. (m) V (m/s) vo = 0.55D o CVR F.B. (m) 0-1.60 0.126 0.0 25 0.00045 1.5:1 0.39 0.48 0.31 0.3126 0.992 0.20 43 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES Table 8.16 HYDRAULIC PARAMETER -T Si 2 Reach (m) Q (m3/s) N Slope (m/m) Side slope (h/v) Depth (m) B.W. (m) V (m/s) Vo = 0.55D CVR F.B. (m) 0-2.30 0.072 0.025 0.00045 1.5:1 0.30 0.46 0.27 0.2671 1.01 0.20 Table 8.17 HYDRAULIC PARAMETER -T3S1 Reach (m) Q (m3/s) N Slope (m/m) Side slope (h/v) Depth (m) B.W. (m) V (m/s) Vo = 0.55D 0 M CVR F.B. (m) 0-0.70 0.072 0.025 0.00045 1.5:1 0.30 0.46 0.27 0.2671 1.01 0.20 S= 0.0003 l^Q ' 8.6 Procedure Adopted for Design Following procedure has been adopted for design of earthen canals: (1) Lacey’s regime slope has been found by using following formula, 1 6 ) for primary canal Q=2.709 n?/s and f=1.0 The slope is worked out to 0.00036. The slope of primary canal has been considered as O.OOO35 in calculations (2) Appropriate values of B and D assumed. (3) Velocity calculated by Manning’s Formula using appropriate value of rugosity coefficient (0.025 in this case ) (4) Critical velocity Vo calculated by using Formula Vo^.SSD0 64 (5) Calculations were continued till the selected value of D and computed value of V satisfy the critical velocity ratio (CVR) ______________________________________________________________________ 44 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES 9.0 Irrigation Structures The detailed design of irrigation and drainage structures are earned out in two phases. In first phase hydraulic designs are carried out which are intended to determine the optimal location, configuration of components of hydraulic structures, waterway requirement, protection against sour, seepage and uplift pressures, energy dissipation arrangements etc. In second phase Structural designs are carried out which aims at evaluating the forces/ stresses on each component of structures on account of dead loads, dynamic loads, seismic loads and earth pressures and each component is designed to resist the forces and bending moments caused by all these loads. The canal structures are hydraulically designed as per aforesaid design criteria set out for Erer project. The detailed structural designs are carried out as per detailed procedures in vogue internationally 9.1 ESCAPE Structures These are the structures meant for escaping surplus or excess water for the purpose of safety of canal and its structures and depleting the canals for repair and maintenance purposes There are two types of escapes, Weir Escapes and Sluice Escapes 9.1.1 Choice of Types of Escape Weir Escapes are constructed in masonry or cement concrete with or without crest shutters capable of escaping surplus water from canal. Sluice Escapes however comprise of a head regulator of sluice escape, cross regulator on canal located just downstream of location of escape (if entire discharge of the canal is required to be escaped) and escape channel. Sluice escape besides removing surplus water act as scouring sluice and helps to remove silt from the canal. Sluice 45 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES escapes are therefore preferred over weir escapes generally unless site conditions limit the use of weir escapes. Surface escapes may be used in case of an escape opposite an inlet when an inlet does not bring considerable amount of silt Surface escapes also become useful at the tail end of canal where there are fluctuations in withdrawals from canal and excess quantity of water can be suitably disposed off Sluice escapes are necessary where the canal is required to be emptied quickly. Sluice escapes become essential when the inlet can bring considerable amount of silt. After considering all the above said points in Erer project, it is proposed to go with for sluice type of escape with out any crest so that the canal may be emptied fully to facilitate repair works The escape is proposed to be designed as a simple flat regulator. 9.1.2 Criteria for Location Following criteria are adopted: • The location of escape is decided by availability of suitable drain, depression or river with bed level at or below canal bed level for disposing off surplus water through escape directly or through escape channel. • Provision of escapes at every 15 to 20 km is desirable on main canals and 10 to 15 km on secondary canals. • Escapes may be located at up-stream of major structures such as aqueducts, railway crossings, major diversion structures etc. • Escapes may be provided in combination with aqueducts or siphons for affecting the economy. • Escapes are necessary at important points where branches lake off from main canal or several distributaries take off from branch canal. In case of lift channels escapes are essential up-stream of pumping station. • When canal is very close to the edge of river bank, its bed level near the head works being considerably lower than the flood plain of the river, there is a risk of flood flow entering in to canal by way of breaches If there is no escape provided the canal system may be 46 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES severely damaged by excessive flow. The escape may be located at a point downstream of the reach where canal bank is vulnerable to the flood damage to restrict the damage to the reach upstream only. • When the canal runs along the steep side of the hill or along a steep bank of a comparatively soft material, an escape may be located at the upstream end of the canal section where it first approaches a steep bank. In case of a land slide occurring in the hill slope the entire canal may be blocked resulting in abrupt rise of water level in the upstream for a considerable distance. This intern can cause extensive damage to canal section. An escape provided at a suitable place on the upstream of such reach would act as a safety plug to arrest the rise of water level and avoid consequential effects. • When canal is confined by bank on one side and the unbanked side allows surface inflow, escapes need to be provided at appropriate location in the vicinity to dispose of the water so received. • Escapes opposite the inlets or at a nearest suitable location may be needed whose drainage water is let into the canal without reserve capacity to receive such water over and above the authorized full supply discharge of the canal. • Certain quantity of heavy bed silt may find its way through the regulator into head reach of canal and thereby reduce the water way. In such cases sluice escape within 5 km of canal head reach may be provided. After having considered above points the location of the proposed escape is decided at about 4+150 chainage point of primary canal where it crosses a sizeable drain designated as CD5P ( Estimated Q 5=15.8 m /s ) which outfalls in River Erer. 2 3 9.1.3 Criteria for Escapes Capacity The flow requirement to be diverted through escape may vary from small quantities to total discharge of canal. No general rules are laid for deciding the discharge capacity of escape. The criteria are location and requirement specific. Following guidelines are adopted: 47 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES • If the canal passes near important town or important installations where breach of canal can affect costly properties or human lives the capacity of escape should be equal to maximum flow which can pass in the canal. In other cases it should seldom be greater than the half of discharge of canal or not less than the difference between maximum discharge of canal at the proposed escape site and maximum flow at next escape • When the escape is used mainly to empty the canal for maintenance, the capacity should be fixed taking into account the number of days in which the canal is to be emptied. • In general the design capacity of escape is normally taken to be 50 to 60% of canal discharge at the point of escape. After considering above issues the capacity of proposed escape of Erer Project is proposed to 60 % of the capacity of canal at the site of escape 9.1.4 Design Considerations The structural as well as hydraulic design criteria adopted in this case are the same as that of other simple flat regulators. • The safety of escape structure has been checked for exit gradient. The maximum exit gradient has been worked out on the basis of difference in maximum water level in canal and minimum water level in escape channel. • The escape structure has been checked for safely against uplift pressure and sliding. • The required water way has been computed by using broad crested weir formula with appropriate discharge coefficient considering the conditions of flow. • In this escapes the sill is kept at the bed level of primary canal. This will enable quick emptying of canal and silt removal besides providing economical waterway. • The safety arrangements have been made adequately to cater for all flow conditions and operation • Adequate protection works have been provided on down stream side of structure same as in case of other regulatory structures 4S Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES 9.2 Canal Head and Cross Regulators A head regulator is provided at the head of channel, which controls the supplies entering into channel. A cross regulator on the other hand is located at the down stream side of an off taking point on main channel to head up water level to enable the off-taking channel to draw the required supplies. Head regulators also control the entry of silt into distributaries besides serving as meter for measuring discharges. There are two head regulators provided in the system. These are head regulators of both the secondary canals off-taking from the tail of primary canal. One acts as cross regulator to the other regulator and vice versa. These have been designed as per design criteria Since the sizes of parent channel and off-taking channels are very small, only one bay of regulators are considered adequate and no piers are provided. The structure has been checked for exit gradient and adequate length of floor and downstream cut off wall have been provided for safe value of exit gradient. Bligh’s coefficient has been assumed as 7 and accordingly length of floor is worked out. The thickness of floor provided is sufficient to resist uplift pressure. The uplift pressure is to be calculated in following two conditions: (a) When upstream water level is headed up to full supply and off-taking channel is dry (b) When the upstream water level is headed up to full supply and varying discharge pass down stream. The upstream cut-offs have been provided up to Lacey’s scour depth below the upstream bed level or ground level, which ever is low. Channel Capacity (m /sec) 3 Minimum Depth of Cut off (m) Up to 3.0 1.0 3.1 to 30 1.20 49 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES_________________________________ * . • The downstream cut-offs have been provided from safe exit gradient considerations Channel Capacity (m /sec) J Minimum Depth of Cut off (m) Up to 3.0 1.0 3.1 to 30.0 1.20 When the available working head in off taking canal is more than half of the full supply depth in parent channel, cross regulator may not be provided in conjunction with head regulator. 9.3 Outlet Structures: It is a device through which water is released from a distributing channel to quaternary canal. Out let must full fill following requirements o It shall be structurally strong and shall have no moving parts so that ■ It does not require periodic attention ■ It is not tampered by farmers or unauthorized persons o It shall draw its fair share of silt carried out by parent channel o It shall work efficiently with small working head. o It shall be economical. Various types of canal out lets have been evolved from time to time to obtain suitable performance. No one has come out to be suitable universally. In fact it is very difficult to achieve good design with respect to flexibility and sensitivity because of various indeterminate conditions both in distribution channels and the water courses, namely, discharge levels, silt charge, capacity factor, rotation of channels, regime condition of distributing channels etc affect their functioning. Even a particular outlet considered suitable upstream of control structure in a channel may not remain suitable at a considerable distance on the same channel. In Erer irrigation scheme pipe outlets are proposed to be used. The pipes are placed horizontally and at right angle to the centre line of the distributing canal. Discharge through the pipe outlet is given by formula; 50 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009 Erer Dam & Irrigation Project ZCECE & CES Q=CAy[2gH Where C = Coefficient of discharge which depends on friction factor, length and size of pipe outlet. I* A r 15d } P L ' 40^ f= coefficient of fluid friction for pipes, its value would be 0.005 for clean iron pipe and 0.01 for slightly encrusted pipe L= Length of pipe in meters D= diameters of pipe in cm H= Head of water measurement form central line of pipe to the FSL In Erer irrigation project steel pipes are proposed to be used for outlets assuming slightly encrusted (f=0.01) for design purposes. It is proposed to place the pipes at bed of the distributing channel to enable the outlet to draw its fair amount of silt The inlet and exit ends of pipe are proposed to be fixed in stone masonry to prevent its tempering Table given below gives discharges for different heads and different diameter of steel pipes. The sizes of outlet pipes are selected from the table given below. Table 9.1 Discharges of pipe outlets for different Heads Coefficient of Friction f= 0.01 Length of the pipe m Diameter of< pipes cm Discharge Q in Cumecs 0.20m 0.30m 0.40m 0.50m 0.75m 1.0m 3 10 15 20 ’ ' 25 0.009 5 0.023 1 0 043 0 0.069 0 0.011 6 0.028.3 0.052 5 0.084 4 0.013 4 0.032 7 0.060 7 0.097 7 0.015 0 0.036 5 0.067 9 0.109 2 0.018 4 0.044 8 0.083 0 0.134 0 0.021 2 0.051 6 0.096 0 0.154 4 51 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009 <Ercr Dam & Irrigation Project /CECE & CES *♦ Length of the pipe m Diameter of pipes cm Discharge Q in Cumecs 0.20m 0.30m 0.40m 0.50m 0.75m 1.0m 5 10 15 20 25 0.008 3 0.020 8 0.039 4 0.064 1 0.010 2 0.025 5 0.048 0 0.078 3 0.011 8 0.029 4 0.055 6 0.090 6 0.013 2 0.032 9 0.062 0 0.101 3 0.016 0 0 040 2 0 076 0 0.123 9 0.018 6 0.046 5 0.087 9 0.143.3 7 10 15 20 25 0.007 47 0.019 1 0.036 5 0.060 1 0.009 16 0.023 4 0.044 6 0.073 4 0.010 6 0.027 0 0 051 6 0 084 9 0.0119 0.030 2 0.057 6 0.095 0 0.014 5 0.037 1 0.070 6 0.1162 0.016 8 0 042 6 0 081 6 0.134 4 9 10 15 20 25 0.006 86 0.017 7 0.034 2 0.056 7 0.008 42 0.021 7 0.041 8 0.069.3 0.009 74 0.025 0 0.048 3 0.080 2 0.010 9 0.028 0 0.054 1 0.089 6 0.013 4 0.034 3 0.062 3 0.109 6 0.015 4 0.039 6 0.076 4 0.126 8 12 10 15 20 25 0.006 17 0.016 1 0 031 5 0.052 6 0.007 56 0.019 8 0.038 5 0.064 4 0.008 76 0.022 8 0.044 5 0.074 4 0.009 8 0.025 5 0.049 7 0.083 2 0.012 0 0.031 3 0.060 9 0.101 7 0 013 9 0.036 0 0.070 4 0.117 7 15 10 15 20 25 0.005 66 0.014 9 0.029 4 0.049 2 0.006 94 0.018 2 0.035 9 0.060 1 0.008 03 0.021 0 0 041 5 0.069 6 0.009 0 0.023 5 0.046.4 0.077 8 0.011 0 0.028 8 0.056 8 0.095 0 0.012 7 0 033 3 0.065 7 0.110 1 A typical drawing of outlet structure has been given in Drawing Volume 52 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES 9.4 Drop Structures Canals are constructed with permissible bed slopes so that the velocity of water in the canal will neither produce scouring nor silting of the canal. It is not always possible to carry the canal along the ground slope unless heavy earth work is done. This will be unwise and uneconomical. Hence, it becomes imperative that at suitable position, the canal bed is given a vertical or inclined drop. Drop structures are provided on the ridge section of canals where bed level gradient is less than the existing land slope available along the ridge line. The difference is adjusted by constructing suitable drop structures at suitable interval In main canals, which do not irrigate adjacent lands directly, the drop structures are located from the consideration of economy in cost of excavation the channel. The drop structures are located in relation to ground level and channel bed level so as to balance cut and fill between reaches as far as possible. In secondary or tertiary canals, which irrigate surrounding lands, the drop structures are located in such a way that they don’t cause any loss of command. The full supply level in the channel may be so marked that it covers all the command points and allows a minimum working head of 0 15 m for off- taking regulators and outlets. Location and Design Criteria The Location depends upon the ground conditions of the area through which the canal is flowing and the type of canal. o In main canals, which do not irrigate adjacent lands directly, the drop structures are located from the consideration of economy in cost of excavation of the channel. o The drop structures are located in relation to ground level and channel bed level so as to balance cut and fill between reaches as far as possible. o In secondary or tertiary canals, which irrigate surrounding lands, the drop structures are located in such a way that they don’t cause any loss of command. _______________ _______________________________________________________________ Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009 53Erer Dam & Irrigation Project ZCECE & CES o The full supply level in the channel may be so marked that it covers all the command points and allows a minimum working head of 0.15m for off- taking regulators and 0.15m for outlets o The Froude Number (i.e. V/*Vgd) is not allowed to excess 0.5 in approach channel, o The drop structures are designed to have straight drops and standard impact basin, o Dead load of concrete and soil, lateral earth pressures and earthquake forces (not generally significant) are considered to decide component structures. o There are various types of falls constructed in the world such as ogee falls, rapid falls, vertical drop falls, glacis falls, modified glacis type etc. However on extensive research carried out in Poona Research Station of Central Water Commission, Govt, of India un-flumed vertical falls with discharge up to 15 m3/s and fall height up to 1.5m are found most satisfactory. Hence un flumed vertical falls (crest length equal to width of canal) are recommended in the present context. The cost of this type of fall is the lowest. In vertical drop fall the nappe impinges in to water cushion down below and dissipation of energy is affected by the turbulent diffusion. No standing waves are created. The Cistern Length- 5( H * D ) L 05 The Cistern Depth = 0.25 (H ♦ D) L 273 l Where: H = Drop of fall (m ) D = Depth of crest below T.E.L.