AWASH VALLEY AUTHORITY ADDIS ABABA
**• •
MELKA SADI-AMIBARA PROPOSED IRRIGATION PROJECT
FEASIBILITY STUDY
VOL. I - HYDROLOGY AND CLIMATOLOGY
£ I TALCO NS Ul. T i Rome, July 1969
. X--CONTENTS
PART I -          GENERAL REPORT
PART 11 -       STUDIES AND SURVEYS
VOL. I - HYDROLOGY AND CLIMATOLOGY VOL. 2 - SOIL SCIENCE
VOL. 3 - GEOLOGY AND HYDROLOGY VOL. 4 - IRRIGATION ENGINEERING VOL. 5 - AGRICULTURE AND LIVESTOCK
PART in-
VOL. 6 - ECONOMIC AND FINANCIAL ASPECTS VOL 7     - SOCIOLOGICAL AND HEALTH ASPECTS OUTLINE OF THE PROJECTIMPERIAL ETHIOPIAN GOVERNMENT
awash valley authority
ADDIS ABABA
MELKA SADI-AMIBARA PROPOSED
IRRIGATION PROJECT
FEASIBILITY STUDY
PART II
STUDIES AND SURVEYS
VOI. 1 - HYDROLOGY AND CLIMATOLOGYCONTENTS
1.
2.
INTRODUCTION
CLIMATIC INVESTIGATIONS
2. 1 GENERAL
2. 2 AVAILABILITY OF DATA
2. 3 RAINFALL
2.3.1 Amount
2. 3. 2 Rainfall Intensity in the Study Area
2.4 TEMPERATURE
2. 5 MEAN RELATIVE HUMIDITY
2. 6 EVAPORATION
2. 7 RADIATION
2. 8 WIND SPEED
2. 9 CLIMATIC BALANCE (AFTER THORNTH- WAITE) OF THE STUDY AREA FOR IRRI
GATION PURPOSES
Page 1 3 3
3 4 4
7
7
9
10
1 1 11
3.       HYDROLOGIC INVESTIGATIONS
3. 1 GAUGING STATIONS
3. 2 PERIOD OF OBSERVATION
3.3 RUNOFF
4.       DESIGN FLOOD ESTIMATES
4. 1 FLOODS ON THE AWASH AT AWASH STATION
4. 1. 1 Maximum 24-Hour Flood: Q , 
(Fllller's Method)
M
max
4. 1.2 Maximum Peak Discharge: QjvlAX (FUller's Method)
12
15
15
15
16
23
23
23
254.           1. 3 Flood from Creager's Equation
41.4 Total Maximum Observed Runoff
Volume
4 2 FLOODS ON THE KESSEM AT AWARA MELKA 4.2.1       Maximum 24-Hour Flood: Qmax
(Fllller  s Method)
4.2.2       Maximum Peak Discharge: Q  AX
1
M
(FUller's Method)
4.2.3       Flood from Creager's Equation
4.2.4       Total Maximum Observed Runoff Volume
4. 3 FLOODS ON THE KEBENA AT THE AVA
STATION
4.3.1       Maximum 24-Hour Flood: Qmax
(FUller's Method)
4. 3. 2 Maximum Peak Discharge: Qj^aX
(FUller's Method)
4.3.3      Flood from Creager's Equation
4. 3. 4 Total Maximum Observed Runoff Volume
4. 4 FLOODS ON THE ARBA AT ARBA
4.4.1      Maximum 24-Hour Flood: Qmax
(FUller's Method)
4.4.2      Maximum Peak Discharge: QjtfA.X
4. 4. 3 Flood from Creager's Equation
4- 4. 4 Total Maximum Observed Runoff Volume
4. 5 FLOODS ON THE AWASH IN THE STUDY AREA
4. 5. 1 General
4. 5. 2 Floods on the Awash at Melka Sadi
4. 5. 3 Floods on the Awash at Melka Warar
4.   6  EVALUATION   OF   THE   ROUGHNESS   OF   THE AWASH IN THE STUDY AREA
4  ' 
MEAS^REMENTS AND WATER
5.    WATER AVAILABILITY1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
TABLES
MEAN MONTHLY RAINFALL - WONJI
MEAN MONTHLY RAINFALL - KOKA
MEAN MONTHLY RAINFALL - METEHARA
MEAN MONTHLY RAINFALL - SHENO
MEAN MONTHLY RAINFALL - AWARA MELKA
MEAN MONTHLY RAINFALL - AWASH STATION
MEAN MONTHLY RAINFALL - DEBRE BERHAN
MEAN MONTHLY RAINFALL - MELKA WARAR
CRITICAL RAINFALL AT MELKA WARAR
CRITICAL RAINFALL AT AWARA MELKA CRITICAL RAINFALL (MAXIMUM EVENTS)