(m) o In main canals the cistern may be constructed with side and floor thickness of 300mm thick in C.C. C-30. In secondary and tertiary canals drop structures may be constructed with stone masonry laid in 1:4 cement mortars. The inner side of cistern may be plastered with 1:3 cement mortars. A typical drawing of drop structure has been given in Drawing Volume. 9.5 Tertiary canal Head Regulator Tertiary canal head regulator structures shall comprise of a single gated intake followed by a pipe conduit under the canal embankment often opening into a measuring weir outlet structure 54 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES The gates on the head regulator will be simple straight lift gates that can be operated by an individual man. Preferably gates shall be locked, to safeguard against unauthorized operation/tampering. A typical drawing of tertiary canal head regulator has been given in drawing Volume. 9.6 Duck Bill Weir Structure Duck Bill Weirs are very simple structures used as cross regulators in small secondary canals for controlling the water level in upstream of head regulators. Duck Bill Weir is preferred over the straight weir because the level control in the parent channel is affected by minimum afflux. A Duck Bill Weir may or may not be followed by a fall structure depending upon the site conditions In case of small discharges a simple broad crested weir having the same width as that of parent channel followed by a fall will be adequate. A typical drawing has been given in Drawing Volume. 9.7 Tail Escape Structures At the end of every canal, whether secondary or tertiary, a tail escape is provided. This is very simple structure made in masonry or concrete as broad crested weir followed by a masonry cistern whose crest is kept at the full supply level (FSL) of the last reach of the channel. The length of broad crested weir is proposed to be about 2.0 times the width of the end channel at FSL so that effluxes caused by weir are minimized The tail escape channels are provided to join the existing drain falling in their alignment and have been provided to have the same section as that of its parent channel but with reduced bank width. A free board of 0.2ft (=60mm) has been provided above FSL. 55 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES 10.0 Cross Drainage Structures Following types of structures are proposed, depending on the site conditions, size of drains and economy: A total of 33 cross drainage works are proposed on praimary, secondary canal I and secondary canal II. Their location, design discharge and type of structure choosen is tabulated as shown in the table below (table 10.1) Table 10.1 Cross Drainage works No Name Chainage (m) Discharge (m3/s) Type of Structure Proposed 1. CD3-P 3,100.00 0.9 Single pipe 2. CD4-P 3,880.00 2 Single pipe 3. CD9-P 10,660 00 0.75 Single pipe 4. CD10-P 11,040.00 0.9 Single pipe 5. CDI2-P 12,400.00 0.75 Single pipe 6. CD13-P 12,860.00 0.9 Single pipe 7. CD14-P 13,000.00 0.9 Single pipe 8. CD2-S2 2,400.00 2 Single pipe 9. CD2-P 1,720.00 0.84 Double pipe 10. CD15-P 13,180.00 2.4 Double pipe 11. CD3-S2 2,840.00 2.4 Double pipe 12. CD10-S2 9,220.00 2.4 Double pipe 13. CD1-P 420.00 2.8 Triple pipe 14 CD8-P 9,800.00 2.6 Triple pipe 15. CD5-S2 5,220.00 23.8 Slab culvert 16. CD13-S2 10,660.00 38.3 Slab culvert 17. CD6-PZ 5,040.00 2.49 Syphon 18. CD7-P 8,080.00 2.38 Syphon 56 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES 19. CD11-P 11,656.00 2.21 Syphon 20. CD16-P 13,340.00 2 Syphon 21. CD5-P 4,280.00 2.49 Syphon 22. CD1-S2 1,480.00 0.77 Syphon 23. CD4-S2 4,480.00 0.555 Syphon 24. CD6-S2 6,360.00 0.418 Syphon 25. CD7-S2 7,680.00 0.3 Syphon 26. CD8-S2 8,300.00 0.221 Syphon 27. CD9-S2 9,020.00 022 Syphon 28. CD2-S1 2,460.00 0.767 Syphon 29. CD3-S1 2,740.00 0.65 Syphon 30. CD4-S1 3,640.00 0.65 Syphon 31. CD1-S1 860.00 267.5 Aqueduct 32. CD5-S1 6,160.00 92.2 Aqueduct 33. CD11-S2 10,340.00 87 8 Aqueduct 1. Aqueducts 2. Culverts Pipe culverts a. Single pipe culvert b. Double pipe culvert c. Triple pipe culverts Box culverts a. Single box culvert b. Double box culvert c. Triple box culvert 3. Syphones _______________ _________ ______________________________________ 57 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES 10.1 Aqueducts There are three sites where aqueducts have been proposed because the discharge of drains crossing canals are too high where culverts shall be costly in comparison to troughs carried over the drains on piers Two secondary canals one shall be crossing Decho River to extend irrigation on other side of Decho River. Besides, two aqueducts are also proposed for secondary canal-I and secondary canal- II crossing Kebanawa River. Following are the design criteria proposed for design of aqueduct structures. o The choice of type of aqueduct depends up on consideration of economy which in turn will depend on size of drain to be crossed and size of canal. It will also depend on foundation strata at crossing site, dewatering requirements, envisaged head loss and topography of the site. o The design flood for drain crossing a canal depends on size of canal, size of drainage channel and location of cross drainage structure. For choosing appropriate frequency of design flood following table has been referred Canal Discharge Estimated drainage Frequency of Design Flood (cumecs) 0-0.5 0.5-15 discharge (cumecs) All discharges 0-150 1 in 25 year 1 in 50 year 58 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES On this basis the design flood of 1 in 50 years is recommended and the design has been done for this frequency of flood. In plain the channels are in alluvium and water way provided is 60 to 80 % of water way calculated by Lacey’s formula as below: p w = Q q 1/2 Where: P = Wetted perimeter in m w C = Coefficient whose value is normally 4.83 3 Q = Design discharge in m /sec This is the distance between two abutments. However in this design the water way has been taken almost equal to Lacey’s width and no contractions are assumed o In the present option the earth banks are discontinued over the drain and canal water is carried in a rectangular RCC trough. The sides of canal are connected in either side of aqueduct to the earthen banks preferably by means of transition walls. Canal is generally flumed to effect economy. But in this design no fluming is assumed because the sizes of canals are very small. o The layout of the aqueduct is so fixed that it is in straight reach of drainage channel. The canal crosses the drain at right angle o The transition in canal has been provided with 1:2 splay in upstream and 1:3 in down stream sides respectively. It will ensure that the flow to follow transition boundaries, o In case of canal trough supported on piers, expansion joint of sufficient width have been provided at the centre of pier. In Erer project the Primary canal and secondary canal-II are designed as contour canals, therefore, no drop structures are required on these canals. However in case of secondary canal-I it descends about 48 feet in about 1.0 km length before it crosses Dencho river a series of drop structures shall be required to negotiate this descent. Considering the above points a number of drop structures of 59 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES 1.50 m fall are recommended These drop structures will have 5.54 m length of cistern and 0.30 m depth of water cushion. Rest of the details are indicated on the drawing. Depending upon the canal passing over the drainage channel, an aqueduct may be classified in three categories Type I is one where canal continues over the drainage channel in its normal earthen section including the banks and earthen slopes. In this case the length of culvert through which drainage water is passed should have sufficient size to accommodate the canal and its banks. Type II is one in which canal continues in its earthen slopes and outer slopes of banks are replaced by the retaining walls which shorten the length of culvert. Type III is one where earthen banks are discontinued over the drainage channel and canal water is carried through the masonry or concrete trough, box barrel or pipe. The sides of the trough are connected on either to earthen banks of canal by means of transition walls Generally the canals are flumed to affect economy In large rivers aqueducts of type III are adopted because it ensures overall economy This type of structure is recommended in providing drainage crossing for secondary canal-I and secondary canal-II over Dencho River whose discharge is of the order of 270 0m3/sec The discharges of secondary canals are low (varying between 0.7 to 0.9m3/s) in comparison to flood discharge of Dencho river. Troughs of an adequate size are adopted and a free board of 0.3m is considered adequate. The trough is proposed to be of reinforced cement concrete proposed to be designed as beam. This is carried over a no of piers and side abutments made of stone masonry laid in 1:4 cement mortar. The joint have been provided in centre of pier across the trough to accommodate the movement in either direction At every joint a gap of 15mm is provided and water stops (PVC seal) are also embedded to protect water loss through the joint. The recommended width of pier for the span of 5 to 6m is of the order of 0.S5m. Hence 1.0m width is adopted for the span of 10m. On the top of pier a bed block of 0.2m thickness is provided The pier is proposed to have semi-circular nose and cut water radius of 0.5m.The thickness of the pier is proposed to be increased from 1.0 m to 1.6 m in two steps below the scour level. The piers are based on the foundation concrete of appropriate size located at level which is equal to the depth of anticipated scour around the pier plus 1.0m as a grip length 60 Annex E : Irrigation & Drainage Design /Final Detail Design Report /20093 3 3 Erer Dam & Irrigation Project ZCECE & CES The minimum width of abutment at scour level is kept 0.6 times of the scour depth below FSL. The abutments are designed to stand earth pressure coming from its back side created by dry and submerged soil. The width of abutments is increased from 570 mm at the top to 1100 mm at the bottom i.e. above the level of foundation concrete. Foundation concrete of 1800 mm wide and 600 thick is proposed to be provided below the abutments. 10.2 Culverts There are eighteen small drains crossing primary canal. Their 25-year return period discharges vary from 0.75 to5.9 m /s. For the drains carrying discharge up to 1.57 m /s, a single pipe culvert is provided. For discharge lying in between 1.57 to 3.04 m3/s twin pipe culverts are provided. Similarly triple pipe culverts are provided for discharge varying from 3.04 to 6.4 m /s (with 0.5m submergence) There are five cross drainage structures proposed on secondary canal-I. Out of these there are two aqueducts as mentioned under “aqueducts” above. Of the remaining three are siphon. Similarly thirteen natural drains cross secondary canal-II. One is designed as aqueduct being a major drain crossing One is designed as single pipe culvert, two as twin pipe culverts, two as slab culverts and remaining are siphon. In every system, canals cross some natural drains along its alignment. Provisions are required to be made to cross the drain across the canal safely without damaging the canal structure and interfering with its functions. The cross drainage works may be three types depending upon the level at which a drain crosses the canal. If the level of canal bed is higher than the full supply level of drain the drain is designed to cross through an aqueduct or siphon aqueduct or culvert. If the situation is other way round, the 61 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES drain will cross through super passage or siphon. In a special situation when water level in drain and canal is approximately the same the structure in this category will be level crossing The cross drainage culverts have been designed to have sufficient size to pass 25-year return period flood The catchments area of these drains have been demarcated on topographical sheets in 1:50,000 scale. US SCS method has been used for determining 25-year and 100-year return period flood discharges The IDF- curves which have been developed from data of self recording rain gauges situated in the region and surrounding area have been used for finding out the peak discharges. The natural drains which cross the canals shall have adequate cross section to pass flood discharge of 10-year return period. If the existing section is smaller than the one required for passing 10-year return period flood the drain section has been recommended for resection to the desired size. Following design criteria have been used for various components associated with cross drainage structures: (a) Joints-Joints have been provided along and across the drainage barrel length at a spacing not exceeding 20m in either direction. A gap of 15mm has been provided at each of joint and water seals (made of rubber or synthetic material) are provided across all these joints. (b) Collar -In case of barrels resting on compressible soils collars encircling the joints have been provided. This will protect water stops from shearing due to differential settlement Cross section of collar has been assumed not be less than 300mmx300mm. (c) Free board. A free board of 300 mm has been provided in trough of the canal as the discharge of canal is less then 3.0 cumecs. However the free board provided in the drain is as below: 62 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES Discharge of drain (cumecs) Up to 30 30-100 100-300 Free board (mm) 400 500 600 (d)Allowable velocity: Maximum velocity in case of concrete and stone surface is not allowed to increase beyond 4 m/s. (e) Inlet submergence : In case of siphon and siphon aqueducts the submergence has been decided on the basis of topographical considerations. (f) Minimum pipe cover; A minimum cover of 600mm has been provided. 10.3 Inverted Siphons Siphons are proposed when the high flood level of the natural drain is higher than the bed level of the crossing channel. The structure mainly consists of inlet transition, circular barrel and outlet transition. Out of the total cross drainage works 5, 3 and 6 siphons are proposed on primary, secondary canal 1 and secondary canal 2 respectively. Detail hydraulic design is shown in ANNEXE (calculation of irrigation structures). 63 Annex E ; Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES 11.0 Field Drainage System In genera) the drainage system comprises of field drains, tertiary drains, secondary drains and main drains The excess water from the land is gathered by a network of field drains. The excess water which ponds on the surface, flows laterally in the form of overland flow and enters the field drains. The field drains discharge into tertiary drains which finally carry water to secondary or main drain. The field drains are aligned along the field boundaries. The surface drainage system is most effective in case of soils which are impermeable (vertisols or black cotton soils) or in special situation when vertical flow of infiltrated water is impeded by presence of impermeable layer. There is total 40 number of field drains planned in entire command area. These comprise of 13 field drains. The list is given in three tables as given below. These drains are aligned along the depression lines so that the fields may directly discharge in them under gravity. The lengths of majority of these drains are within the range of 1000 to 1500 m. However there are few drains which are above 2000m long. These drains directly drain into existing drainage system in the area. This has happened because the canals are proposed to irrigate their commands comprising of strips of lands situated on their left sides in widths varying from 500 m to 2000 m. On account of this special layout the need for tertiary drains has minimised. There are only two tertiary drains proposed in the whole of command area. The field drains are designed to evacuate superfluous rain and irrigation water from the command area in 24 hours as the dominant crops are maize and cotton which can stand flooding of 24 hours. In a situation when any field is being irrigated and heavy rain occurs, the field drainage system should be capable of removing excess rain and irrigation water effectively during stipulated time otherwise it will result in impairment of crop growth and farm operations. 64 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES Table 11.1 Details of Field drains of Main canal Erer project Field drainage of the main canal Name Area Length Location Drain (ha) (m) (chainage) to FD1P 15 300 1+350 Erer River FD2P 30 700 1+950 Erer River FD3P 35 1400 3+150 Erer River FD4P 60 1000 3+700 Erer River FD5P 35 500 4+250 Erer River FD6P 50 1500 4+800 Erer River FD7P 35 900 5+800 Erer River FD8P 50 1400 6+600 Erer River FD9P 55 1100 7+450 Erer River FD10P 45 1200 9+000 Erer River FD11P 40 1400 9+400 Erer River FD12P 40 900 10+400 Erer Riyer FD13P 35 800 11+300 Erer River FD14P 50 1400 12+600 Erer River FD15P 30 1400 13+300 Decho River FD16P 70 1700 •0+050 Erer River FD17P 50 1700 *0+500 Erer River FD18P 40 1600 *1+000 Erer River ‘chainage started from secondary canal Table 11.2 Drains of Secondary canal-1 Name Area Length Location Drain (ha) (m) ( chainage) to FD1S1 50 1700 2+000 Dencho River FD2S1 30 1400 2+700 Natural Drain FD3S1 35 1400 3+200 T1DS1 FD4S1 30 1300 4+200 T1DS1 FD5S1 60 1900 4+800 T1DS1 FD6S1 55 1400 3+000 Erer River FD7S1 50 1300 3+400 Erer River FD8S1 40 1200 3+900 Erer River FD9S1 20 1000 3+700 Erer River FD10S1 25 1000 3+900 Erer River Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES FD11S1 50 1000 5+200 Kebenaw River FD12S1 30 900 5+700 Kebenaw River FD13S1 65 1600 6+000 Kebenaw River FD14S1 70 2700 6+800 Erer River FD15S1 80 1600 7+300 Erer River FD16S1 50 2600 8+300 Erer River Table 11.3 Drains of Secondary Canal- II Name Area Length Location Drain (ha) (m) (chainage) to FD1S2 40 800 0+000 Dencho River FD2S2 30 800 0+600 Dencho River FD3S2 20 600 1+200 Dencho River FD4S2 60 1700 3+200 Natural Drain FD5S2 45 2500 3+600 Natural Drain FD6S2 90 1800 6+800 Natural Drain FD7S2 90 1300 6+800 Decho River FD8S2 90 1800 8+100 Ija Oda River FD9S2 50 1300 10+200 Natural Drain FD10S2 60 1000 11+000 Kebenaw River FD11S2 30 900 11+400 Kebenaw River 11.1 Excess Rain Water Surplus rain water is found out by US SCS method. The surplus rain water depends mainly upon type of soil, vegetative cover, land use and rainfall. 2 Q = (P-0.2 S ) /( P + 0.8 S ) Where Q= Surplus Rain in mm P= Rainfall in mm S=Retention Parameter in mm derived from SCS Curve Number. Assuming the condition of moderate runoff potential CN = 76, S = 80.2, precipitation depth in 24 hr of return period 5 years is equal to 60.0 mm. (refer Hydrology report, IDF curves are reproduced below) This is found by converting the available IDF curves on semi-log paper 66 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES because interpolation of 24-hr rainfall of 5-ycar return period is not possible from the available plot being on mathematical scale. Intensity-Du ration-Frequency Regions A1 & A4 Figure 6-9 Duration, min. 2 2 Q= ( P-0.2 S ) / (P + 0.8 S ) Q = ( 60 - 0.2* 80.2 ) / ( 60 + 0.8*80.2 ) = 15.41 mm in 24 hr = 15,41 *1000* 104 1000*24*3600 = 1 78 1/s/ha 67 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES 11.2 Excess Irrigation Water At the time when a field is receiving irrigation, heavy rainfall may be experienced at the same time. In this situation field drainage system should be in position to evacuate the total surplus water caused by rainfall and irrigation, both. It is assumed as 70% of field water supplied for irrigation per ha during the months of maximum demand be evacuated along with surplus rain water. The field water supply in October is of the order 0.60 1/sec/ha. The 70% of this works out to 0.42 1/sec/ha. 11.3 Field Drain Capacity Total surplus rain and irrigation water works out to 1.78 + 0 6 * 0.7 = 2.2 1/s/ha Drainage requirement of 60ha field will work out to 60 * 2.2 1/s = 132 1/sec The field drains shall be designed to evacuate 1321t/sec (0 132m /sec) excess water As mentioned in design criteria, the field drains are proposed to be aligned along drainage lines at the existing slopes. These are proposed of triangular section with side slopes of 6:1. There is no need of providing of any free board. The field drains shall be designed with Q = 132 1/s (0.132m /s), N = 0 030, Side slope 6:1, Triangular section and Manning’s N = 0.030 if maintained well and free from vegetation and 0.035 otherwise Table 11.4 Permissible Bed slopes for different sizes of field drains ( N=0.03 ) 3 3 Area of field (ha) Drain discharge (m3/s) Side slope H:V Depth of flow (m) Bed slope (%) Velocity (m/s) 30 0.066 6:1 0.13 1.8 0.70 40 0.088 6:1 0.15 1.36 0.69 50 0.110 6:1 0.16 1.28 0.72 60 0.132 6:1 0.18 1.2 0.68 80 0.176 6:1 0.20 1.0 0.73 68 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES In the table above designs of field drains draining areas from 30 ha to 80 ha are given. The maximum allowable velocity which does not cause erosion is assumed as 0.75 m/s. The limiting bed slopes are worked out by using Manning’s formula. The depths vary from 0.13m to 0.20m for discharges varying from 66 1/s to 176 1/s. As may be revealed from the above table, when the bed slope increases beyond 1.0 % for field channel draining 80 ha area the velocity increases beyond 0.75m/sec (allowable). Drop structures shall be provided at suitable points when available slope increases beyond 1.0 % to control flow velocities and consequent erosion. Similarly for field drain draining 40 ha area the limiting bed slope will be 1.36 % beyond which the velocity will increase beyond permissible limit. Hence for this size of drain the drop structures shall be provided at suitable locations when available bed slope increases beyond 1.36 % to ensure non-erosive flow. 11.4 Tertiary Drains The field drains discharge into tertiary drains. All the tertiary drains shall follow drainage lines or depression ditches from the consideration of economy and shall have drop structures at regular interval to control erosion. Small drop structures at frequent intervals shall be preferred over few large structures because in doing so, the earthwork will be economized. Tertiary drains normally discharge into existing drains or gullies. The sites where the tertiary drains join existing gullies shall be protected to avoid erosion The cross sections of tertiary drain shall be trapezoidal with side slope 3:1 and minimum bed width 1.30m and shall be designed Manning’s formula withN = 0.030. If the existing gradient along the drain alignment is higher than required for maintaining the safe velocity, drop structures having straight fall of 1-2 m height are recommended to be provided at suitable locations. There are only two tertiary drains in the command of Secondary canal -I. In rest of the command, there are no tertiary drains and there are only field drains. The tertiary drains of secondary canal-I are designated as T1DS1 and T2DSl.The length of T1DS1 is 1500m and three field drains namely F3DS1.F4DS1 and F5DS1 join it. The available slope of this drain is about 1.6%. The total area 69 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES drained by these field drains is 155 ha The required size of the tertiary drain will be equal to 0.341 m3/s (155*2.2 =341 1/s ). However T2DS1 is 2600 m long drain which drains 130 ha area In the head reach of about 1600 m length till the area of its drainage is about 80 ha it will be a field drain and have triangular section. In the last reach of 1000m it will be designed as tertiary drain having discharging capacity of 0.286 m3/s (130*2.2=286 1/s). The available slope of this drain is 2.33 %. The design parameters of these drains are indicated below in the table: Table 11.5 Hydraulic Parameters of Tertiary drains Name of drain Discharge (m3/s) Manning’s *N’ Slope (m/m) Depth (m) B.W. (m) H:V V (m/s) Vo =0.55* D064 CVR F.B. (m) T1DS1 0.341 0.03 0.0004 0.42 1.50 3:1 0.31 0.32 0.97 0.3 T2DS1 0.286 0.03 0.0004 0.46 1 40 3:1 0.29 0.31 0.94 0.3 The available slope in T1DS1 is 1.6% and as that of T2DS1 is 2.33 %. These are more than the required slope of 0.04%. Therefore drop structures of 1.0 m fall shall be required to be constructed after every 83 m distance in case of T1DS1 and 52 m in case of T2DS1 respectively. 11.5 Drain Layout The command area which is proposed to be irrigated by Primary canal is to drain directly in to Erer river as the Erer river flows at about 1.0 km from the other end of irrigated area and all the field drains are designed to out fall in this river . The command area of Secondary canal-I is proposed to drain in to Dencho river,Kebenew River, Erer River and partly to a natural drain. The layout of field drains and tertiary drains (only two in number) is indicated on the layout plan of this command included in Drawing Volume. 70 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009f I Erer Dam & Irrigation Project /CECE & CES Similarly the entire command area of Secondary canal -II is drained by Dencho River, Kebenew River and few small natural drains. The proposed drains of this area are designed to drain in these existing rivers/drains. 71 Annex n : irrigation oc drainage Design /rinai Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES____________ . . ------------------------------------------- • * 12.0 Flood Protection Embankments The proposed irrigated area is situated in the right side of Erer River. Primary canal and secondary canal-I extend irrigation to the area located just adjacent to the river course. In some reaches the area is prone to inundation and consequent damage to agriculture To safe guard this area from flooding suitable flood protection works have been designed as per practices in vogue in different parts of the world. To start with the contour plan of the area has been deeply studied and area prone to inundation has been demarcated. No flood protection works already exist in the area. To decide on the important aspects like degree of protection to be provided and alignment and spacing of embankments following studies have been conducted: 1. River characteristics, whether aggrading/ degrading, braided/ meandering, alluvial/incised Silt carrying capacity, Nature of bank and bed materials, Active food plains of the river etc. 2. Hydrological data, recorded discharge data, length and reliability of data, recorded flood levels and highest historical floods, rain fall data. 3. L-section and X-section of the river, safe carrying capacity On having studied the above the following design criteria has been short listed and adopted in design of embankments: 12.1 Design Criteria • The flood protection embankment shall safely contain routed 100-year return period flood (routed through Erer dam reservoir) without spilling to the adjacent agriculture lands. • The spacing between flood protection embankments planned on both banks shall not be less than three times the Lacey’s wetted perimeter. If the embankment is planned on one side of river, which is the present case, the distance between embankment and centre line of river shall not be less than 1.5 times the Lacey’s perimeter. The size of Erer River is small therefore the spacing between protection bank is reduced to two times of Lacey’s perimeter Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009 72Erer Dam & Irrigation Project /CECE & CES • The embankment alignment shall be located on the ridge of natural bank where land is high and both the ends of embankment shall be natural high ground or existing road embankments. • Homogeneous embankment shall be adopted for the reasons of simplicity. • For surface protection of embankment from rains or wind 0.3 m thick turfing shall be provided. • Since the velocities in the close vicinity of embankment will be low, therefore no protection is provided. • The minimum top width of embankment shall not be less than 5.0 m. However in case of Erer river which is small in size, top width of 3.0m is considered adequate. • The side slopes of upstream and downstream side of embankment shall be steeper than 2:1 slope. • The HG line shall have slope of 1:4 to 1:6 for different types of soils of varying texture. Considering the embankment material of medium texture a slope of 1:5 is adopted in designs. A minimum cover of 0.6 m shall be kept over HG line by adjusting the downstream slope. • Borrow areas shall be located on the river side only. For low embankments (height<6.0m ) the borrow areas shall not be selected within 25m of the toe/heel of embankments Besides above design criteria following aspects are recommended for adoption at the time of construction: 1. Soil investigations be carried out to identify and locate the borrow areas. 2 Maximum depth of borrow pits shall be limited to 1.0 m to preclude the chances of disturbing regime of river 3. In order to obviate chances of developing flow parallel to banks cross bars of the width 8-times of depth of borrow pit shall be spaced minimum 60 to 80m centre to centre 4 Settlement allowance of 1 to 2 % shall be made in the height of embankments. 5. All borrow areas shall be stripped of top soil a minimum of 30 cm and all objectionable materials shall be removed. 