MINIMUM MONTHLY TEMPERATURE («C) - WONJI MINIMUM MONTHLY TEMPERATURE (OC) - METEHARA MINIMUM MONTHLY TEMPERATURE (°C) - MELKA WARAR MINIMUM MONTHLY TEMPERATURE (°C) - DUBTI MAXIMUM MONTHLY TEMPERATURE (°C) - WONJI MAXIMUM MONTHLY TEMPERATURE (»C) - METEHARA MAXIMUM MONTHLY TEMPERATURE (o ) - MELKA WARAR
C
MAXIMUM MONTHLY TEMPERATURE (°C) - DUBTI
AVERAGE MONTHLY TEMPERATURE (°C) - WONJI21
- AVERAGE MONTHLY TEMPERATURE (o  ) - METEHARA
C
22
23
AVERAGE MONTHLY TEMPERATURE (°C) - MELKA WARAR AVERAGE MONTHLY TEMPERATURE(°C) - DUBTI
24            ABSOLUTE     MINIMUM     AND     MAXIMUM     MONTHLY     TEMPERA TURES (°C) - MELKA WARAR
25             MONTHLY RELATIVE HUMIDITY (%) - WONJI
26             MONTHLY RELATIVE HUMIDITY (%) - METEHARA
27             DECADIC RELATIVE HUMIDITY (%) - MELKA WARAR
28             MONTHLY RELATIVE HUMIDITY (%) - DUBTI
29 ■
MONTHLY EVAPORATION - WONJI
30 -
MONTHLY EVAPORATION - KOKA
31 -
MONTHLY EVAPORATION - METEHARA
32 -
MONTHLY EVAPORATION - MELKA WARAR
33 -
MONTHLY EVAPORATION - DUBTI
34 -
MEAN MONTHLY RADIATION - WONJI
35 -
MEAN MONTHLY RADIATION ■ METEHARA
36 -
MEAN MONTHLY RADIATION - MELKA WARAR
37 -
MEAN MONTHLY RADIATION - AWARA MELKA
38 -
MEAN MONTHLY RADLATION - DUBTI
39 -
WIND SPEED - WONJI
40 -
WIND SPEED - METEHARA41 -
WIND SPEED - MELKA WARAR
42 -                 WIND SPEED - DUBTI
43 -
44 -
MONTHLY VOLUMES OF THE AWASH RIVER AT KOKA DAM MONTHLY VOLUMES OF THE AWASH RIVER AT WONJI
45 - MONTHLY VOLUMES OF THE AWASH RIVER AT METEHARA
46      -           MONTHLY VOLUMES OF THE AWASH RIVER AT AWASH STATION (1962-1966)
47 -                 MONTHLY VOLUMES OF THE AWASH RIVER AT AWASH STATION (1966-1968)
48 -                 MONTHLY VOLUMES OF THE ARBA RIVER AT ARBA
49 -                MONTHLY VOLUMES OF THE AWASH RIVER AT MELKA SADI
50 -                MONTHLY VOLUMES OF THE KESSEM RIVER AT AWARA MELKA
51     -
MONTHLY VOLUMES OF THE KEBENA RIVER AT AVA
STATION
52 -
MONTHLY VOLUMES OF THE AWASH RIVER AT MELKA
WARAR
53     -
MONTHLY VOLUMES OF THE AWASH RIVER AT SILKILE
54 -
MONTHLY VOLUMES OF THE AWASH RIVER AT HERTALE
55 -
MONTHLY VOLUMES OF THE AWASH RIVER AT DUBTI
56 -
ANNUAL VOLUMES (AWASH. KESSEM AND KEBENA
RIVERS)
57 -
MONTHLY      VOLUMES      (AWASH,      ARBA,      KESSEM
AND
KEBENA
RIVERS)58
59
60
61
62
63
64
65
66
67
68
FLOOD ESTIMATES
MONTHLY     SEDIMENT     LOAD,     OF     THE     AWASH     AND     OF     THE KESSEM RIVERS (1965-1966)
MONTHLY     SEDIMENT     LOAD,     OF     THE     AWASH     AND     OF     THE KESSEM RIVERS (1966-1967)
WATER ANALYSIS AWASH AT AWASH STATION
WATER ANALYSIS KESSEM AT AWARA MELKA
WATER ANALYSIS KEBENA AT AVA STATION
FIELD WATER REQUIREMENTS
WATER REQUIREMENTS UPSTREAM OF AWASH STATION FIELD IRRIGATION REQUIREMENTS FOR 10-DAY PERIODS MAXIMUM REQUIREMENTS FOR EACH TEN-DAY PERIOD
COMPARISON BETWEEN IRRIGATION DEMANDS AND NATURAL FLOWS OF THE AWASH KESSEM AND KEBENA RIVERSFIGURES
6
1    - MEAN MONTHLY TEMPERATURE (°C) - GAUGING STATION: MELKA WARAR - OBSERVATION PERIOD 1965-1968 (1967 INC LOMPLE TE)
2    - MEAN MONTHLY RAINFALL (mm) - GAUGING STATION: MEL KA WARAR - OBSERVATION PERIOD 1965-1968 (1966 INCOM PLETE) - MEAN ANNUAL RAINFALL OF THE PERIOD (1966 NOT INCLUDED): 576. 2 mm