73 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES 12.2 Design of Embankments The flood protection embankments are designed for containing routed flood oflOOyr return period. The routed flood hydrograph is coursed through the existing river sections and levels corresponding to routed flood are worked out. If the bank full capacity at the existing sections is found adequate no embankments are provided. In the reaches where bank full capacity is found inadequate flood protection embankments are provided with proper free board Flood peak of 100 return periods in upstream of dam site is estimated as 366 6m3/s. The hydrograph of this peak is routed through reservoir and attenuated flood peak comes as 250.5 m3/s Lacey’s perimeter (P= 4.83* Q0 5) corresponding to Q= 250.5 m3/s, worked out to 76 m. If the flood protection embankments are required to be provided they should have minimum 150 m spacing to ensure a stable regime in the river. The entire course of river has been checked for discharge carrying capacity of this order and reaches having inadequate capacity are identified. These reaches are given as below: (a) Pocket-I This is about 55 ha area situated in the proposed command of primary canal. It is located in 1500 m long reach of river extending from 1025500 Northing to 1023000 Northing This area is practically at the bed level of river. The river course is proposed to be jacketed between two flood protection embankments spaced at 150 m apart If routed flood of 250.5 m3/s is coursed through the depth of flood water will rise to about 1.2 m( slope of the river in this reach is 1/300 and Manning’s n is assumed as 0.04, average velocity will work out as 1.6 m/s ) . Hence river protection embankment of 1.7 m height ( 1.2m+ 0.5m for free board ) is proposed along the river in the aforesaid reach running parallel to river course at 75 m distance away from the centre line of the river. (b) Pdcket-11- This is an area of about 12 ha This is also part of the command of primary canal This is situated in the downstream side of Harar -Jijga road crossing of Erer river between ■1022200 Northing to 1021000 Northing. This area is also having the same level as that of river ______________________________________ ____ __________________ __________ Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009 74Erer Dam & Irrigation Project ZCECE & CES bed. Second flood protection embankment is proposed to protect this area. This embankment of 600 m length is proposed to be constructed parallel to existing river course and have the same dimensions and location with respect to river as proposed for pocket-I. Considering above criteria the section of embankment has been designed and the drawing has been given in Drawing Volume. 75 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES 13.0 Construction Materials 13.1 Earth Works The excavated earth materials available from the canal and drain construction shall be suitably used in construction of adjacent roads and embankments. If possible, surplus earth available during construction of canals and drains shall also be used as backfill of structures. 13.2 Masonry and Concrete Works There is very small requirement of stones and aggregates for masonry and concrete to be used in irrigation structures. These materials are locally available as investigated in connection with the requirement of aggregates in dam and appurtenant works. The same investigated quarries may be used to avail these materials. Suitable local stones may be utilized for concrete construction works. Portland cement as available locally may be utilized. The river sand which is in plenty shall be used in masonry and concrete works. The construction materials pertaining to the concrete works shall conform to the relevant BS codes. 76 Annex E Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES 14.0 Operation and Maintenance of Irrigation System The success and failure of any irrigation system depends upon its proper operation and maintenance. If the operation and maintenance of any system is poor, it will not be able to serve its objective function. The canal system should supply the entire requirement of water of the crops in the command area; at the appropriate time so that crops may grow to their full maturity and yield good production without wasting any water. Similarly the drainage system should he operated and maintained in such away that excess water (rain water and irrigation water) may he drained with promptitude without causing any damage to the crops on account water logging. These duties are to be handled by the agencies responsible for the operation and maintenance of the system. As per system existing in Ethiopia there will be two agencies who will be involved in these duties. These are government agency and beneficiary agency. The government of Ethiopia through Ministry of Water Resource can form a special Erer Project Authority (EPA) or Erer Project Control Centre (EPCC) to operate and maintain this system on behalf of the government. However, the beneficiary committee can handle its responsibilities on behalf of all the farmers benefiting from irrigation system The responsibilities among these agencies are proposed to the apportioned in the following manner 14.1 Dam Structure All dam structures including main dam, spill way and outlet structures shall the operated and maintained by the government agency and no other agency is recommended to be involved. 14.2 Regulatory Structures This responsibility is proposed to be divided between two parties as below, i) As the proposed government agency EPA I EPCC shall own all the dam, canal and drainage structures, therefore this agency shall be responsible for maintenance and upkeep 77 Annex E Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES of all the structures built at the expense of the govt. Also, the operation of all regulatory structures up to tertiary canal and tertiary drain level shall vest in this govt agency only. ii) The operation of canal and drainage system below the quaternary canal and field drains shall vest in the beneficiary agency. 14.3 Operation Of Reservoir And Conyeyance System : The operation of reservoir and conveyance system requires special responsibilities during dry season because in the event of scarcities it is challenging task to optimise the benefits from available water. In rainy season, however, the availability position is good and demand is low and therefore it is easier to run the system without facing the scarcities. For skilful management of scarce water resource during the dry season it is proposed that at the beginning of dry season the EPA/EPCC should find out the total amount of water stored in the reservoir and estimate the likely available water during dry season on the basis of dependable flows. The total availability of water during dry season i.e. the sum of stored water in reservoir and quantity of dependable flows shall be communicated to the beneficiary agencies who will decide their weekly demands in view of availability of these supplies in dry season. This will help them to appreciate the handicaps of the system and avoid unnecessary misunderstanding. Regular interaction between EPA/EPCC and beneficiary agencies shall help them to decide schedule of releases with their mutual consent so that the available supplies may be fruitfully used. Thus the operation of reservoir and conveyance system is recommended to be done exclusively by EPA/EPCC as per demand of beneficiaries and availability of supplies 14.4 Field Irrigation The operation of field irrigation system shall be solely handled by farmers who will divert the supplies from quaternary canals in to their field channels and furrow by creating check bunds or 78 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES using flexible pipes. Schedules shall be drawn up for amounts of water required for each unit and furrow and time of flow during each watering. 14.5 Maintenance 14.5.1 Canal Network There are two type of maintenance required in canal system i.e. repair of rain cuts and breaches caused by overtopping of banks and removal of silt and weeds. Both of these type of maintenance are seasonal and periodical. These are recommended to be undertaken by regular gangs of labourers to be controlled and supervised by govt, agency. 14.5.2 Field System All field channels need to be repaired every now and then. It is recommended that this type of maintenance may be undertaken by irrigators themselves either individually or jointly by all farmers availing water from that field channel. 14.5.3 Drains Drains need only seasonal maintenance when their cross sections are blocked by accumulation of debris or weed growth. This is recommended to be undertaken by govt agency by employing labourers seasonally. i 14.5.4 Roads The proposed roads are gravel roads which require maintenance in form of grading regularly and continuously. This is proposed to be undertaken by a gang of labourers specially employed for the job. 79 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES 15. Land Grading Land grading is the reshaping of the surface to ensure even application of irrigation water and quick disposal of the excess surface water for proper growth of the crops. Plane method type of land levelling has been used for this project for its simplicity. The area of the sample block for which land levelling has conducted is 88 ha that has been divided in to four blocks. The first block is divided into 200m wide & 150m wide sub-blocks. The 2nd block is divided into two 200m wide sub-blocks. Each sub-block is divided into units having 50m length and either 200m or 150m width. Grid points of the blocks and their units are based on letters and numbers on Y axis & X axis respectively. The levelling operation will be undertaken for each fifty meter length along the canal. The slopes of the best fit as calculated for the sample block are 0.9% and 1.6% for cross and along the canal. Since the topography of the land is steepy, the maximum allowable slope for loamy soil 0.4%, has been used for both directions. The maximum cut and fill depth that may reach lm at extreme ends for the block units having 200m width will be reduced by reduction of block unit width to 150 m. Grading has been done in such away that cut volumes exceed fill volume by at least 30% to account for compaction. 80 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES Table 1.0 Cut and fill values for each unit (m) 123 4 5 6 7 8 Q 0.9940 0.9365 0.8400 0.8920 0.8605 0.8700 0.6775 0.6120 Q P 0.5740 0.5365 0.4400 0.4120 0.4205 0.4000 0.2875 0.2620 p O -0.0160 0.0765 0.0100 -0.0080 -0.0495 -0.0900 -0.0825 -0.0780 o N -0.6060 -0.4335 -0.3700 -0.4180 -0.4295 -0.4000 0.5375 -0.4680 N M -0.2386 -0.0939 -0.0641 -0.0943 -0.1101 -0.1428 -0.2081 -0.1990 M L -0.0213 0.2481 0.2419 0.1694 0.1994 0.1644 0.1163 0.1200 L K -0.2513 -0.2594 -0.2081 -0.1406 -0.1406 -0.1256 -0.1237 -0.1300 K J 0.1294 0.0913 0.0809 0.0759 -0.0001 0.0527 0.0426 -0.0010 J 1 0.3400 0.4220 0.3800 0.3325 0.2305 0.1910 0.1690 0.1580 I H -0.0300 0.0020 -0.0100 -0.0275 0.0005 -0.0590 -0.0910 -0.0320 H G -0.4600 -0.3880 -0.3200 -0.2975 -0.2595 -0.2290 -0.1910 -0.1220 G F -0.7400 -0.8180 -0.7400 -0.6375 -0.4995 -0.3590 -0.2410 -0.1720 F E 0.7660 0.8450 0.9410 1.0470 0.9835 0.8360 0.9120 0.8230 E D 0.3360 0.2350 0.5210 0.5770 0.6135 0.6060 0.4920 0.4530 D c 0.1160 -0.1750 -0.0690 0.0170 0.1035 0.1760 0.0520 -0.0070 C B -0.0340 -0.6050 -0.7090 -0.5430 -0.5065 -0.4040 -0.3880 -0.3870 B A -0.1640 -0.7250 -1.0690 -1.1530 -1.0965 -0.9740 -0.8280 -0.8270 A 1 2 3 4 5 6 7 8 Cut 3.2554 3.3929 -3.4978 3.4548 -3.5592 3.5228 Fill"-" -2.5611 -3.3194 3.4119 -3.0918 3.296063 -2.7834 3.2864 -2.1534 2.4280 -2.4230 Table 2.0 Cut and fill values for each unit (m) 9 10 11 12 13 14 15 16 Q 0.7130 0.7675 0.8055 0.8130 0.7355 1.6100 0.6945 0.6860 Q P 0.3430 0.3675 0.4055 0.3730 0.3455 1.2300 0.3245 0.3360 P O -0.0170 0.0075 0.0455 -0.0570 -0.0445 0.8500 -0.0355 -0.0240 O N -0.3670 -0.3525 -0.3445 -0.3870 -0.3645 0.5400 -0.3255 -0.3240 N M -0.1610 -0.2238 0.0865 -0.1679 -0.1151 0.3444 -0.0693 -0.0795 M L 0.1150 0.1825 0.1138 0.0813 0.1144 0.1988 0.1569 0.1450 L K -0.1250 -0.1075 -0.1063 -0.1687 -0.1456 -0.4613 -0.1531 -0.1650 K J -0.0347 0.0373 0.0749 0.0176 0.0487 -0.0194 -0.0353 -0.0578 J I 0.1005 0.1320 0.2360 0.1840 0.1330 0.1425 0.1825 0.1595 I H -0.0295 -0.0480 0.0860 0.0640 0.0330 0.0125 0.0225 0.0195 H G -0.0895 -0.0480 -0.1040 -0.1160 -0.1670 -0.1975 -0.1475 -0.1505 G F -0.1795 -0.1980 -0.3140 -0.3660 -0.3670 -0.3675 -0.3575 -0.3505 F E 0.8240 0.6975 0.6315 0.5955 0.5805 0.5615 0.5355 0.4545 E D 0.4440 0.4175 0.3315 0.2955 0.2805 0.2615 0.2355 0.2345 c D 0.0340 0.1875 0.0315 0.0355 0.0505 0.0315 0.0055 0.1045 c B -0.3760 -0.2125 -0.2685 -0.3045 -0.3195 -0.2785 -0.2545 -0.1955 B A -0.7760 -0.6325 -0.6385 -0.6045 -0.6095 -0.5785 -0.5345 -0.4455 A 9 10 11 12 13 14 15 16 ______________________________________________________________________ 81 *3 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES Cut "+" 2.5735 2.7967 2.8481 2.4594 2.3216 5.782625 2.1574 2.1395 Fill"-" -2.1553 -1.8228 -1.7758 -2.1716 -2.1327 -1.9026 -1.9128 -1.7923 Table 3.0 Cut and fill values for each unit (m) 17 18 19 20 21 22 23 Q 0.7410 0.7595 0.4550 0.0225 -0.0760 0.2120 0.1250 Q P 0.3410 0.4395 0.2250 0.2475 -0.1060 0.0220 -0.4050 P O 0.0410 0.1195 0.1250 0.2575 -0.0960 -0.1080 -0.5450 O N 0.2890 -0.2005 -0.0950 0.2775 -0.0860 -0.0880 -0.5550 N M 0.0517 0.0151 0.0428 0.2525 -0.0427 -0.0565 -0.5013 M L 0.1656 0.2106 0.1306 0.1575 -0.0394 -0.0350 -0.4175 L K 0.1444 -0.0394 -0.0494 0.1275 0.0306 0.0650 -0.3575 K J 0.0459 0.0783 0.0048 0.0725 0.1796 0.1312 -0.2928 J 1 0.1525 0.1860 0.2390 0.2425 0.1885 0.1375 -0.2480 I H 0.0075 -0.0040 0.0390 0.1475 0.0485 0.0175 -0.3880 H G 0.1675 -0.2440 -0.1710 0.0875 -0.1715 -0.1525 -0.5080 G F 0.3775 -0 4040 -0.3310 0.2475 -0.3115 -0.3325 -0.6080 F E 0.0320 0.8280 04125 0.3790 0.2060 0.0290 -0.3330 E D 0.2220 0.6080 0.2025 0.1890 0.0460 -0.0710 -0.3130 D C 0.4520 0.4080 -0.0275 0.0410 -0.1040 -0.0810 -0.2630 c B 0.6320 0.1680 -0 2375 0.2310 -0.1740 -0.0210 -0.1830 B A 0.8820 0.0080 -0.3975 0.2610 -0.1940 -0.0210 -0.1330 A 17 18 19 20 21 22 23 Cut"+" 1.4411 3.8285 1.8763 0.9055 0.699187 0.61425 0.125 Fill"-" 3.3035 -0.89188 -1.30888 2.3355 -1.40106 -0.9665 -6.051 Summary: Depth wise: Total cut needed (sum of the “+”) = 58.62 m Total fill needed (sum of the = 51.21 m Volume wise: ________________________________________________________________________ 82 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES Area of each unit = '/< ha = 2500 m2 Total cut needed = 58.62 x 2500 = 146,550 m3 Total fill needed = 51.21 x 2500 = 128,025 m3 Total unit = 23 x 17 = 391 (each unit is '/* of a ha) Using the four point method, the volume of cost and fill is approximated as follows; (E^)1 e £f)' 4 + Vc,Vf = volume of cut, fill L = grid spacing , m ^2 C - sum of cut on four comers of a grid unit V f ~ sum of fill on four comers of a grid unit Thus, the volume of fill = 996,395m3 The volume of cut = 1,41 l,556m3 Covering on area of 3370 of on average depth of cut and fill to be 7cm respectively 83 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009IErer Dam & Irrigation Project ZCECE & CES 16. Bill of Quantities, Cost Estimates and Tentative Construction Schedule 16.1 Dam Appurtenance Works The quantities of the various items of works related to the Erer irrigation infrastructure have been defined with reasonable accuracy compatible with the present knowledge of the technical aspects of the project. The prices adopted for this report are current prices (December 2008) that are based on experience gained from similar projects being undertaken in the country. The bill of quantities and cost estimate shall be used for the purpose of project worth analysis and to have an estimate of the project investment. The tentative construction period is estimated to be 24 calendar months as shown in the annexure. The bill of quantitities and specification is included in volume IV section 2 of the detailed design report. Annex E : Irrigation & Drainage Design /Draft Detail Design Report /2009 85I. AQUEDUCT FOR SECONDARY CANAL -I ON DENCHO RIVER DESIGN DATA (1) Canal Trapezoidal Earthen section Discharge = 0.968 m /sec Depth of water= 0.82 m Bed width = 1.20m Velocity = 0.49 m/s Free Board = 0.30m 3 3 Manning’s coefficient (n) = 0.025 Slope = 0.00040 Side slope = 1.5:1 (2) River Flood discharge (Tr= lOOyr) = 274.0 m /sec High flood level (HFL) = ? River bed level = 1315.8m (3) Type of Structure Proposed The earthen banks are discontinued and the canal is taken in rectangular trough supported on piers. This is adapted to effect over all economy. (4) Drainage Waterway Lacy’s Regime perimeter =4.83 Jq = 4 83 V274 = 79.95 say 80m 1Let clear span between the piers is 6.0m and there are 11 spans and ten piers. Total water way between abutments = 66+10x1.0 = 76m (5) Canal Waterway For reasons of economy, the trapezoidal section of earthen canal is reduced to rectangular section. The clear width of trough = 1.15m, the same as width at Earthen canal Flour area of trapezoidal section = 1.15x0.82 + 0.82 x 1.23 = 0.943 + 1.0 = 1.94 m2 Provide 1:2 splay in contradiction and 1:3 in expansion Fig 1. Canal Waterway-ns (6) Head Loss and Bed Levels at Different Sections Velocity at section 1-1 = 0.49 m/s Velocity at section 2-2 = 0.968/0.943 = 1.03 m/s = 0.0082m Head loss in expansion = 0.3 = 0.3 1.032-0.492^ k 2x9.81 J = 0.012m Head loss in rectangular channel using manning formula (assume n= 0.015 for concrete surface) i1 V= -R2S2 n V= 03 m/sec r= A - 0 943 P ~ 1.15x2x0.82 = 0943 2.79 = 0.33 1.03 = 1 2 I 0.015 (0.33) S2 3 3= 103x0 _ 012 _ 0.00095 0.475 Head loss in the rectangular trough = 00045 x 76 = 0.072m Secondary canal crosses