3    - METEOROLOGICAL AND HYDROLOGICAL NET WORK
4    - INDICATIVE TREND OF CRITICAL RAINFALL
5    - MEAN MONTHLY VOLUMES (1 0  cu. m. ) - AWASH RIVER - GAUGING STATION: AWASH STATION - CATCHMENT AREA BELOW KOKA DAM: 7. 300 sq. km - OBSERVATION PERIOD NOV. 1962 - OCT. 1968
6    - DISCHARGE DURATION CURVE AND ANNUAL HYDROLOGIC CHARACTERISTIC - AWASH RIVER - GAUGING STATION: AWASH STATION
7    - MONTHLY DURATION CURVE - AWASH RIVER - GAUGING STATION: AWASH STATION - OBSERVATION PERIOD NOV. 1962 - OCT. 1966
8    - MONTHLY DURATION CURVE - AWASH RIVER - GAUGING STATION: AWASH STATION - OBSERVATION PERIOD NOV. 1 962-OCT. 1966
9    - MONTHLY DURATION CURVE - AWASH RIVER - GAUGING STATION: AWASH STATION - OBSERVATION PERIOD NOV. 1962-OCT. 1966
0 - MONTHLY DURATION CURVE - AWASH RIVER - GAUGING
STATION: AWASH STATION - OBSERVATION PERIOD NOV 1962 OCT. 19662
b
f
I
<
11 -
V ‘1'
12 -
MONTHLY     DURATION     CURVE     -     AWASH     RIVER     .     GA STATION: AWASH STATION - OBSERVATION PEri0 D
OCT. 1966 
MONTHLY      DURATION      CURVE      -      AWASH      RIVER      GA STATION: AWASH STATION - OBSERVATION
196Z-OCT. 1966 
PLR10D ».•
13 -
14 -
15 -
16 -
17 -
18 -
MONTHLY DURATION CURVE  - AWASH RIVER - GAUGINc STATION: AWASH STATION - OBSERVATION PERIOD NOV 1962-OCT. 1966
MONTHLY DURATION CURVE  - AWASH RIVER - GAUGING STATION: AWASH STATION - OBSERVATION PERIOD NOV. 1962-OCT. 1966
MONTHLY DURATION CURVE - AWASH RIVER - GAUGING
STATION: AWASH STATION - OBSERVATION PERIOD NOV. 
1962-OCT. 1966
MONTHLY DURATION CURVE  - AWASH RIVER - GAUGING STATION: AWASH STATION - OBSERVATION PERIOD NOV. 1962-OCT. 1966
MONTHLY DURATION CURVE  - AWASH RIVER- GAUGING STATION: AWASH STATION - OBSERVATION PERIOD NOV. 1962-OCT. 1966
STATION:     AWAsiZstaVE       '     AWASH     RIVER     -     GAUGING j 962-oCt  j966 aTI°n . OBSERVATION PERIOD NOV.
19 -
BE LOW Koka?°
volumes
6
N; A^’Ash st , CU‘ /n- > ~  ™ASH RIVER -
A
XOV- 1 966-
CTO-r 1968        T
DAjM; 7  3
’ °0 so ,AFION ' CATCHMENT AR^
q ’krn ~ OBSERVATION PERIOD
20 -
°1SCHAR P rx
C       duraTion
A 'V ASH STAtT/
IC  ‘ AWh Rn AND ANNUAL HYDROID
SH RIVER - GAUGING STATION:
TION
/21
irrrxT v DURATION CURVE - AWASH RIVER - GAUGING
“tat™n awash station - observation period NOV. 1966-OCT. 1968
22
MONTHLY       DURATION       CURVE 
- AWASH RIVER - GAUGING
STATION: AWASH STATION - I966-OCT. 1968
OBSERVATION PERIOD NOV.
23
MONTHLY DURATION CURVE - AWASH RIVER - GAUGING
24
STATION: AWASH STATION - OBSERVATION PERIOD NOV.
1966-OCT. 1968
MONTHLY DURATION CURVE - AWASH RIVER - GAUGING
25
STATION: AWASH STATION - OBSERVATION PERIOD NOV. 
1966-OCT. 1968
MONTHLY DURATION CURVE - AWASH RIVER - GAUGING
26
STATION: AWASH STATION - OBSERVATION PERIOD NOV. 
1966-OCT. 1968
MONTHLY DURATION CURVE - AWASH RIVER - GAUGING
27
STATION: AWASH STATION - OBSERVATION PERIOD NOV. 
1966-OCT. 1968
MONTHLY DURATION CURVE - AWASH RIVER - GAUGING
STATION: AWASH STATION - OBSERVATION PERIOD NOV. 