river Decho at chainage 0 + 850 after passing through a series of falls. The FSL in secondary, canal at its crossing point is 1320.00. This is the level which can command the proposed command area of secondary canal Elevation of total energy line = 1320.00 + velocity head 0.492 = 1320.0 +---------- 2x9.81 = 1320.0 + 0.013 = 1320.013 Bed level of cannel at section 1-1 = 1319.18 Head loss in contraction = 0 008 Head loss in expansion = 0.012 Head loss in trough Total = 0,072 = 0.092 Elevation of total energy line at 4-4 = 1320.013 -0.092 = 1319.92m Bed level at section 4-4 = 1319.92 - 0.82 = 1319.12 As may be revealed from the above the loss of head in contraction, expansion, and trough portion is negligible. Therefore the bed level of canal in the beginning of trough is the same as in the end. 4The size of trough will be = 1.15 xl.12 (assuming free board = 0.3m) These are inner dimensions. However the outer dimensions shall be 1.75 xl.12 assuming 0.3m as thickness of trough wall. (7) Piers and Abutments Piers and abutments are proposed to be constructed in stone masonnary laid in 1:4 cement mortar. The recommended thickness of pier for span 5 to 6 m is 0.85m. Hence 1,0m in thickness is adopted. The pier width shall be increased to 1.6m in two steps. Foundation concrete l.Om thickness shall be provided below the pier. Thus the foundation concrete shall comprise of 2.2m wide and 1.0m thick base. On the top of pier a cement concrete bed block of 0.2m thickness shall be provided which will be projecting to 0.15m outside on all directions. The pier shall have semi circular nose and cut water radius of 0.5m. The width of abutment at scour level should be approximately 0.6 times the scour depth below FSL The abutments shall stand the earth pressure of dry soil above the pressure gradient line and submerged soil below the line. The width of abutment shall increase in steps standing from 570mm at the top to 1100mm at the bottom i.e above the level of foundation concrete of 600mm thickness. The foundation concrete 1800 x600mm shall be provided below the abutment (8) Depth of Foundation Normal depth of scour according to Lacy’s equation is R= 0.47 l/J f = 1.5 assumed for river bed material 5Anticipated depth of scour around pier = 2R = 2x2.62 = 5.24m The minimum depth of foundation below anticipated scour level should be less than 1.0m or 1/3 of scour depth. Hence, depth of foundation below FSL = 5.24 +1.0 = 6.24m The level of foundation concrete will be HFL in rever = 6.25m = 1317-625 = 1311.75m B Fig 2. Aqueducts on Secondary Canal I 6I i l I I I 1 I I I i SfecfimCC fl fl fl fl fl fl fl .. I I u I15 Section C - C Note: All dimensions are in mm 8n. DESIGN OF AQUEDUCTS ON SECONDARY CANAL I AND D There are two aqueducts on secondary canal - I and one remaining aqueduct on secondary canal - II. In design of these aqueducts the same procedure is followed as in the case of aqueduct designed on Decho River. 1. Name of Aqueduct Kebanawa on S2 Abiyo on Si Kebanawa on Si Remarks 2. Chainage of x-ing points (km) 10.200 3.30 6.10 3. Data of canals at crossing points J a) Q(m /sec) 0.11 0.66 0.429 b) Depth (m) 0.43 0.69 0.58 c) B .L 0.88 1.15 1.0 d) Velocity 0.33 0.44 0.40 e) Side slopes 1.5:1 1.5:1 1.5:1 f) Slope 0.00045 0.0004 0.0004 4. Flood discharge of drains (m3/s) Return period of 25 years. 87.8 46.1 92.2 5. Lacy’s per meter (m) i P=4.83 Q’ 45.2 32.79 46.37 6. Width off one span (assumed ) (m) 6.0 5.0 6.0 7. No of spans 7 6 7 8 No of piers 6 5 6 9. Thickness of pier (m) assumed 0.85 0.70 0.85 10. Total water way (m) 47 1 33.5 47.10 11. Size of tough (mxm) a) internal dimensions BxD 0.88x0.75 1.15x1.0 1.0x0.88 Assumed: Free board = 0 b) outer dimensions BxD 1.28x0.75 1.15x1.0 1.40x0.88 Thickness of wall = 0.22 12. Bed level of trough Same as the bed level of canals at the beginning of crossing point * 913. Scour depth (m) ‘R’ 1.80 1.66 1.82 z \ * R=0.47|— - F= 1.50 assumed for river bed 14. Anticipated depth around (m) Pier =2R 3.60 3.32 3.64 15. Minimum depth of foundation below FSL (m) = 2R+1.02 4.60 4.30 4.64 16 Maximum depth of flow at the time of flood (assumed) * 1.0 0.7 1.0 17. Minimum depth of foundation below bed level (m) 3.60 3.60 3.64 18. Length of pier with indicated cut water radius(m) Figure3-a Figure3-b Figure3-c 19. Size of form Depth 0.7 0.6 0.8 Width 2.05 1.90 2.05 * Level may be indicated after finalization of L-section of SI & S2 ♦May be get collected if possible ** See the figure below Provide cc bed block of 0.2m thick at the top, projecting 0.15m on all the side Width of abutment at scour level shall be 0.6time the scour depth below FSL The width of abutment shall increase in steps from 570mm at top to 1100mm at the bottom i.e. above the level of foundation concrete of thickness 600mm. The foundation concrete of 1800m x 600m shall be provided below the abutment. The size of abutment will work out the same with case of all the aqueducts. 10*- Fig 3-a Length of pier Fig 3-b Length of pier Fig 3-c Length of pier 11I I ID. SAMPLE DESIGN OF DUCK BILL WEIR I I I Chainage = 13.300km of primary canal Primary canal parameter Bed width = 0.13m Bed level 1359.24 Depth = 1.0m FSL= 1360.24 Velocity = O.55m/s Top bank level = 1360.64 Discharge = 2.0 m3/sec ground level = 1360.08 Side slope = 1.5:1 Slope = 0.00035 I I I Tertiary canal (T.P) parameters Q= 0.154 m3/sec Depth = 0.41 m Bed width = 0.53m F.B = 0.20 m I a Velocity = 0.32 m/s Using broad crested weir formulas 3 I Q= CLH5 C= 1.705 a a Q= discharge of primary canal - discharge of off taking canal Q= 2.0-0.154 Q= 1.846 m3/sec a a a a Fig 4. Water flow over a weir a a 12Length of weir = 1.846 Q - Q 3 3- CH- CH2 2 3 1.705x7/’ Let H= 0.352 1.846 L = 1.705x0.20 = 5 41m say 5.4m 2A+ 1.5 = 6.72 2A = 6.72-1.5 2 A = 5.22 A= 2.61 Cos a = —=0.5747 2.61 a =55° This is acceptable figure which lies between 45° and 70° Cut off wall and floor thickness required: 1 846 3 Discharge intensity over the crest = —------ = 0.21 m /sec 6.72 i Normal scour depth =1.35 — = 0.35m Up stream depth provided = — + 0.6 1.0 ——+ 0.6 = 0.93say lm, Provide 1.0m deep cutoff Down stream cutoff depth = — + 0.6= 1.1m, Provide 1.20m cutoff Maximum static head H= water level up to crest of duck bill weirand no water on down stream side = 0.69m Assuming Bilght coefficient = 7 Total length of floor required = 7x0.69 = 4.83 (provide 5.0m floor length) Provide 2m in the up stream and 3.0m in the d/s of Duck bill weir 0.69 . Total unbalance head just downstream of weir = —x3 = 0.414m The discharge coefficient depends upon shape and angle of crest. The volume of coefficient of discharge up stream rounded crest =0.360 72g =0.360x4.43 =1.59 Using coefficient of discharge as 1.59, the length of weir will increase to 1,846 1.59x0.20 5.80 14The use of Duck bill weir is preferable to the angle ‘ a ’ varying between 45 to 70° The end of duckbill weir crest is fixed independent of the bed width of canal Let it is 1.5m 2A+1.5 = 5.8 A= 58-1.5 = 4.3 A= 2.15m Cost a = — = 0.6976 2.15 a = cos 1 0.6976 a = 45.76° It is the margin case Let the head over crest the reduced to 0.3 Im The thickness required = —----- = 0.33/n 1.24 Provide 400mm thickness in halt length of downstream toe of crest wall and 300mm in rest of the floor as shown below. 1.846 1.846 1.59x(0.31)? L59x0 1726 0 414 = 15A PLAN Fig 5. Typical Drawing of Duck Bill Weir “16rv. DESIGN OF OUTLET STRUCTURE Given: Discharge Length = 40 let/sec = 7.0m Slightly encrusted cast iron pipe f = 0.01 height from centre of outlet to FSL 0.75m Let us choose 15cm diameter pipe q = CA JlgH C = 1 2x10s d V 400/ C = 1 1 15 2x10 | s 0.01(7 + 15X15 ) 400x0.01 C = 1 1 15 2x10 \ 0.01(7 + 5.625) C = 1 1 15 q= 40 lit/sec = 0.04 m3/sec 0.04 = 5.45 x 10'5 x A-79.81x2x0.75 0.04 A 5.45xl0’ x^9.81x2x0.75 s 0.04x10s 4000 A= ------------ =-------------- = 191 63 5.45x3.83 5.45x3.83 s 2x10s (0.01x12.625) C= —L 2x1 rxl0.95 = 5.45X10-5 05 A=------------- =-------------- = 191 63 0.04x10s 4000 ___ 5.45x3.83 5.45x3.83 W2 A=-—= 191.63 4 4x191.63 ----------- 4x191.63 =244.11 7Td 2= 244.11 d = 15.62cm use 15.0cm diameter pipe, for 401it /sec discharge PLAN 18Fig 6. Typical Outlet Structure IV. DESIGN OF CROSS REGULATOR CUM HEAD REGULATOR (a) Primary canal parameters Length of primary canal = 13.394k FSL at of taking point of Dam outlet = 1365.0 Longitudinal slope 35cm per km FSL at tail of primary canal = 1365.0 - 0.35 x 13.394 = 1365.0-4.68 = 1360.31 m Depth = 1.0m Bed level = 1360.31 - 1.0 = 1359.31 Bed width = 2.13m (b) Secondary canal one parameters Head discharge Bed width Water depth - 0.968 m3/sec = 1.20m = 0.82m Assume operating head for secondary canal I as 0.10m FSL of secondary canal = 1360.31 -0.10 = 1360.21m Bed level = 1360.21 - 0.82 = 1359.39 19• . - ♦ ♦ Gate size and operating platform Crest of the secondary canal is kept at the bed level of the primary canal. Gate of 1 40m wide and 0.95m high shall be provided to control the flow in the secondary canal. Level of operating platform will be 2x0.95 + 0.95/2 = 2.375m above the bed of secondary canal The level of operating plat form will be = 1359.39 + 2.375 = 1361.76m from bed level. Operating platform of 2.0m x 150m shall be provided. Floor length When secondary canal I is closed The water level is primary canal will be at FSL = 1360 31 Bed level of secondary canal I = 1359.39 Difrence of head = 1360.31 - 1359.39 = 0.92 Taking blight’s coefficient = 7 Total length of floor = 0.92 x 7 = 6.44m Provide 7.0m floor, 3.5m up stream of gate and 3.5m d/s of this gate Vertical cutoff Minimum depth of up stream and downstream cutoff for discharge < 3.0m3/sec = 1,0m Provide 1.1m deep vertical cutoff on upstream side R.L. of cutoff in upstream side = 1359.31-1.1 I 20= 1358.21m Provide 11m deep vertical cutoff on the downstream side R.L. of cutoff in downstream side = 1359.39-1.1 = 1358.29m Floor thickness Draw hydraulic gradient line at 1:7 for maximum static head of 0.92m that is when water is headed up to FSL on upstream side and no water on dawn stream side. The ordinate between H.G line and floor level would give unbalanced head Provide 0.30m thick floor on the upstream side of gate. 0 92 Maximum unbalanced head =------ = 0 46m 2 Floor thickness required = 1.25 = 0.368 Provide 0.4m thick concrete floor on the downstream of gate. Downstream protection Q 0.968 naA 3, , q= — =------- = 0.84 m/sec/m b 1.15 R= 1.34^’= 1.19m f = 1 For straight reach depth of scour = 1.25R = 1.25x1.19 = 1.49 Depth below bed = 1.49 - 0.77 = 0.72m This is less than the mandatory requirement of 1.Im 21Concrete blocks Downstream of the impervious concrete floor, suitable protection works is the length 2D = 2x1.1 = 2.20 say 2 40m Provide four rows of 600x600x250 cement concrete blocks or stone masonry blocks over 150mm thick well graded stone ballast Launching Apron: Beyond protection work, launching apron shall be provided The cubical content of the material in launching apron will be 2.25D m3/m length Cubic content = 2.25 x 1.1 = 2.464 Keeping the thickness as 600mm The length of apron = 2 46 = 4.125 Provide 4.5m long launching apron Provide 250mm thick 500mm deep wall between block protection and launching aprom (c)Parameters of secondary canal II Discharge at the head = 0.773 m3/sec Bed width 1.15m Waler depth = 0.74m Assuming 0.15m as driving head The FSL in secondary canal -II is = 1360.31 - 0.15 = 1360.16m Bed level in secondary canal II = 1360.17 - 0.79 = 1359.43m Adopt gate size of 1.35m x 0.85 Level of operating platform = 1359.43x2x0.85 + 0 425 = 1359.58 + 1.6 + 0.4 = 1361.96m 22Thickness of operating platform is 150mm Operating platform of 2m x 1 5m shall be adopted When secondary canal -II is closed Floor length Water level in primary canal = 1360.3 lm Bed level in secondary canal = 1359.43m Head = 1360.31 -1359.43 = 0.88m Taking Blights coefficient = 7 Total length of floor required = 0.88 x 7 = 6.16 Say 6.0m Provide 3 m floor length in the upstream and 3 .0m in the down stream of gate Vertical cutoff The minimum depth of upstream and downstream cutoff for this range of discharge will be 1.0m. Provide 1.1m deep cutoff in the upstream side & downstream side The level of upstream cutoff will be = 1359.31 - 1.1 = 1358.21m The level of the downstream cutoff will be 1359.48 - 1.1 = 1358.33 23I I I I I I I I I I I I 1 1 I 1 I I I I Floor thickness ~ -wi—JDraw hydraulic gradient line at 1:7 for the maxim static head of 0.88m i.e. When water is. headed to FSL in primary canal and no water in the secondary II canal . The ordinate ii between the HG line and floor level will give the unbalanced head. The maximum up lift pressure in the upstream side will be balanced by the wight of water. Therefore a minimum of 0.3 m of thickness is to be provided to the upstream side. 0 88 Maximum unbalanced head in downstream side =-------- = 0.44m 2 Floor thickness required = 0 44 = 0.352/n Provided 0.40m thickness in the down stream side. _ Q 0.773 Q= — = = 0.67 1.15 1/3 R= 1 35 R= 1.35 R= 1.04m (/ = lassumed) ( f = 1 assumed) 1/3 Depth of scour in the straight reach = 1 25 x R = 1.30m Depth below bed = 1 30 -0.74 D= 0.56m 50 provide 1.1m deep cutoff Protection works Suitable protection shall be provides Blocks length 2D = 2x1.1 = 2.20 say 2.40m 24Provide 4 rows of concrete /masonry blocks of 600m600riix250mm size over 150mm graded basalt. Launching apron Beyond protection work, launching apron shall be provided. The cubic content of launching apron material = 2.25D = 2.25 x 1.1 = 2475 m3/m Keeping apron thickness as 0.6m (600m) Length of apron = 2.475 /0.6 = 4.125 say 4.50m Provide 250mm thick and 0.4m depth stone masonry wall between block protection and launching apron. Upstream protection Block Protection: the upstream protection shall be provided to cater for scour depth D= 1.1m below floor level. Length of block protection = 1.0D = 1.1m say 1.20m Provide two rows of 600x600x250 cement concrete or stone masonry blocks. Launching apron Cubic content of launching apron = 2.25D m3 = 2.25 x 1.1 =2.475 m3/m Provide 600mm thick ness Length of launching apron = 2.475 /0.6 = 4.125m Provide 4.5m length of apron Provide 250mm thick 500mm deep wall between block protection and launching apronI I 1 1 1 1 I I I I V. ESCAPE STRUCTURE Hydraulic Design of escape structure (a) Important Parameters Full supply discharge at escape site = '■ 2.49 m3/sec Bed width of canal Full supply depth Side slopes Location of escape Velocity in canal Slope of canal Silt factor FSL of the primary canal at its head = 2 50m = 1.05m = 1.5:1 = 4.15km chainage of primary canal = 0.58 m/sect = 0.00035 = 1.0 = 1365.0m 26FSL of canal on escape site = 1365 - 0.00035x4150m = 1365 - 1.45m = 1363.55m = 1365.55- 1.05m = 1362.5m Bed level canal = 1363.55 - 1.05m = 1362.5m Taking 60% of discharge of primary canal for escape Discharge of escape channel = 2.49 x 0.60 = 1.494 m3/sec Say 1.50m3/sec (b) Crest Length Crest of escape is kept at the bed level of canal to facilitate the quick depletion of parent channel. Crest of escape will function as broad crested weir Q= c(L-0.1nH) H3/2 Where L = Total clear waterway n= no of end contraction H= Head over the crest C= coefficient of discharge for broad crested weir = 1.70 1.50= 1.705 ( L-0.1 x 2x1.05) 1.05 3/2 1.50 = 1.705 ( L-0.21) 1.076 L= 1.50 1.705x1.076 + 0.21 L= 0.817 + 0.21 L= 0.917m Provide crest length of 0,92m Provide vertical left gate having 1120mm wide and 1150mm high gate with side rollers. , Provide hoisting arrangement at the operating platform 27< The elevation of operating platform is kept at such a level where clearance of the half of height of gate is available. Elevation of lifting platform = 1362.5 +2 xl.15 + = 1365.375 m The crest length is 0.92m, the operating platform is provided 200mm support on both sides. The total width of operating plat form shall be = 0.920+ 2x 0.2 = 1.320m The size of operating platform may be kept as 2.5m x 1 5m and thickness as 150mm The canal section at the escape starching will be rectangular, suitable transition shall be provided on upstream and downstream to change the canal section from normal trapezoidal section to rectangular section; Area of trapezoidal canal section = 2.50 x 1.05 + 1.05 xl.575 = 2.625 + 1.653 = 4.278 2.49 Velocity =-------- = 0.5 8m/sec 4.278 Velocity head = — = [ °'58) = 0.0171m 7 2g 1^2x9.81) Level of total energy line in upstream side = 1362.5+ 1.05 + 0.0171 = 1363.567 m Area of rectangular section = 2.50 x 1.05 = 2.625 m2 2 49 Velocity = —— = 09485m/ sec 2.625 28Area pf rectangular section = 2.50 x 1.05 = 2.625m2 Velocity = — — = 0.9485m/sec 2 49 : 2.625 Loss of head in contraction = 0.2 >/-K2 2> _ Q 2 TO,899-0.336^ V 2x9 81 J = 0.0057 Level of total energy line at the end of contraction = 1363.567-0.0057 = 1363.56 Since the length of canal from end of contraction to start of expansion is kept only 25.30m. Hence three will be negligible loss is rectangular portion of canal Therefore level of total energy line at the beginning will be 1363.56m Loss head in expansion = 0.3 I J = 0.3 0.94852 -0.582' 2<7 = 0.0085 The level of total energy line at the downstream end of expansion will be = 1363.56 - 0.0085 = 1363.555 FSL = 1363.555 - Velocity headI I I I = 1363.536m Bed level = 1363.536- 1.05 = 1362.486 I I I Clear opening for gate = 2.5m Gate of size 2.7m width and 1.15m height may be provided. Provide 200mm support to the slab of gate operating platform the total width of scale = 2x0.2+2.50 = 2.90m I Provide gate operating platform of 2.9m x 2.5m I I I I I I I I I I I I I Level of operating plate form = 1362.5 + 2x 1.15 +^-^= 1365.375 2 Case I: Primary Canal is Closed Floor length Water level in primary canal = 1363.55 Bed level of canal in downstream side = 1362.486 Head = 1363.55-1363.486 = 1.065m Taking Blight’s coefficient = 7 Total floor length = 7x1.065 = 7.455m Provide 10.0m long floor, 5.0m upstream of gate and 5.0m downstream of gate Vertical cut off The minimum depth of upstream and downstream cutoff for this range of discharge = 10m, hence provide 1.1m deep vertical cutoff on upstream i.e. upto R.L 1362.50 -1 1 = 1361.4m 30Provide 1.1 m deep vertical cutoff an downstream side, The level of cutoff 1362.486 1.1 = 1361.386m Floor Thickness Draw hydraulic gradient line at 1:7 for the maximum static head (1363.55 — 1362.486) 1.064m i.e. when the water is headed up to FSL on up stream side and these is no water on the downstream side. The (ordinate between H.G line and floor level would give the unbalanced head. The upstream hydrostatic pressure will be balanced by the weight of water. Provide minimum thickness of 0.3m on up stream side of the gate Maximum unbalanced head = 1363.55-1362.486 2 1.064 = 0.532m 2 Floor thickness required = os321.25 1.25 Provide 0.5m thick floor upto 2.5m length and 0.3m in remaining 2.5m upto the downstream end. Downstream Protection Q= discharge per unit width 2 49 3 Q= —— = 1 0m3/sec 1.0 m /sec 2.5 31I I I I I I I I I I I I I I I I = 1.34 (f= 1.0 assumed) Depth of scour for straight reach - 1.25R = 1.25 x 1.34 = 1.675 m Depth below bed = 1.675 - 1.05 = 0.625m Provide 1.1m deep cutoff Downstream of the impervious floor, suitable protection is to be provided in a length 2xD = 2x 1.1 =2.2m Provide four rows of cement concrete blocks of 600x 600x250 mm size over 250mm thick well graded blanket. Beyond protection work launching apron shall be provided. The cubical content of launching apron will be 2.25 x D m3/per meter length. Cubical content = 2.25 xl.l = 2.475 m3/m Keeping 0.6m as thickness of launching apron, the length will work out to 2 475/0.5= 4.95m Provide 5.00m length of apron Provide 250mm thick and 600mm deep sline masonry wall between block protection and launching apron. Upstream Protection I The upstream protection work shall be provided to cater for the scour depth of D= 1.1m I below the floor. Depth of block protection on upstream side= 1.0 x D i.e 1.1m so provide 2 raws of 600*600x250 stone masonry blocks over 250mm well graded ballest. I I I 32Launching apron Cuibic content of launching apron = 2.25D Volume /m = 2.25 xl. 1 = 2.475 m3/m If the thickness is 600m T , 2.475 „ Length = -------- = 4 95m 0.5 Provide 5.0m length of 600mm thick launching apron provide 250mm thick 600mm deep wall between launching apron and block protection, Case II - When Escape is closed FSL of Primary Canal = 1363.55m Bed Level of Escape Channel = 1362.50 Water Head = 1363 - 1362.50 = 1.05m Taking Blights’ coefficient Total length of floor = 7.0 7 x 1.05 = 7 35m Provide 5.0 m floor upstream side of gate and 5.0m on downstream side Vertical cut off The minimum depth of up stream and downstream cut off for this range of discharge = 1.0m Provide 1.1m deep vertical cut off on the upstream side and 1.1m deep vertical cutoff on the downstream end of cutoff. R.L of upstream cut off = 1362.50- 1.1 = 1361.40m R.L of down stream cut off = 1362.5 - 1.1Floor Thickness Provide 0.3m floor thickness on the upstream side of gate Maximum unbalance head in the just downstream point of gate = = 1.05/2 = 0.525 Floor thickness required = 0.525 = 0.42m 1.25 Provide 0.45m thickness up to 2.5m downstream of the gate and 0.30m thickness up to the end of the floor Downstream Protection q = Q/6= 1.50/0.92 = 1.63 R = 1.34 ( q2 ) 1/3 assume f = 1.0 f R = 1.34 (1.38) R=1 855 For straight reach depth of scour = 1.25 x R = 1.25 x 1.855 = 2.32m Depth below bed =2.32-1.05 D = 1.27m Provide 1.30m deep cut off.Protection is to the provided in 2 2 D length ( i.e 2 x 1.30 = 2.60 say 3.00) by cement concert blocks in five rows of 600 x 600 x 250 mm size laid over 250mm graded ballast. Beyond protection work launching apron shall be provided The cubic content of materia s launching apron will be 2.25D cubice meter / meter length Cubic Content = 2.25D = 2.25 x 1.30 = 2.925m3 / m Keeping the thickness of launching apron as 0.5m Length of apron = 2.925 = 5.85 say 6.0m 0.5 Provide 250mm 600mm deep stone masonry wall between block protection and launching apron. Upstream Protection: upstream protection is required as Cement concert flour of primary canal exists in the upstream said No damage is expected in the upstream side. Fig 8. Escape structureLOOTUONAL SECTION B-B I I 36 C roadway3 VI. BRIDGE Hydro lice Design of Harer / Babile Road Bridge Over Primary Canal (a) Canal parameters Location = change 5 + 900 primary canal Discharge = 2.49m /m Bed width = 2.40m Depth = 1.04m Side slope = 1.5: 1 Longitudinal slops = 0.0035F FSL at off take point = 1365.0 FSL at Read crossing = 1365.0 - 5.9 x 0.00035 = 1362.935m Bed level of canal = 1361.89.5m The canal section is given transition from trapezoidal and rectangle on up stream side of bridge and from rectangle to trapezoidal in the downstream side Clear span of bridge = 1.04m Provide overall depth of SLas = 300m Free board provide in canal = 400mm Provided extra free board of 400mm } Total Free board = 800mmLevel ofbottom slab = 1362.935 + 0.80 = 1363.735 Level of the top of bridge = 1363.735 + 0.30 = 1364.035m (b) Design of Abutment Scour depth below cannel bed = Depth / 3 = 1.04/3 = 0.35m say 0.4 m Level of scoured bed = 1361 89 - 0.4 = 1361.49 Depth of scoured bed below Road Level = 1364.35- 1361.49 = 2.545 - say 3.0m Width of abutment at scour level = 0.7 depth of scour bed level or road level = 07x3.0 = 2 10m (c)Upstream Protection Upstream cut off Minimum depth of cut off below upstream bed level of canal for 2.45m3 /sec discharge =1.0 Provide 1.1m deep cut off Level ofbottom of cutoff = 1361.895 - 1.1 = 1360.795 Upstream Block Protection Two rows of 600 x 600 x 250mm C.C blocks over 250mm graded ballast may be provided. 383 Upstream Launching Apron Quantity of apron / m = 2.25Dm / m = 2 25 x 1 1 = 2.475m3 / m Provided 600mm thick apron Length of apron = 2.47510.6 = 4.125m say 4.50m Provide 600mm thick apron for 4.50m length Provide 300mm thick and 0.5m deep wall in between block protection and launching apron. (d) Downstream Protection Cutoff Minimum depth of cut off below d/s canal bed for 2.49m3 I sec Discharge = 1 0m Provide 1.1m deep cut off. Level of batton cut off = 1361.895 -1.1 = 1360.795 Block Protection Provide 4 rows of 600 x 600 x250 cc blocks laid over 250 thick graded blankets. Lunching Apron Quantity of apron per meter = 2.25D m3 = 2.25 x 1.1 m3 = 2.475 m 3 Provide 600mm thick apron Apron length = 2.475 I 0.6 = 4.125m say 4.5m 39 1Provide 600 mm thick launching Apron of 4.5m length Provide 300mm thick and 0z5m ■' deep wall between block Protection and launching apron. This bridge is structurally design for heaviest type of loading as it is main road. It is to be designed with RCC decking and masonry substructure. As per span consideration it is very small bridge therefore the foundation shall consist of cement concrete floor with curtain walls 1 errtoarfcrrert 5 made of unoompacted random (iU 2 Earth of ocrwbxcton be lemared from r*w sale 3 The dstance of borrow area shaft not be less than 25.0m from heei/toe cf embawteri Fig 9 Flood Protection Embankment 40I I I I I I I I I I I I I I I Fig 10 RCC Pipe Culvert PLAN I Section A-A I I Fig 11. Slab Culvert I 41 Section B-BI I I I I ! I S4C»>n A-A I Fig 12. Slab Culvert Across Primary canal I I I I I I I I I I I w I Fig 13. Pipe turn out 42 .>Details of Tertiary canal Head Regulators Name of Tertiary canal Off taking Point Name of parent channel Hydro lice Parameters at off taking points Q m /s 3 b(m) d(m) bl (m) dl (m) P (cm) T,P 13.300km of primary c. Primary C 2.0 2.13 1.0 0.154 ___ 0.53 0.4] 30 T, S2 3.500km of S-ff Secondary C -II 0.705 1.08 0.72 0.069 0.45 0.29 20 Ti S| 1.500km ofS-I Secondary C-I 0.968 1.20 0.82 0.126 0.48 0.39 25 T 2 S| 5.500km ofS-I Secondary C-I 0.552 1.10 0.64 0.072 0.46 0.30 120“ T,„ 7.550km ofS-I Secondary C-I 0.189 0.80 0.41 0.072 0.46 0.30 25 B- -.. * ♦■ —L Section A-A Fig 14. Distribution box in quaternary canal 43vn. DROP STRUCTURES To Erer project vertical drop/ falls which have no glacis or sloping floor downstream of the crest are recommended. The dissipation of energy is achieved by impact of falling water on the cushion of water specially created for the purpose. The energy is dissipated by means of impact and deflection of velocity , suddenly from horizontal to vertical direction. The cushion is formed by depressing the floor below the downstream head of channel. The following dimensions are formed suitable and therefore recommended in computation of drop strictures. Cistem Length (L) = 5 (Hl xD) 0 5 Cistern depth (x) = 1_ (Hl xD) 2/3 4 Where HL = drop in meter D = depth of west below upstream T.E.L. in m L = the length of cistern in m x = is the depression below down stream bed of channel. On the basis of this formula cistern dimension i.e. length and depression depth are worked out for drop depth of 1.0m. These have been worked out for earthen canals having bed slope 0.00045, Manning’s n = 0.025 and side slope 1; 1. The same may be provided at appropriate places in Quaternary canals, drains where ever the discharge matches with the one indicated in the table given on the drawing of drop structure. 44However incase of Secondary canal -I which is required to descend about 48m in about 1.0km length a server of drop structure ( about 32 in no) of 1.5m drop are recommend. The cistern dimensions are calculated below Secondary Canal -I parameters Discharge = 0.968 m3 / sec Velocity = 0.49 m/s Depth of flow = 0.82m Bed width = 1.20m Side slope = 1.5:1 Slope = 0.0004 Manning’s = n = 0.025 Free board = 0.3 m Cistern Length (L) = 5 (H X D ) L 2 05 D = depth + Velocity head (V )/2g ’ ’ 2 = 0 82+ (0.49) / (2x9.81) = 0.82+01 = 0 83m HL= 1.5m L = 5 (0.83 X 1.5)O3 L = 5.58 m provide L = 5.60” Depression depth below downstream, bed level of canal X = !4 (HlXD)^ X= % ( 1.5X0.83) 2/3 X = !4 (1.158) X = 0.289m Provide 0.30m deep cistem. Provide 2.5m length of pitching on the bed and side of canal in the upstream side of drop stricture and 2.0m in the down stream side. 45 iI OQL Oil FIL Of CBL *00. S e ctio n A -A TIL ••L Section B-B Fig 15 Typical Drop Structure 46No 3 Q m /se Bed with (m) Depth (m) • Cistern size Length (m) Depth (m) Pitching Length L| Upstream Pitching length d Lj down stream 1 0.03 0.35 0.23 2.39 0.09 2.0 1.5 2 0.05 0.45 0.27 2.59 0.10 2.0 1.5 3 0.075 0.50 0.33 2.87 0.11 2.0 1.5 4 0.10 0.58 0.36 To~ 0.12 2.0 1.5 5 0.25 0.82 0.41 3.1 0.14 2.5 2.0 6 0.50 0.86 0.43 3.28 0.15 2.5 2 0 7 1.0 1.22 0.61 3.63 0.16 2.5 2.0 8 2.0 1.56 0.78 3.90 0.17 3.0 2.5 • bed width and depth of channel are for trapezoidal earthen channel ,side slope 1:1, bed slope 0.0045, manning n=O.O25 VOL AQUEDUCT FOR SECONDARY CANAL - H ON DENCITO RIVER Design data (a) Canal: Trapezoidal earthen canal Discharge = 0.773m /sec Bed with = 1.15m Velocity = 0.46m/sec Side slope = 1.5:1 Slope = 0.0004 Manning’s Coefficient (n) =0 025 Depth = 0.74 (b) River Flood Discharge ( Tr= 100yr) = 267.5m 3/sec 3 High flood level = 1.2M above Bed Level River bed level = 1354.5 (as informed) 47(c) Type of Structure Proposed The earthen banks are discontinued and the cannel is taken in a rectangular trough supported on piers. This is adopted to affect overall economy. (d) Drainage Waterway Lacy’s Regime Perimeter P =4.83 P = 4.83 V267.5 P = 79.0m Let clear span between piers is 6.0m and there are 11 spans and ten piers. Clear water way =11x6 =66m Provide lOpiers of 1.0m with. Total water way between abutments = 66+ 10 x 1.0 =76m (e) Canal Waterway For reason of economy the trapezoidal section of earthen canal is rectangular section The clear width of trough = 1.15m, same as width of canal Flow Area of trapezoidal Section = 1.15 x 0.74 + 1.11 x 0.74 = 0.85 + 0.82 = 1.67m2 Dimensions of rectangular section = 1.15 x 0.74 = 0.8436m2 Provide 1:2 splay in contraction and 1:3 in expansion, because the canal is very small in size. 48Note: All dimensions are in meters (f) Head loss and bed levels at different sections Velocity at section 1-1 = 0.46m/sec Velocity at section 2 - 2 = 0.773 2/0.8436 = 0.91m /sec Head Loss in Contraction = J --------------- 2g z2 (r2 -n ) L = (o.91 -0.42 )r0.2 zz 2x9.81 =0.006m (K3 -r4 ) 22 Head Loss in expansion = 0.3 ' 2g = 0.009m Head Loss in rectangle section: Use managing equation V= l/nRMSw R= A/P = 1,15x07 1.15 + 2x0.74 = 0,85 = 0.32m 2.63 n = for concrete surface = 0.015 490.91 = (0.32)2/351/2 0.015 S =0,91 x 0.015 = 0.029 0.466 S = 0.008 Head loss in strength of Length of 76m = 0.0008 X 76 = 0.06 Secondary Canal crosses river Decho at Chainage 3+000 FSL in Secondary Canal at its head = 1360.16 FSL in Secondary Canal at 3 km d/s = 136016 - 1.12 (Slope = 0.004) =1359.04m 2 Elevation Total Energy line = FSL + Velocity head =1359.04 + (0.46) / (2x9.81) = 1359.04+0.01 = 1359.05m Bed level of canal at 1-1 1358.30 Head loss in contraction between 1-1 and 2-2 = .006 Head Loss in trough = 0.06 Head Loss in Expansion = 0.009 Elevation on of total energy line at section 4-4 = 1359.05 - (.006 + 06+.009) = 1359.05 -0.075 =1358.975 Bed Level at section 4-4 = 1358.975—depth of flow = 1356.975 - 0.7= 1358.235 50The loss of head in expansion, contraction and trough is negligible. Therefore the bed level of channel before and after trough remains partially same. Through: The size of trough will be 1.15 x 1.05m assuming 30cm free board The walls of trough are propose as 0.30m thick to be constructed in Reinforced comment concrete (RCC), For small Channels of this size 0.30m free board is quite sufficient. - H------------- Joints should he provide across and along the trough length. The maximum spacing of joints in this direction should be limited to 20m. A gap of 15mm with water stops at all the joints across and along the length should be to accommodate movements. PIERS and ABUTMENTS Piers and abutments are proposed of stone masonry using 1:4 cement mortar. The recommended thickness of piers for span 5 to 6m is 0.85m Hence 1.0 thickness is recommended. Provide 1,0m thick pier from top to 1.0m below river bed level. The pier width shall be increased to 1.6m in two steps. Foundation concert of 1.0m is provided below the piers. A concrete base of 2.2m wide and 1 0m thick shall be provided at the foundation level. On the top, a cement concrete bed block of 0.2m thickness shall be provided, which will be projecting to 0.15m outside on all directions. The piers shall have semi circular nose and cut water radius of 0.5m I I I I 51R=0.5 <--------------------------------- ► 2.0 Note: All dimensions are In meter The width of abutment at scour level should be approximately 0.6 times the scour depth below FSL. The abutment shall stand the earth pressure of dry soil above the pressure gradient line and submerged soil below the line The width of abutment shall increase in step starting from 570 mm from the top and increasing to 1100mm at the top level of foundation concert of 600mm thickness Foundation concrete of 1800m wide and 600m deep shall be provided below abutment level. Depth of Foundation Norma depth of scour according to Lacy’s equation is R = 0.47 er ( f- 15 for river bed material) R= 0.47 (267.3') M'3 R = 2.59 Anticipated depth of soccer around pier = 2R = 2X2.59 = 5.18m The minimum depth of foundation below anticipated scour level should not be less than 1.0m or 1/3 of scour depth, which ever maximum 52Hence Depth of foundation below HFL -5.18 + 1.0 = 6.18m Level of foundation concrete will be HFL River -6.18m HFL of river is 1.2m above the bed level as observed at the site. Depth of foundation = 6.18—1.2— 4.98 Say 5.0m below bed level Wing wall The width of wing wall at scour level is taken as 0.4 times the scour depth below HFL. The top shall be provided with 0.20m thick coping width c.c (1:2:4) Provide 50mm diameter holes at of interval of 3.0m approximately. 