1966-OCT. 1968
28
MONTHLY     DURATION     CURVE     -     AWASH     RIVER     -     GAUGING
29
STATION:      AWASH      STATION      -      OBSERVATION      PERIOD      NOV 1966-OCT. 1968
MONTHLY DURATION CURVE  - AWASH RIVER - GAUGING SIATION: AWASH STATION - OBSERVATION PERIOD NOV 1966-OCT. 1968
30
CURVE
 ■
AWASH RIVER
 - gauging
H66 OCT. 1,^“ STAT'ON ' OBSERVAT“»* PERIOD: NOV.31 - MONTHLY DURATION CURVE - AWASH RIVER - GAUGING STATION: AWASH STATION - OBSERVATION PERIOD NOV. 1966-OCT. 1968
32 - MONTHLY DURATION CURVE - AWASH RIVER - GAUGING STATION: AWASH STATION - OBSERVATION PERIOD NOV. 1966-OCT. 1968
33 -         DISCHARGE DURATION CURVE AND ANNUAL HYDROLOGIC CHARACTERISTIC - KESSEM RIVER
34 -         DISCHARGE DURATION CURVE AND ANNUAL HYDROLOGIC CHARACTERISTIC - KE BENA RIVER
35 -         PROBABLE MAXLMUM FLOODS FOR THE AWASH RIVER AT AWASH STATION (FULLER'S METHOD)
36 -         AWASH RIVER AT AWASH STATION FLOOD OF FEBRUARY 12th 1966
37 -        AWASH RIVER AT AWASH STATION - FLOOD OF SEPTEMBER 7th 1967
38 -        AWASH RIVER AT AWASH STATION - FLOOD OF APRIL 2 8th 1968
39 -         PROBABLE MAXIMUM FLOODS FOR THE KESSEM RIVER AT AWARA MELKA (FULLER'S METHOD)
40 -         PROBABLE MAXIMUM FLOODS FOR THE KEBENA RIVER AT A.V.A. GAUGING STATION (FULLER'S METHOD)
41 -         KEBENA RIVER AT A. V. A. GAUGING STATION - FLOOD OF AUGUST 2nd 1 962
42 -        KEBENA RIVER AT A. V. A. GAUGING STATION - FLOOD OF JULY 30th 1963
43 -       KEBENA RIVER AT A. V. A. GAUGING STATION - FLOOD OF AUGUST 31 th 196444  -        KE BENA RIVER at a. V. A. GAUGING STATION FLOOD OF NOVEMBER 7th 1965
45  -       KEBENA RIVER AT A. V. A. GAUGING STATION - FLOOD OF AUGUST 7th 1966
46  -
PROBABLE MAXIMUM FLOODS FOR THE AR BA RIVER AT ARBA (FULLER’S METHOD)
47  -       ARBA RIVER AT ARBA - FLOOD OF MAY 18th 1963
48  -       ARBA RIVER AT ARBA - FLOOD OF SEPTEMBER 1 6th 1964
49  -       MELKA - SADI GAUGING STATION (CROSS-SECTION)
50  -        MELKA WARAR GAUGING STATION (CROSS-SEC
TION)
51  -       CORRELATION BETWEEN ISTANTANEOUS DISCHARGES OF KO KA, WON JI AND AWASH STATION1.    INTRODUCTION
This volume deals with  the meteorological and  hydrological the Project.  The meteorological features of the Study  Area mediate surroundings are covered  in  the first part; all the a ta have been processed and the results presented here.
The second  part covers hydrology,  in  which  discharge data for the most significant sections on  the Awash,  the Arba,  the Kessem and  the Kebena are presented and discussed.
In view of the particular location of the Area to be cultivated, particu lar attention has been given to the study of the occasional floods, de spite the fact that only a small amount of basic data are available.
Subsequently, a comparison is made between the amount of water avail able and the irrigation water requirements of the Study Area, due con sideration being given to present or expected future water uses upstream.
The situation was analyzed using the "a posteriori” approach for a pe riod of six years. On the assumptions adopted, it ensues that only on three days over this period would it not have been possible to satisfy irrigation requirements completely.
The analysis also takes account of the need to ensure sufficient water downstream of the diversion to meet the needs of man and beast, while in no way compromising the existence of the aquatic fauna immediately below the Melka Warar weir.2  CLIMATIC INVESTIGATIONS
general
The Study Area lies between 09°00- and 09°4(T N and 40°00’ and 40°30' E. It extends in an irregular and elongated manner over the middle Awash Valley, along the right bank of the river section starting slightly upstream of the confluence with the Kessem and ending upstream of the Awash-Cocai confluence. Both the Cocai and the Kessem are left bank tributaries.
In keeping with most of the remaining territory of Ethiopia, the physical ambient of the Study Area differs mainly from other territories in similar latitudes in its relatively moder
ate temperatures, due to the elevation. The whole of Ethiopia, in fact, can be looked upon as an island from the point of view of temperature, within the great zone delimited by the two tropics where the highest temperatures in the world are re gistered. In the Study Area the mean annual temperature (Melka Warar station) is 25. 6°C (average of three years of observations). The coolest months are December and January, and the warmest is June (Fig. 1). The rainfall, liable to even considerable variations in amount from year to year, averaged 576 mm annually (Fig. 2) at the Melka Warar raingauge station during the period of observation (three years). AVAILABILITY OF DATA
The da,. peocee.ed „„e obtained ftom the foUow ng bod es
..
Awash Valley Authority (AVA)
-                    AeiaUon Depa„  e„, 
m
hwa Wo„ji and Metehara Sugar Estatej h q
„-4 -
The observations contained in the Italian Ministry of Foreign Affairs’ publication "Contributo alia climatologia dell’Etiopia", by A. Fantoli (Rome 1965) were also used.
It has been deemed advisable to extend the collection of climatic data to a considerably larger area than that of the Study Area for the following reasons:
To view the climate of the Study Area within a wider framework;
To attempt correlations with stations having similar climates and for which there is a greater number of years of observation available;
To define the limits within which the observations of an agronomic nature made in farms of the middle valley can be extrapolated to the Study Area.
It seemed thus advisable to refer to a certain range of meteo rological observations made in some of the stations shown in Fig. 3. The selected data cover the following climatic factors:
i)       Rainfall
ii)      Temperature
iii)     Relative humidity
iv)     Evaporation
v)      Radiation
vi)     Wind
2- 3 RAINFALL
2.   3. 1 Amount
Tables I -8 show the monthly and annual rainfall figures for the various raingauge stations considered. As previously stated, these stations are scattered over a considerably larger area than that of the District under study.FIG. 1
mean monthly temperature (°C)
GAUGING STATION : MELKA WARAR OBSERVATION PERIOD: 1965 - 1968 (1967 INCOMPLETE)
SOURCE
AGRICULTURAL RESEARCH
STATION, MELKA
N. 2 6957
1 T ALCOS SULTFIG. 2
MEAN MONTHLY RAINFALL (mm.)
GAUGING STATION : MELKA WARAR OBSERVATION PERIOD 1965 1968 ( 1966 INCOMPLETE I
MEAN ANNUAL RAINFALL OF THE PERIOD (1966 NOT INCLUDED 576 2 mm7Z
FIG. 3
AMD HYDROLOGICAL METEOROLOGICAL
MET   WORKWhen available, the 1st, 2nd and 3rd maximum 24-hour rainfall events (i. e. the maximum amount of rain falling for 24-hours consecutively during the year under consideration) are also
shown.
The highest rainfall occurs on the highlands of the water divide. The maximum annual rainfall was: Debre-Berhan: 1,434mm (1967) and Sheno: 1,434 mm (1 963).
Along the Awash Valley the maximum annual rainfall occurred as follows: at Wonji: 1, 1 48 mm (1966); at Awash Station the maximum annual rainfall was 899 mm (1968); at Melka Warar it was 678 mm (1967).
For the Mclka Warar Station, situated in the District, in ad
dition to the above figures, data on the daily and decadal rain
fall and the number of rainy days are given.
As already mentioned for the station at Melka Warar, there
have only been three complete years of observation. It is
not possible therefore to obtain acceptable refined figures, 
but the following observations can be made;
1)     Two characteristic periods of rainfall can be distinguished: one in spring, usually from the end of February to the end 
of April - commonly called short rains - and a second pe riod from July to August called long rains (for the three- year period of observation, during these two months the average rainfall was 253 mm compared with the total
annual rainfall of 576 mm).
These two months are of particular interest in that they coincide with a good part of the vegetative cycles of sum mer crops for which the most suitable sowing period from the bio-productive point of view falls approximately between mid-June and mid-July.
The present limited development of summer crops is caused by the brevity of the period of long rains which only lasts for 60 days.2)      The individual falls are normally not notable, and out of
a total of 68 events during the three years of observation, about 50% were under 5 mm. Moreover, these events
only account for an average of 81 mm out of the total
576 mm (see Table 8/1).
These short rains are certainly a direct contribution to 
the scarce irrigation of plants, but they undoubtedly help 
to keep the relative humidity of the area at a reasonable
level by tempering the dryness which in this savanna area
is usually very high.
3)      Finally, it is to be noted that there is a great variability 
of rains from one year to another and from one month 
to another. The three-year period 1965-67-68. for which the complete data are available, shows that against a mini mum fall of 398 mm in 1965, there was a fall of 799 mm in 
1967.
Regarding monthly rains, it is to be noted that during the dry months of December and January there were hardly any falls for several years, whereas in spring the short rains are extremely variable. This observation is con firmed by the distribution of rains obtained at Awash Sta tion during the 1937-1940 and 1962-1968 periods. On the other hand, the latter observations cannot be used to extend the observations made at Melka Warar since during the common period of observation at the two stations it is not possible to establish a definite correlation between the 2 series of data. A correlation with the stations at higher elevations has also been excluded since the rainfall regime is considerably modified by variations in elevation.
It is worthwhile, however, to consider the average value of rainfall in November, but it is of little interest for
•agronomic ends because it is too isolated from the months of greatest rainfall.
It can even be said that in the particular case of cotton crops, this can be a disturbing element in that it coincides with the early picking of the capsules. For this reason it
dvi sable not to anticipate sowing this plant too early.Rainfall Intensity in the Study -Area
For the stations that most concern the Study Area (Melka W^rar and Awara Melka) data were collected on the maximum rainfall intensity over 0. 25 h, 0. 5 h, 1 h, 1. 5 h, 2h, 6h, 12h and 24h
The relative figures are contained in Table 9 (Melka Warar) and Table 10 (Awara Melka). Table 11 contains the maxi mum events from Tables 9 and 10; the latter are also given in Fig. 4.
Two straight lines have been drawn. The lower one envelops the representative points of the events at Melka Warar, and the top one. parallel to the latter, has been drawn to take account of the maximum events recorded also in the area immediately outside the Study (Awara Melka), in view of the brevity of the period of observation. Adopting as the line showing the critical
rainfall the form
hj = 20 t h 2 = 30t
h = atn, the critical rainfall formulae arc: 0. 37
and
0. 37 
for the lower line and the top line respectively.
Considering the above-mentioned conservative assumption, it may be taken that, lacking more valid elements, the two lines can be used as a basis in calculating the rainfall coef ficient and for the design of the drainage network of the Study Area.