53JI Fig 16. Aqueducts on Secondary canal 1 I I I I 54IX Inverted Siphon Out of the total cross drainage works, when the high flood level of the natural darin is higher than the bed level of the crossing channel 14 siphons are proposed. The structures mainly consist of inlet transition, circular barrel and outlet transition. a. Design Consideration i. The velocity of water in the siphon is kept greater than 1 m/s to prevent silting in the barrel. ii. Water surface at the enterance is kept about - (where V2 is the velocity in the barrel) or a minimum of 0.30m about the top of siphon barrel to prevent air entering in to the barrel. iii A minimum earth cover of 0.60m below drain bed level is provided iv. A trash screen is proposed to be instoled at the inlet to prevent the barrel from clogging b. Hydraulic Design 1. Cross Sectional area sizing The discharge formula controlled by orifice inlet is given by:- Q=cA7eiA Where Q= Discharge (m3/S) A= Sectional area of the pipe (m2) h= Driving head (m) C= Coefficient = 0.81 2. Head Loss i. Friction loss Friction loss in the inlet transition, barril and outlet transition can be determined by the average friction slope, using Manning’s equation and the total loss may be attained by multiplying the respective horizontal length.Where: - n - manning’s roughness coefficient V= Flow velocity (m/s) R= Hydraulic radius (m2/m) L= Horizontal length (m) Sf= Friction slope (m/m) Hf= Friction loss (m) ii) Minor loss • Convergence at inlet transition -m • Divergence at outlet transition • Barrel bend loss 2g Where : VI = Velocity at inlet V2 = Velocity at barrel V3 = Velocity at outlet g= acceleration due to gravity The Hydraulic parameter of all Siphons is calculated and the result is summarized as shown in the table below.Table IX-1 Hydraulic Parameter No Name of Siphon Discharge (m3/S) Pipe Diameter (m) Flow velocity in the pipe (m/S) Head loss (m) Number of pipe 1. CD5-P 2.49 1.05 1.4 0.25 Double 2. CD6-P 2.49 1.05 1.44 0.24 Double 3. CD7-P 2.38 1.05 1.30 0.22 Double 4. CD11-P 2.21 1.05 1.29 0.18 Double 5. CD16-P 2.00 1.05 1.15 0.15 Double 6. CD2-S1 0.765 0.90 1.21 0.18 Single 7. CD3-S1 0.65 0.90 1.10 0.12 Single 8. CD4-S1 0.65 0.75 1.47 0.29 Single 9. CD1-S2 0.773 0.90 1.22 0.18 Single 10. CD4-S2 0.555 0.75 1.26 0.22 Single 11. CD6-S2 0.418 0.60 1.48 0.33 Single 12. CD7-S2 0.30 0.60 1.10 0.17 Single 13. CD8-S2 0.221 0.45 1.40 - 0.36 Single 14. CD9-S2 0.221 0.45 1.40 0.36 Single> -Qoo< ^40 ) bj4o it i 81 1 i * - vtMtNILU___________ STONE PITCHING PRY STQME PITCHING C-20 CONCRETE NOTES: Section 1. ALL DIMENSIONS ARE IN MM . LEVELS ARE IN METER UNLESS OTHERWISE SPECIFIED 2. FOR PIPE DETAIL SEE -DWG No009 FEDERAL DEMOCRATIC REPUBLIC OF ETHIOPIA MINISTRY OF WATER RESOURCES COMrrftT ENGINEERING and consulting enterprise !$>, IN ASSOCIATION WITH CONSULTING ENGINEERING SERVICE ( INDIA ) PVT. LTD L— PROJECT- ERER IRRIGATION PROJECT DETAIL DESIGN TITLE: - INVERTED SIPHON STRUCTURE (TYPE 2) SURVEYED ] BY. DATE May 2009 DRAWN BY TOMASG SCALE DESIGN BY: S YADA.WN6H LEVEL DETAIL APPROVED BY; A.MEU0«STE DRAWING ERARR/CST-10Table: Original ground level 300.63 300.23 299.57 298.86 298.16 297.5 296.83 300.45 299,64 299.16 301.1 300.48 299.69 298.9 298.24 297.43 297 296.52 295.68 295.31 294.68 294,2 293.63 300.12 299 298.33 297.75 297.22 296.68 296.14 297.9 297.35 299,85 299.22 298.64 298 297.36 296.71 296.16 295.6 299.44 298.82 298.21 297.64 297.01 296.5 295.93 295.38 298.49 297.8 297.29 296.74 297.3 296.73 296.32 295.79 295.17 294.58 293.95 293.39 295.01 294.5 293.88 293 21 294,62 295.63 295.06 294.63 296.24 295.75 295.28 294.75 296.17 295.62 295.1 294.65 294.21 293.8 293 292 58 292.23 292.58 291.97 294.35 293.81 293.29 292.62 291.86 291.9 1 5032.77 25 125819 25 291.34 291.02 2 5028.09 75 377106.75 292 59 291.8 290.96 290.4 "3 5024.34 125 628042 5 291.1 290.29 4 5021.19 175 878708,3 294,17 293.73 293.26 292.71 292 291.19 290.4 5 5017.56 225 292.68 292.05 291.27 290.5 6____ 5012.94 275 298.54 297.95 297.38 296.8 296.23 295.73 295.29 294.87 294.4 293.94 293.64 293.39 293 292.38 291.74 291.1 290.46 7 296.81 296.22 295.69 295.21 294.76 294.36 294.3 293.93 293.6 293.11 293.98 293.59 293.3 293.05 292.57 292 291.34 290.76 290.12 8 1128951 1378558.5 5006.84 4999.01 325 375 1627223 1874628.8 293.41 293.08 292.82 292.53 292.13 291.55 290.94 290.33 289.73 9 4990.1 425 2120793Determination of the plane of the best fit Where, O=distance from reference line H=grid level n=total number of grids 48353914 £(W 64451916 (£d,)(2»= 48145360 94084375 70624375 (Eo.xxhJ /„ = 65137840 I c>: t MW'" I I IDetrmlnation of cut & fill Detrmlnation of cut & fill Q 0.911 0.781 P 0.511 0.301 0 0.081 -0.119 N -0.299 -0.529 M -0.739 -0.899 3 4 6th unit 8th unit M 298 297.64 M 297.64 297.22 L 297.36 297.01 L 297.01 296.68 K 296.71 296.5 K 296.5 296 14 J 296.14 295.91 J 295.91 295.48 3 4 4 5 Determina Determinati Centroid level= Centroid point is K&L. 3&4 595.64 594.37 593.21 59205 2375.27 296 90875 Centroid level= Centroid point is K&L. 4&5 594 86 593.69 59264 591.39 2372.58 296.5725 M 297.30875 297 10875 M 296 9725 296.7725 L 297.10875 296.90875 L 296.7725 296.5725 K 296.90875 296.70875 K 296.5725 296.3725 J 296.70875 296.50875 J 296.3725 296.1725 3 4 4 5 Detrmination of cut & fill Detrmination of cut & till M 0.69125 0.53125 M 0.6675 0.4475 L 0.25125 0.10125 L 0.2375 0.1075 K -0.19875 -0.20875 K -0.0725 -0.2325 J -0.56875 -0.59875 J -0.4625 -0.6925 3 4 4 5 9th unit 11lh unit Q 299.64 299.16 O 299.16 298.49 298.54 P 299 P 298.49 O 298.33 297.8 297.95 O 297.8 N 297.75 297.29 297.38 N M 297 22 296.74 297.29 296 8 M 296.74 5 6 598 8 597 49 596 13 595 04 593 96 2981 42 296.23 6 7 597 7 596 44 595 18 594 09 592 97 2976 38I I I I Determination of Formation level Centroid level= Centroid point is O, 5&6 298.142 Determination of Formation level Centroid level= Centroid point is O, 6&7 297.638 Q 298.642 298.442 Q 298.138 297.938 P 298.442 298.242 P 297.938 297.738 O 298.242 298.042 O 297.738 297.538 N 298.042 297.842 N 297.538 297.338 M 297.842 297.642 M 297.338 297.138 5 6 6 7 Detrminat Dctrmlnati Q 1.022 0.602 P 0.552 0.212 O 0.062 -0.158 N -0.248 -0.538 M -0.598 -0.908 6 7 12th unit M I I I I I I I I I I I I 593.96 592.92 591.89 590 74 2369 51 296 18875 296.74 296.23 L 296.24 295.73 K 295.75 295.29 J 295.26 294.86 6 7 Determination of Formation level Centroid lcvel= Centroid point is K&L. 5&6 Determination of Formation level Centroid level= Centroid point is K&L. 6&Z 592.97 591.97 591.04 590 12 2366 1 295.7625 M 296.58875 296.38875 M 296.1625 295.9625 L 296.38875 296.18875 L 295.9625 295 7625 K 296.18875 295.98875 K 295.7625 J 295.98875 295.78875 295.5625 J 295.5625 295.3625 5 6 6 7 Dctrmination of cut & fill Dctrmination of cut & fill M 0.63125 0.35125 L 0.29125 0.05125 K -0.04875 -0.23875 J -0.50875 -0.52875 5 6For the first two blocks 1st unit Table: Original ground level 3rd unit Q 301.1 300.83 P 30048 300.23 O 299.69 299.57 N 298.9 298.86 M 296.24 298.16 1 Determination of Formation level Centroid level= Centroid point is O, 1&2 J 601.93 600.71 599.26 597.76 596.4 2996.06 299.606 Determination of.Formation level Centroid level= Centroid point is O, 2&3 601.28 600.08 598.79 597.5 596 16 2993.81 299.381 Q 300.106 299.906 P 299.906 299.706 O 299.706 299.506 N 299.506 299.306 M 299.306 299.106 1 2 Detrmination of cut & fill Detrminati Q 0.994 0.924 P 0.574 0.524 O -0.016 0.064 N -0.606 -0.446 M -1.066 -0.946 1 2 2nd unit 4th unit M 298.24 298.16 L 297.43 297.5 K 297 296.83 J 296.53 296.32 1 2 596.4 594.93 593.83 592.85 2378.01 M 298.16 298 L 297.5 297.36 K 296.83 296.71 J 296.32 296.14 2 3 596.16 594.86 593.54 592 46 2377.02Determination of Formation level Centroid level= 297.25125 Centroid point is between K&L, 1 &2 Determination of Formation level Centroid level = Centroid point is K&L, 2&3 297.1275 M 297.5275 297.3275 L 297.3275 297.1275 K 297.1275 296.9275 J 296.9275 296.7275 2 3 Detrminatlon of cut & fill Dctrmination of cut & fill M 0.6325 0.6725 L 0.1725 0 2325 K -0 2975 -0.2175 J -0.6075 -0.5875 2 3 Sth unit 7th unit Q 300.45 300.12 Q 300.12 299.64 P 299.85 299.44 P 299.44 299 O 299.22 298.82 O 298.82 298.33 N 298.64 298.21 M 298 297.64 3 4 600.57 599.29 598.04 596.85 595.64 2990.39 N 298.21 297.75 M 297.64 297.22 4 5 599.76 598.44 597.15 595.96 594 86 2986.17 Determination of Formation level Determination of Formation level Centroid level= 299.039 Centroid point is O. 3&4 Centroid level= 298.617 Centroid point is F2, 4&5 Q 299.539 299.339 Q 299.339 299.139 299.117 P 298.917 P 0 299.139 298.939 298.917 298.717 O N 298.939 298.739 298.717 298.517 N M 298.739 298.539 298.517 298.317 3 4 M 298.317 298.117 4 5 »J 3th 15th unit Q 297.9 297.3 Q 298.54 297.9 P 297.95 297.35 O 297.38 296.81 N 298.8 296.22 M 296.23 295.69 7 8 Determination of Formation level Centroid level= Centroid point is O, 7&8 596 44 595.3 594.19 595.02 591.92 2972 87 297.287 P 297.35 296.73 O 296.81 296.17 N 296.22 295.62 M 295.69 295.1 89 Determination of Formation level Centroid level= Centroid point is O, 8&9 595.2 594.08 592.98 591.84 590.79 2964 89 296.489 Q 296.989 296.789 Q 297.787 297.587 P 296.789 296.589 P 297.587 297.387 O 296.589 296.389 O 297.387 297.187 N 296.389 296.189 N 297.187 296.987 M 296.189 295.989 M 296.987 296.787 8 9 7 8 Detrmination of cut & fill Dctrmlnation of cut & fill Q 0.911 0.511 Q 0.753 0.313 P 0.561 0.141 P 0.363 -0.037 O 0.221 -0.219 O -0.007 -0.377 N -0.169 -0.569 N 1.613 -0.767 M -0.499 -0.889 M -0.757 -1.097 8 9 7 8 16th unit 14th unit M 296.23 295.69 L 295.73 295.21 K 295.29 294.76 J 294.86 294.35 7 8 Determina Centroid level= Centroid point is K&L, 788 591.92 590.94 590 05 589 21 2362.12 295 265 M 295.69 295.1 L 295.21 294.65 K 294.76 294.21 J 294.35 293 75 8 9 Determinati Centroid level= Centroid point is K&L, 8&9 590 79 589.86 588.97 588 1 2357.72 294.715 M 295.665 295.465 M 295.115 L 295.465 295.265 294.915 L 294.915 K 295.265 295.065 294.715 K J 295.065 294 865 294 715 294.515 J 294.515 7 8 294.315 8 9Dctrmination of cut & fill Dctrmination of cut & fill M 0.565 0.225 M 0.575 0.185 L 0.265 -0.055 L 0.295 -0.065 K 0.025 -0.305 K 0.045 -0.305 J -0.205 -0.515 J -0.165 -0.565 6 7 8 9 17th unit 19th unit Q 296.72 296 Q 297.3 296.72 P 296.12 295.4 P 296.73 296.12 O 295.56 294.84 O 296.17 295.56 N 295 294.25 N 295.62 295 M 294.53 293.78 M 295.1 294.53 10 11 9 10 Determination of Formation level Centroid level= Centroid point is O, 9&10 594.02 592.85 591.73 590.62 589.63 2958.85 295.885 Determination of Formation level Centroid level= Centroid point is O, 10&11 592.72 591.52 590.4 589.25 588.31 2952.2 295.22 Dctrmination of cut & fill Dctrmination of cut & fill Q 1 0.48 Q 0.915 0.535 P 0.6 0.08 P 0 545 0.135 O 0.24 -0.28 0 0.185 -0.225 N -0.12 -0.165 -0.585 -0.67 N M -0.39 M -0.485 -0.855 -0.94 9 10 9 10 • i.-i J ’ ■ '27th unit 25th unit Q 293 292 Q 294.02 293 P P 293.43 292.42 0 292.84 291.84 N 292.32 291.33 M 291.82 290.82 587.02 585.85 584.68 58365 582 64 2923.84 292.384 292.42 291.43 O 291.84 290.87 N 291.33 290.38 M 290.82 289.87 14 15 I I I I I I 1 I I I I I I I I I 13 14 Determination of Formation level Centroid level= Centroid point is O, 13&14 Determination of Formation level Centroid level= Centroid point is O. 14&15 585 583.85 582.71 581.71 580 69 2913 96 291 396 Q 292.884 290.884 P 292.684 290.684 O 292.484 290.484 N 292.284 290 284 M 292 084 290.084 13 14 Dctrmination of cut & Fill Dctrmination of cut & fill Q 1.136 2.116 P 0.746 1.735 O 0.356 1.356 N 0.036 1.046 M -0.264 0 736 13 14 28th unit M ,290.82 289.87 L 290.36 289.33 K M 291.82 290.82 289.5 288.82 J 289.39 288 36 L 291.3 290.36 K 290.84 289.5 14 15 J 290.5 289 39 13 14 582 64 581.66 580.34 579 89 2324 53 Determination of Formation level Centroid level= 580.69 579.69 578 32 577.75 2316 45 289 55625 Centroid point is K&L. 14& 15Determination of Formation level Centroid level= Centroid point is K&L, 13&14 290.56625 Detrmlnation of cut & fill Detrmlnation of cut & fill 31 st unit 27th unit Q 291 290 P 290.45 289.4 Q 292 291 583 561.88 580 76 579 77 578 74 2904 15 290.415 O 289.89 288.9 P 291.43 290.45 N 289.39 288.37 O 290.87 289.89 M 288.87 287.86 N 290.38 289.39 16 17 M 28987 288.87 15 16 Determination of Formation level Centroid level= Centroid point is O, 15&16 Determination of Formation level Centroid level= Centroid point is O. 16&17 581 579.85 578.79 577.76 576.73 2894.13 289 413 Q 290915 290.715 P 290.715 290.515 O 290.515 290.315 N 290.315 290.115 M 290 115 289.915 15 16 Dctrmination of cut & fillDctrmination of cut & fill Q 1.087 0.287 P 0.737 -0.113 Q 1.085 0.285 O 0.377 -0.413 P 0.715 -0.065 N 0.077 -0.743 0 0.355 -0.425 M -0.243 -1.053 N 0.065 -0.725 16 17 M -0.245 -1.045 15 16 32nd unit 30th unit M 288.87 287 86 M 289.87 288.87 L 288.33 287.33 L 289.33 288.33 K 287.82 286.82 K 288 82 287.82 J 287.32 286.29 J 288.36 287.32 578.74 577.66 576.64 575.68 2308.72 288 59 16 17 15 16 Determination of Formation level Centroid level= Centroid point is K&L, 15&16 Determination of Formation level Centroid level= Centroid point is K&L, 16&17 576 73 575.66 574 64 573.61 2300.64 287.58 Dctrmination of cut & fill M 0.88 0.08 L 0.54 -0.26 K 0.23 -0.57 J -0.03 -0.87 15 1633rd unit 35th unit Q 290 288.73 Q 288.73 286.73 P 289.4 288.21 578.73 577 61 576.59 575.54 574 58 2883.05 288.305 P 288.21 286.3 0 288 9 287.69 O 287.69 286 N 288.37 287.17 N 287.17 285.58 M 287.86 286.72 M 286.72 285.23 17 18 18 19 Determination of Formation level Centroid levcl= Centroid point is O, 17&18 Determination of Formation level Centroid level= Centroid point is O, 18&19 575.46 574 51 573.69 572.75 571.95 2868 36 286 836 Q 288.805 288.605 P 288.605 288.405 O 288.405 288.205 N 288.205 288.005 M 288.005 287.805 17 18 Detrmination of cut & fill Detrmination of cut & fill Q 1.394 -0.406 P 1.074 -0.636 O 0.754 -0.736 N 0.434 -0.956 M 0.184 -1.106 18 19 34th unit 36th unit M 287 86 286.72 M L 287.33 286.25 286.72 285.23 K 286.82 285.8 286.29 285.32 17 18 574.58 573.58 572.62 571.61 2292 39 L 286.25 284.83 J K 285.8 284.45 J 285.32 284.04 18 19 571.95 571.08 570 25 569.36 2282.64Determination of Formation level Centroid level= Centroid point is K&L, 17&18 286.54875 Determination of Formation level Centroid level= Centroid point is K&L, 18819 285.33 M 286.94875 286.74875 L 286.74875 286.54875 K 286.54875 286.34875 J 286.34875 286.14875 17 18 Detrmination of cut & fill Detrmination of cut & fill M 0.91125 -0.02875 M 0.99 -0.3 L 0.58125 -0.29875 L 0.72 -0.5 K 0.27125 -0.54875 K 0.47 -0.68 J -0.05875 -0.82875 J 0.19 -0.89 16 17 18 19 37th unit 39th unit Q 284.5 283.02 Q 286.73 284.5 P 284.03 282.79 P 286.3 284.03 O 283.82 282.6 O 286 283 82 571.23 570.33 569.82 569.18 568.58 2849.14 284.914 N 283.6 282.41 N 285.58 283.6 M 283.35 282.29 M 285.23 283.35 20 21 19 20 Determination of Formation level Centroid level= Centroid point is O, 19820 Determination of Formation level Centroid level= Centroid point is O. 20821 567.52 566.82 566.42 566.01 565.64 2832.41 283 241 Q 285.414 285 214 P 285 214 285 014 O 285.014 284.814 N 284.814 284.614 M 284.614 284.414 19 20 IDetrmlnation of cut & fill Dctrmination of cut & mi Q 0.759 -0.521 Q 1.316 -0.714 P 0.489 -0.551 P 1.086 -0.984 O 0.479 -0.541 O 0.986 -0.994 N 0.459 -0.531 N 0.766 -1.014 M 0.409 -0.451 M 0.616 -1.064 20 21 19 20 40th unit 38th unit M 283.35 282.29 M 285.23 283.35 L 284.83 283.17 K 284.45 283 J 284.04 282.88 19 20 Determination of Formation level Centroid leve!