TEMPERATURE
Tables 12 to 15 give the figures for the minimum monthly temperatures (in ©C) at the various meteorological stations These figures represent the average values of the absolute ’ minimum daily temperatures in the months in question.- 8 -
The lowest monthly figures recorded during observations, were- at Wonji: 7. 0°C (December 1966); at Melka Warar:
12.4OC (December 1965); at Dubti: I 7. 0°C (December 1965). Decadic values are also provided for the Melka Warar Station,
Tables 1 6 to 19 give the figures for the maximum monthly temperatures (in ^C) at the various meteorological stations. 
These figures represent the average values of the absolute maximum daily temperatures in the month in question.
The highest monthly figures recorded during observations were:
at Dubti (370 m a. s. 1.): 41.5°C (June 1 965);
at Melka Warar (750 m a. s. 1. ): 36. 8°C (June 1 965); at Metehara (955 m a. s. 1. ): 37. 9°C (July 1 965); at Wonji (1,540 m a. s. 1. ): 31. 1<>C (March 1 964).
Decadic values are also provided for the Melka Warar Station.
Tables 20 to 23 give the figures of the average monthly tempera tures (in °C) at the same meteorological stations (Wonji, Mete hara, Melka Warar and Dubti). For the station of Melka Warar minimum and maximum absolute values are also provided. The former was taken at 06. 00 hours of the morning; the latter at
18 p. m.
The average temperature has been obtained by combining
Tmax 4- T min
2
where T max and Tmin are the absolute maximum temperature and the absolute minimum temperature respectively, recorded over the 24 hours.
The lowest monthly figures recorded were: at Wonji: 15. 6°C (December 1 967).
7h. Mhest monthly figures recorded were: at Dubti (3 70 m
•8- ■). 4. 7°C (May 1967); at Melka Warar: 30. 9°C (June 1 965).-- TIME (HOURS)-9 -
For the station at Melka Warar, on the other hand, for which the decadal values are also given, the average temperature is
to be understood as the arithmetic mean of the values
T ma X| g + T min^
2
where Tmaxjg is the temperature taken at 18. 00 hours and 
T min£ is the temperature recorded at 06. 00 hours.
It is to be noted that for the Station at Melka Warar, maximum temperatures are reached in June (an average of 29. 7°C). It
is during this month that the vegetative cycles of summer herba ceous crops begins. Where possible, it would be advisable to start sowing and transplanting towards the end of June so as to reduce the requirements for irrigation water, since this is the hottest month of the year and is without rainfall (see Table 24).
Finally, considering temperature and rainfall together, since the average annual rainfall is 57. 6 cm and the average tempera ture is 25. 6°C, the Kbppen ratio is 57. 6/25. 6 = 2. 25, that is to 9ay a value which is very close to that of the savanna which is 2. 00.
Average temperatures are usually above 20°C even during the winter months, and the minimum night temperatures rarely drop below 10°C. It is to be noted that all months of the year are favorable to crops, except when considering the ideal bio logical cycles for each individual crop.
It is to be noted that in May and June, photosynthesis in some plants (vegetables) may be affected by the high day tempera tures which, on the whole, are above 3 5°C.
MEAN RELATIVE HUMIDITY
Tables     25     to     28     show     the     mean     monthly     relative     humidity     figures, in %, at the same four stations considered for the temperature.- 10 -
The lowest monthly values recorded were:
at Metehara (955 m a. s. 1. ): 35. 0% (February 196 7) The highest monthly values recorded were:
- at Melka Warar (750 m a. s. 1. ): 71. 7% (February 1966).
The examination of the decadal values from the station at Melka Warar (see Table 27) shows that the relative humidity during the three-year period in question, drops to less than 50% in June and in the last 10 days in May. This period coin cides with the highest temperatures and with the total lack of rainfall. Moreover, June is also one of the most windy months of the year.
The dryness of the air during May and June is another aspect which characterizes this period as being unsuitable for the vegetative development of most of the crops.
2.6 EVAPORATION
Tables 29 to 33 show the monthly figures for evaporation 
(in mm) at the various stations.
The lowest figures recorded during observations were: at Koka (1, 592 m a. s.l.): 133.0 mm/month (August 1 965). 
rhe highest figures recorded during the observations were:
- at Melka Warar (750 m a. s. 1. ): 376. 0 mm/month (May 1965) .
at Metehara (955 m a. s. I. ): 347. 0 mm/month (December 1966) .
J• 11
For the station at Melka Warar, the highest evaporation figures are recorded in the period from March to July, which includes the hottest months Turc’s formula indicates that even the highest potential evapotranspiration coincides with the period from March to July (see Vol. 4, Irrigation Engineering, chapter Irrigation Parameters).
2.7 RADIATION
Tables     34     to     38     give     the     mean     monthly     figures     for     the     radiation in cal/sq. cm/day.
It is to be observed, however, that the values relative to the
station at Melka Warar are not reliable, since there is too 
great a difference with the values which can be calculated on 
the basis of the latitude and longitude of the area.
The     data     recorded    at    Awara    Melka    -    close    to    the    area    under study - which were collected during the two-year period 1963-
1964, and are indicated in the study conducted by FAO in 1965, on the Awash Valley. These values have been used with Turc’s formula in calculating the potential evapotranspiration and are indicated in the Irrigation Engineering volume in the chapter on Irrigation Parameters.
2^8 WIND SPEED
Tables 39 to 42 show the mean monthly wind speeds at the various observation stations.
The lowest figures recorded were:
at Dubti (370 m a. s. 1.): 0. 90 m/sec (February 1 965)
at Melka Warar (750 m a. s. I. ): 0. 90 m/sec (February 1966). 
7- 12 -
The highest figures recorded were:
at Wonji (1, 540 m a. s. 1. ): 4. 70 m/sec (January 1 967)
In particular, for the station at Melka Warar the wind is not
an important factor throughout the year - except for the 4 month period from June to September when the average daily wind sp« . 
f
is often over 2 m/sec.
This wind speed does not put a limit to crops nor to surface flood irrigation, but it does create an obstacle in the case of
spray irrigation.
CLIMATIC BALANCE (AFTER THORNTHWAITE) OF THE STUDY AREA FOR IRRIGATION PURPOSES
According to the Thornthwaite method of classification, from the irrigation point of view, the climate of Melka Warar is semi-arid having a water index of -37. 19, which qualifies the climate as semi-arid bordering on arid (an arid climate starts with an index more of -40). Indeed, in 11 months of the year the potential evapotranspiration (1) exceeds the relative rain fall, as can be seen from the following balance.
Water Balance for Climatic Clasgih ca tion (or Irrigation (mm)
Item
J
F
M
A
M
J
J
A
S
O
N
D
Year
Rainfall (mm) (1965-66-68)
Pot. evapotranspiration (mm)
Water deficit (mm)
Water surplus (mm)
------------- ------- —     ■
3
70
32
80
42     59         25     27   101                40      16     70         9 111    1 34     168   210   186             151    122     93       68
6?
48
64     75      143  1B J     85             111    106     23      59              968 ------- *------- ■*----- I------- 1-------  ____ >------ 1------ 1------- *-----—----- -
152 142
10
•
576
i.sjM'I
10
1
tQ Turc And H^*neY“Crlddle formulae the potential evapotranspiration reeul* ,,7 ‘ mm and 1986 mm respectively, (tec VoL 4. para, |. 2).
(I) The potential evapotranspiration E (in cm/monih) ia calculated using the following formal*
E■
1.6 b               ) a. where:
I■
a■
b.
hy ,h*,um •' 12• • (f »'■5,4 c ’ —-
cubic  function  of  I,  according  to  the a   .   675   •   I1    •   »0*’   -   771   .   I2    .   10* coefficient   depending   on   the   latitude.
In unit! of 30 days of 12 houra each.
expression:
7 ♦ I. 792 • I - IO*5 ♦ 0.49239
expressing the moan possible duration of aunUfW13 -
This balance supplies the three Thornthwaite climatic indices:
a) Moisture Index
b) Dryness Index
surplus x 1 00 1. 535 
deficit x 1 00 1, 535
=      0.65 = 63.05
c)      Overall Water Index = Moisture Index -0.6 Dryness Index = = 0. 65 - (0. 6 • 63. 06) = -37. 1 9.- 15 -
3  hydrologic investigations
e
GAUGING STATIONS
In view of the shortness of the study, it has not been possible
to set up new gauging stations, nor to make any discharge
measurements. Therefore the relative observations made by 
the existing stations have been utilized. For some of these
sections a fair number of data are available, while for others
the period of observation is too short, especially for those
situated in the Study Area (Melka Warar and Melka Sadi). Ob
servations in the latter stations were even suspended owing to 
the impossibility of finding permanent observers.
The     data     obtained     arc     relative     to     the     12     gauging     stations     shown in Fig. 3.
3,2              PERIOD OF OBSERVATION
The data obtained  in  the corresponding  periods of observation, together with  the source of the data,  are shown  below for each gauging station considered.
1. Awash at Koka Dam:
Flows taken from the daily data pro
vided by EELPA (relative to flows
through the turbines at Koka power
2. Awash at Wonji;
station, November 1961-July 1968). Daily flows (source AVA) relative
3- Awash at Metehara:
to the period June 1964-October 1968
Monthly flows (source FAO) relative
to the period November 1962-October
1964; daily flows (source AVA) for
the period November 1964-October
1968 (with break in February 1968).4 Awash at Awash Station: Daily flows (source AVA). for the
’ period November 1962-October 1968.
5. Arba at Arba:
Daily flows (source AVA) for the
period November 1962-October 1 965.
6.   Awash at Melka Sadi: Daily flows (source AVA) for the
period September 1 967-May 1968.
7.     Kessem at Awara Melka: Daily flows (source AVA) for the
period November 1963-October 1 968.
8.     Kebena at AVA Station; Daily flows (source AVA) for the
period November 1962-October 1968.
9.     Awash at Melka Warar: Daily flows (source AVA) for the
period June 1967-August 1968.
10.   Awash at Silkile:                  Daily flows (source AVA) for the period June 1967-August 1 968.
Awash at Hertale:                 Monthly flows (source FAO) for the period November 1 962-February 1 963. Daily flows (source AVA) for the
period March 1963-October 1 965 and November 1966-October 1 968.
12- Awash at Dubti:                      Monthly flows (source AVA) for the period November 1964-October 1 965.