= Centroid point is K&L, 19820 568.58 568 567.45 566.92 2270.95 283.86875 L 283.17 282.13 K 283 282 J 282.88 281.87 20 21 Determination of Formation level Centroid level= Centroid point is K&L. 20&21 565.64 565.3 565 564.75 226069 282.58625 M 284.26875 284 06875 L 284.06875 283 86875 K 283.86875 283.66875 J 283.66875 283.46875 19 20 Dctrmination of cut & fill M 0.96125 -0.71875 L 0.76125 -0 69875 K 0.58125 -0.66875 J 0.37125 -0.58875 19 2041st unit 4 3rd unit Q 283.02 282.29 P 282.79 281.9 0 282.6 281.57 N 282.41 281.39 M 282.29 281.25 21 22 Determina Centroid level= Centroid point is O, 21&22 565.31 564.69 564.17 563.8 563.54 2821.51 282.151 Q 282.29 281.63 P 281.9 280.9 O 281.57 280.56 N 281.39 280.35 M 281.25 280.21 22 23 Dcterminati Centroid level= Centroid point is O, 22A23 563 92 562.8 562.13 561.74 561.46 2812.05 281 205 Q 282.651 282.451 Q 281.705 281.505 P 282.451 282.251 P 281.505 281.305 O 282.251 282.051 O 281.305 281.105 N 282.051 281.851 N 281.105 280.905 M 281.851 281.651 M 280.905 280.705 21 22 22 23 Dctrmination of cut & fill Detrmination of cut & fill Q 0.369 -0.161 P 0.339 -0.351 O 0.349 -0.481 N 0.359 -0.461 M 0 439 -0.401 21 22 42nd unit 44th unit M 282.29 281 25 M L 282 13 281.1 281.25 280.21 L 281.1 K 282 281 J 281.87 280.78 21 22 563.54 563.23 563 562.65 2252.42 280 1 K 281 279.96 J 280.78 279.74 22 23 561.46 561.2 560.96 560.52 2244.14Determination of Formation level Centroid level= Centroid point is K&L, 21&22 281.5525 Determination of Formation level Centroid level= Centroid point is K&L, 22823 280.5175 Detrmination of cut & fill M 0.3375 -0.5025 L 0.3775 -0.4525 K 0.4475 -0.3525 J 0.5175 -0.3725 21 22 For the 2nd two blocks 1st unit 3rd unit J 296.32 296 16 I 295.79 295.6 H 295.17 295.01 G 294.58 294.5 F 293.95 293.88 23 Determination of Formation level Centroid level= Centroid point is H, 1&2 592.84 591 67 590.48 589.26 588.15 2952 4 295.24 Determination of Formation level Centroid level= Centroid porn: is H. 1&2 592 48 591.39 590 18 589.08 587.83 2950 96 295.096 J 295 74 295.54 1 295 54 295.34 H 295.34 295.14 G 295 14 294 94 F 294 94 294.74 1 2Detrmination of cut & fill Detrmination of cut & fill J 0.78 0.78 1 0.34 0.45 H •0.03 0.03 G •0.46 -0.36 F •0.74 -0.79 1 2 2nd unit 4th unit 587.02 585.56 5866 584.55 583.57 582.92 585.17 583.77 582.3 2923.64 581.42 2919 26 Determination of Formation level Centroid tevel= Centroid point is C. 1&2 292 364 Determination of Formation level Centroid level= Centroid point is C. 1&2 291 926 Detrmination of cut & fill Detrmination of cut & fill E 0.766 0.726 D 0.336 0.116 E 0.964 C 0.116 -0.294 0.984 D B -0.034 -0.724 0.354 0.564 -0.164 C A •0.844 -0.056 -0.026 B 1 2 -0.456 -0.666 A -0.606 -1.026 2 35th unit 7th unit Determination of Formation level Centroid level= Centroid point is H, 182 592.09 590.98 589.83 588.85 587 69 2949 44 294.944 Determination of Formation level Centroid level= Centroid point is H, 4&5 591.56 590.44 589.45 588.52 587.54 2947.51 294.751 Detrmination of cut & fill Detrmination of cut & fill J 0.716 0.686 I 0.356 0.336 J 0.679 0.579 H -0.034 -0 024 I 0.329 0.209 G -0.344 -0 294 H -0.031 -0.021 F -0.764 -0.634 G -0.301 -0.281 3 4 F -0.641 -0.521 4 5 6th unit 8th unit E 293.21 293.29 D 292 59 292.62 C 291.8 291.86 B 290.96 291.1 A 290.4 290.29 3 4 586 5 585.21 583.66 582.06 580.69 2918 12 Determination of Formation level 565 57 585.33 583 85 582 29 58069 2918 74 r•Centroid level= Centroid point is C. 1&2 291.812 Determination of Formation level Centroid level= Centroid point is C. 4&5 291.874 E 292.312 292.112 D 292.112 291.912 C 291.912 291.712 0 291.712 291.512 A 291 512 291.312 2 3 Dctrmination of cut & fill Detrmination of cut & fill E 0.898 1.178 D 0.478 0.708 E 0.916 1.106 C -0.112 0.148 0 0.446 0.736 B -0.752 -0.412 C -0 114 0.226 A -1.112 -1.022 B -0.674 -0.384 2 3 A -1.284 -0.974 4 5 9th unit 11th unit 590.91 589 81 588 93 588.1 587.33 2945 08 590.15 589.15 588.24 587 57 585.99 2942.1 Determination of Formation level Centroid level= Centroid point is H. 4&5 294.508 Determination of Formation level Centroid level= Centroid point is H, 687 294.21 J 294.71 294.51 I 294.51 294 31 H 294 31 294.11 G 294 11 293.91 F 293 91 293 71 6 7Detrmination of cut & fill Detrmination of cut & fill J 0.622 0.472 1 0.252 0.142 H 0.022 -0.108 G -0.238 -0.278 F -0 478 -0.408 15 6 10th unit 12th unit 586.39 585 39 584.05 582.46 580.9 2919 19 291.919 E 293.11 293 D 292 68 292.38 C 292.05 291.74 B 291.27 291.1 A 290.5 290.46 6 7 Determination of Formation level Centroid level= Centroid point is C, 5&6 Determination of Formation level Centroid level= Centroid point is C. 6A7 585.11 585.06 583.79 582.37 580.96 2918.29 291.829 Detrmination of cut & fill 0 861 0.891 Detrmination of cut & fill E D 0 491 0.661 C -0 019 0.231 B -0629 -0 349 A -1.219 -0 919 5 613th unit 15th unit Determination of Formation level Centroid level= Centroid point is H, 7&6 589.23 588.38 587.53 586.94 586.44 2938.52 293.852 Determination of Formation level Centroid level= Centroid point is H, 889 588.16 587 39 586.67 586 12 585.58 2933.92 293.392 Detrmination of cut & fill Detrmination of cut & fill J 0.518 0.208 I 0.248 0.028 H -0.012 -0.162 G -0.112 -0.252 F -0 162 -0 302 7 8 14th unit 16th unit E 293 292.57 D 292 38 292 C 291.74 291.34 B 291.1 290.76 A 290.46 290 12 7 8 585.57 584.38 583.08 581.86 580.58 2915 47 584 7 563.55 582.28 581.09 579.85 2911 47Determination of Formation level Centroid level= Centroid point is C, 7&8 291.547 Determination of Formation level Centroid level= Centroid point is C, 8&9 291 147 Detrmination of cut & fill Detrmination of cut & fill E 0.953 0.723 D 0.533 0.353 C 0 093 •0.107 B -0.347 -0.487 A -0.787 -0.927 7 8 17th unit 19th unit J 2938 293.24 I 293.41 292.82 H 293.08 292.44 G 292.82 292.24 F 292.53 291.89 9 10 Determination of Formation level Centroid level= Centroid point is H. 9&10 587.04 586.23 585.52 585.06 584.42 2928.27 292.827 586.454 586.054 585.654 585.254 584 854 2928 27 Determination of Formation level Centroid level= Centroid point is H. 10&11 585.74 584 97 584 24 58365 582 89 2921 49 292 149 585.098 584.698 584.293 583 898 583.498 2921.49Dctrmination of cut & fill Dctrmination of cut & fill J 0.473 0.113 I 0.283 -0.107 J 0.591 0.051 H 0.153 -0.287 I 0.371 -0.099 G 0.093 -0.287 H 0.191 -0.249 F 0.003 -0.437 G 0.191 -0.439 9 10 F 0 041 -0.649 10 11 18th unit 20th uni! E 292.13 291.4 D 291 55 290.92 C 29094 290.49 B 290.33 289.89 A 289.73 289.27 9 10 Determination of Formation level Centroid level= Centroid point is C, 9&10 583.53 582.47 581.43 580.22 579 2906.65 290.665 Determination of Formation level Centroid level= Centroid point is C, 9810 581.9 580.92 579 99 578 89 577.7 2899.4 289 94 E 291.165 290 965 0 290.965 290.765 E 290.44 290.24 C 290.765 290 565 D 290.24 290.04 B 290.565 290 365 C 290.04 A 290.365 289.84 .290.165 B 289.84 9 10 289.64 A 289.64 289.44 Detrmination of cut & fill 9 10 Detrmination of cut & fill E 0.96 0.26 D 0.68 -0.04 C 0 45 -0.34 B 0.05 -0.64 A -0 37 -1.01 3 1021th unit 23rd unit J 292.5 291.5 I 292.15 291.15 H 291.8 290.83 G 291.41 290.45 289.75 F 291 290 584 583 3 582 63 581.86 581 2912.79 291.279 J 291.5 290.5 1 291.15 290.05 H 290 83 G 290.45 289.35 11 12 F 290 288.95 12 13 Determination of Formation level Centroid level= Centroid point is H, 11&12 Determination of Formation level Centroid level= Centroid point is H, 12&13 582 581 2 580.58 579 8 578 95 2902.53 290.253 J 291.779 291.579 I 291.579 291.379 H 291.379 291.179 G 291.179 290.979 F 290.979 290.779 11 12 583.358 582.958 582.558 582.158 581.758 2912 79 J 290.753 290.553 I 290.553 290.353 H 290.353 290.153 G 290.153 | 289.953 F 289 953 289.753 12 13 581.305 580.905 580.506 580.106 579.706 2902 53 Detrmination of cut & fill Detrmination of cut & fill J 0.721 -0.079 I 0.571 -0.229 J 0.747 -0.053 H 0.421 -0.349 I 0.597 -0.303 G 0.231 -0.529 H 0 477 -0.403 F 0.021 -0.779 G 0.297 -0.603 11 12 F 0 047 0.803 12 13 22nd unit 24th unit E 290.5 D 580 579 578.04 577 575.93 2889 97 Determination of Formation level Centroid level= Centroid point is C. 11&12 289 5 290 289 E 269 5 C 289.5 288.54 288.5 D 289 B 289 288 288 C 288.54 A 288.43 287.5 287.57 B 288 11 12 287 A 287.5 286 51 12 13 288 997 Determination of Formation level Centroid level= Centroid point rs C. 12&13 576 577 576.11 575 574 01 2680 12 28S 012E 289.497 289.297 D 289.297 289.097 C 289.097 288.897 B 288.897 288.697 A 288.697 288 497 11 12 Detrmlnation of cut & fill Detrmlnation of cut & fill E 1.003 0.203 D 0.703 -0.097 E 0.988 0.188 C 0.403 -0.357 D 0.688 -0.112 B 0.103 -0.697 C 0.428 -0.342 A -0.267 -0.997 0 0.088 -0.712 11 12 A -0.212 -1.002 12 13 25th unit J 290.5 289.39 27th unit I 290.05 289 J 289.39 288 36 H 289.75 288.67 I 289 288 G 289.35 288.26 H 286.67 287.64 F 288 95 287.89 G 288.26 287.27 13 14 F 287.89 286.86 14 15 Determination of Formation level Centroid level= Centroid point is H. 12813 Determination of Formation level Centroid lcvel= Centroid point is H, 12813 J 289.681 289.481 1 289.481 289.281 J 288.634 288.434 H 289 281 289.081 G 289.081 288.881 F 288 881 288 681 12 13 579 89 579.05 578 42 577 61 576 84 2891.81 289 181 579.162 578 762 578.362 577.962 577 562 2891.81 1 288.434 288.234 H 288.234 288.034 G 288 034 287.834 F 287.834 287.634 12 13 577.75 577 576.31 575.53 574.75 2881.34 288.134 577.068 576.668 576.268 575.868 575.468 2881.34Detrmination of cut & fill Detrmination of cut & fill J 0.819 -0 091 I 0.569 -0.281 H 0.469 -0.411 G 0.269 •0.621 F 0.069 -0.791 12 13 26lh unit 28th unit E 288.5 287.5 O 288 287 C 287.57 286.57 B 287 286.06 A 286.51 285 56 13 14 Determination of Formation level Centroid levcl= Centroid point is C. 13814 576 575 574.14 573.06 572.07 2870.27 287 027 Determination of Formation level Centroid level= 574 573 572.14 571.17 570.19 2660 5 286 05 Centroid point is C. 13814 Detrmination of cut & fill Detrmination of cut & till E 0.973 0.173 D 0.673 -0.127 E 0.95 0 443 0 15 C -0.357 D 0.65 0.073 -0.15 B -0.667 C A -0.217 0.42 •0.967 -0.38 B 0 11 -0.64 12 13 A •0.19 -0.92 12 1329th unit 31 st unit J 288.36 287.32 I 288 286.93 H 287.64 286.59 G 287.27 286.22 F 286.86 285.82 15 16 Determination of Formation level Centroid level= Centroid point is H. 12&13 575.68 574.93 574.23 573.49 572.68 2871.01 287.101 575.002 574.602 574.202 573.802 573.402 2871.01 Determination of Formation level Centroid level= Centroid point is H, 12&13 J 287.601 287.401 I 287.401 287.201 J 286.54 286.34 H 287.201 287.001 I 286.34 286.14 G 287.001 286.801 H 286.14 285.94 F 286.801 286.601 G 285.94 285.74 12 13 F 285.74 285.54 12 13 573.61 572.79 572.09 571.36 570.55 2860.4 286.04 572.88 572.48 572.08 571.68 571.28 2860.4 Dctrmination of cut & fill Dctrmination of cut & fill J 0.759 -0.081 I 0.599 -0.271 J 0.78 -0.05 H 0.439 -0.411 I 0.59 -0.28 G 0.269 -0.581 H 0.45 -0.44 F 0.059 -0781 G 0.28 -0.6 . 12 13 F 0.08 -0.81 12 13 30lh unit 32nd unit E 286.5 285.42 D 286 285 C 285.57 284.67 0 285.11 284.17 A 284.63 283.72 15 16 571 92 571 570 24 569.28 568.35 2850.79 569 74 568 93 568.17 567 29 566 39 2840.52Determination of Formation level Centroid level= Centroid point is C, 13&14 285.079 Determination of Formation level Centroid level= Centroid point is C, 13&14 284.052 E 285.579 285.379 D 285.379 265.179 C 285.179 284.979 B 284.979 284.779 A 284.779 264 579 12 13 Dctrmination of cut & fill Dctrmination of cut & fill E 0921 0.041 D 0.621 -0.179 C 0.391 -0.309 B 0.131 -0 609 A -0.149 -0 859 12 13 33rd uni: 35th unit J 286.29 285.32 1 285.86 284.83 H 285 5 284.44 G 285.14 284 F 284.73 283.64 17 18 Determination of Formation level Centroid level= Centroid point rs H. 12&13 571 61 570 69 569 94 559 14 568 37 2849 75 284 975 570 75 570 35 569 95 569 55 569 15 2849 75 Determination of Formation level Centroid level= Centroid point is H. 12& 13 J 284.413 284 213 I 284.213 r 284 013 H 284.013 283 513 G 283.813 263 613 F 283 613 283 413 12 13 569 35 568 64 567 85 567 565.28 2839.13 283 913 568 526 568 226 567 826 567 426 567 026 2639 13Dctrmination of cut & fill Dctrmination of cut & fill J 0.815 0.045 I 0.585 -0.245 J 0.907 -0.173 H 0.425 •0.435 1 0.617 -0.203 G 0.265 -0.675 H 0 427 -0.403 F 0.055 -0.835 G 0.187 -0.613 12 13 F 0.027 -0.773 12 13 34th unit 36lh unit E 284.32 283.26 D 283.93 282.84 C 2283.5 282.44 B 283.12 282 A 28267 281.64 567.58 566.77 2565.94 565 12 564 31 4829 72 482 972 E 283.26 282 25 D 282.84 281.84 C 282.44 281.41 B 282 281 A 281.64 280.64 17 18 18 19 Determination of Formation level Centroid level= Centroid point is C, 13814 Determination of Formation level Centroid level= Centroid point is C. 13&14 565.51 564.68 563.85 563 562.28 2819.32 281.932 Dctrmination of cut & fill Dctrmination of cut & fill E 0.828 0.018 D 0.608 -0.192 C 0.408 -0.422 B 0.168 -0.632 A 0 008 -0.792 12 1337 th unit 39th unit J 284 04 282.88 I 283.61 282.73 H 283.41 282.14 G 283 282 F 282.64 281.64 19 20 Determination of Formation level Centroid level= Centroid point is H, 12&13 Determination of Formation level Centroid fevel= Centroid point is H, 12&13 J 283.329 283.129 1 283.129 282.929 H 282.929 282.729 G 282.729 282.529 F 282.529 282.329 12 13 566 92 566 54 565.55 565 564.28 2828.29 262.829 566.458 566 058 565.658 565 258 564.858 2828 29 564.75 564.33 563.4 562.84 562.14 2817 46 261 746 564 292 563.892 563.492 563.092 562.692 2817 46 Dctrmination of cut & fill Dctrmination of cut & fill J 0.711 -0.249 I 0.681 -0.199 H 0481 -0.589 G 0.271 -0.529 F 0 111 -0.689 12 13 38th unit 40th unit E 282.25 281.23 D 281.84 280.84 C 281.41 280.41 B 281 280.02 A 280 64 279 79 19 20 563.48 562 68 561 82 561.02 560.43 2809 43 561.34 560 59 559.81 559.15 558 7 2799 59Determinalion of Formation level Centroid level= Centroid point is C, 13814 280.943 Determination of Formation level Centroid level= Centroid point is C. 13814 279.959 E 281.443 281.243 D 281.243 281.043 C 281.043 280.843 B 200.843 280.643 A 280.643 280.443 12 13 Dctrmination of cut & fill Dctrmination of cut & fill E 0.807 -0.013 E 0.771 -0.149 D 0.597 -0.203 D 0.581 -0.309 C 0.367 -0.433 C 0.351 -0.459 B 0.157 -0.623 0 0.161 -0.529 A -0.003 -0.653 A 0.131 -0.549 12 13 12 13 41st unit 4 3rd unit J 281.87 280.78 J 280.78 279.74 I 281.6 280.5 I 280.5 279.5 H 281.26 280.18 H 280.18 279.16 G 280.84 279.81 G 279 81 278.84 F 280.5 279.43 F 279.43 278.54 21 22 22 23 Determination of Formation level Centroid lcvel= Centroid point is H, 12&13 Determination of Formation level Centroid level= Centroid point is H. 12813 J 281.177 280.977 J 280.977 280 148 1 280.777 279.948 1 H 280.777 280.577 279.948 279.748 H 279 748 G 280 577 280.377 F 280 377 280 177 12 13 562 65 562 1 561.44 560.65 559 93 2806 77 280.677 562 154 561.754 561 354 560 954 560 554 2606 77 279.548 G 279.548 279.348 F 279 348 279.148 12 13 560.52 560 559.34 558 65 557.97 2796 48 279.648 560.096 559.696 559.296 558 896 558.495 2796 4 8Detrmination of cut & fill Detrmination of cut & fill J 0.632 -0 208 I 0.552 -0.248 H 0.432 -0.338 G 0.262 -0.508 F 0.082 -0.608 12 13 42nd unit 44 th unit E 280.11 279.1 D 279.75 278.8 C 279 4 278.59 B 279 13 278.45 A 278.91 278.25 21 22 Determination of Formation level Centroid level= Centroid point is C. 13&14 559.21 558.55 557.99 557.56 557.16 2790.49 279.049 Determination of Formation level Centroid level- Centroid point is C. 13&14 557.35 556.88 556.52 556.26 555.91 2782 93 278 293 E 279.549 279.349 E 278.793 278.593 D 279.349 279.149 D 278.593 278.393 C 279.149 278 949 C 278 393 278 193 B 278 949 278.749 B 278.193 277 993 A 278.749 278.549 A 277.993 277.793 12 13 12 13 Detrmination of cut & fill Detrmination of cut & fill E 0.561 -0.249 D 0.401 -0.349 C 0.251 -0.359 B 0.181 -0.299 A 0.161 -0.299 12 13Q P O N M L K J I H G F E D C B A Hy Dx Hy.Dx 296.72 296,12 295.56 295 294,53 294.1 293.61 293.24 292.82 292.44 292.24 291.69 291.4 290.92 290.49 289.89 289.27 10 4980.24 475 2365614 296 295.4 294,84 294,25 293.78 293.25 292,83 292.5 292.15 291.8 291.41 291 290.5 290 289.5 289 288,43 11 4966.64 295.09 294.45 293.82 293.29 292.77 292.28 291.83 291.5 291.15 290.83 290.45 290 289.5 289 288,54 288 287.5 12 4950 294.02 293.43 292.64 292.32 291.82 291.3 290.64 290.5 290.05 289.75 289.35 28B.95 288.5 288 287,57 287 286.51 13 4932.75 293 292.42 291.84 291.33 290.82 290.36 289.5 289.39 289 288,67 288.26 287.69 287.5 287 286.57 286,06 285.56 14 4915.17 525 2607486 575 625 2846250 3082968.8 675 3317740 292 291.43 290.87 290.38 289.87 289.33 288.82 288.36 288 287.64 287.27 286.86 286.5 286 285.57 285.11 284.63 15 4898.64 725 3551514 291 290.45 289.89 289.39 288.87 288.33 287.82 287.32 286.93 286.59 286.22 285.82 285.42 285 284,67 284.17 283.72 16 4881.61 775 3783248 290 289.4 268.9 288.37 267.86 287.33 286,82 286.29 285.86 285.5 285.14 284,73 284.32 283.93 283.5 283.12 282.67 17 4863.74 825 4012586 288.73 288.21 287.69 287.17 286.72 286.25 285.6 285.32 284.83 284.44 284 283.64 283.26 282.84 282.44 282 281.64 18 4844.98 875 4239358 286.3 266 285.58 285.23 284.83 284.45 284,04 283.61 263.41 283 282.64 282.25 281.84 281.41 281 280.64 19 4823.16 925 4461423
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