RUNOFF
Tables 43-55 show the monthly flows at the various gauging sta tions. For the Awash Station, the total period of observation (Nov. 1962-Oct. 1968) has been divided into two separate pe riods because as from 1966. when the Awash-2 plant became operative there was a change in the running of the Koka hydro electric plant.Two distinct periodscan therefore be distinguished at Awash Station:
November 1962 to October 1966 (average discharge: 54. 33 cu. m/sec);
November 1966 to October 1968 (average discharge: 43. 56 cu. m/sec).
This two-year period was particularly severe for downstream
uses in that the lower call for water through the turbines enable
a build up of storage of about 300 x 1 ()6 cu. m in lake Koka during the first year (1966-1967), and during the second year (1967-1968) said lower requirements concided with a hydrologic year of re latively poor flows.
The daily data were processed for both these periods. Fig. 5 shows the mean monthly volumes in the Awash River at Awash Station during the period November 1962-October 1966. Fig. 6 shows the annual duration curve obtained by processing the daily data over the 4 years and also the annual characteristic hydro logic curve, i. e. the curve which links the average divertable discharge (Sy) with the maximum divertable discharge (Qy) at
a hypothetical diversion. The difference 0 - Oy between the module and the average divertable discharge corresponds to that portion of the flows in excess of the maximum divertable discharge Qy and which are lost downstream.
The unit adopted in the diagram is the average discharge of the observation period (Q - 54.33 cu. m/sec).
The average discharge (viz. the module) has a duration of 31 % which means that values lower than average are more frequent (69%) than those of above average (31%). Discharges with a du ration of 25% and 75% have values of 1.08 and 0. 69 of average respectively. Discharges with a duration of 100% are equal to 0. 22 of the module (viz. 11. 95 cu. m/sec). The characteristic hydrologic curve shows, for example, that corresponding to a maximum discharge equal to the module (viz. 54.33 cu. m/sec), the average divertable discharge would be 0. 80 of the module (43. 46 cu. m/sec). The missing 0. 20 of the total is the amount of the discharge in excess of 54. 33 cu. m/sec.- 18 -
The duration of the daily discharges in the various individual
mean months of the year were also calculated as shown in 
Figs. 7-18. Fig. 19 shows the mean monthly volumes for the
period November 1966-October 1968. Fig. 20 shows the annual duration curve for the Awash River at Awash Station, obtained 
by processing the daily data for the 2 hydrologic years from November 1966 to October 1968 and also the annual character istic hydrologic curve as explained above. The unit adopted is
the average discharge in the observation period (Q - 43.56 cu.m/sec).
The average discharge (viz. the module) has a duration of 30% which means that values lower than average are more frequent (70%) than those of above average (30%). Discharges with a duration of 25% and 75% have values of 1.20 and 0. 61 of the average respectively. Discharges with a duration of 100% are equal to 0. 29 of the module (viz. 12.63 cu. m/sec).
The duration of the daily discharges in the various individual mean months of the year for the period November 1966 to October 1968 were also calculated, as shown in Figs. 21-32. 
Fig. 33 shows the annual duration curve and the annual hydro logic characteristic for theKessem River at Awara Melka, ob tained by processing the daily data for the 5 hydrologic years of the observation period (November 1963-October 1968). The unit adopted is the average discharge of the observation period CO = 18. 7 cu.m/sec). The average discharge (viz. the module) has a duration of 19%, which means that values lower than average are more frequent (81%) than those of above average (19%). Discharges with a duration of 25% and 75% have values of 0. 65 and 0. 05 of the average, respectively.
Fig. 34 shows the annual duration curve and the annual hydro logic characteristic for the Kebena River at the AVA gauging station, obtained by processing the daily data for the 6 hydro logic years of the period of observation (November 1962-October
1968).
The unit adopted is the average discharge for the 6-year observa tion period (Q = 9.57 cu.m/sec). The average discharge (viz. the module) has a duration of 24%, which means that values low-FIG. 5
6
mean MONTHLY VOLUMES ( 10 cu.m. )
AWASH RIVER - GAUGING STATION : AWASH STATION CATCHMENT AREA BELOW KOKA DAM : 7300 sq. km
OBSERVATION PERIOO NOV. 1962 - OCT 1966
22Q39
1"
164.06 279 S3 22Q39 133 56
N. 26961
• T A I.CONSULTFIG. 6
DISCHARGE DURATION CURVE and annual hydrologic characteristic
awash RIVER - GAUGING STATION : AWASH STATION
-rzr—
AVERAGE
□IVERTABLE DISCHARGE
0.25        ■   :       050
—L-^4------ i------ r -7—TFu - ~
(♦> THE UNIT ADOPTED IS THE AVERacf n
6962 ° = 54'33
~:
F THE OBSERVATION PERIOD : NOV. 1962-OCT 1 966DISCHARGE
FIG. 7
MONTHLY DURATION CURVE
AWASH RIVER - GAUGING STATION : AWASH STATION OBSERVATION PERIOD NOV. 1962 -OCT 1966
B
THE UNIT ADOPTED IS THE AVERAGE .
THE ll E R1OD
41 6 8 cu mZsecI
No 26963
50              60
OF TIME
DURATIONUI5CHARGE
FIG. 8
MONTHLY DURATION CURVE
AWASH RIVER - GAUGING STATION : AWASH STATION OBSERVATION PERIOD NOV. 1962 - OCT 1966
,F Li -
THE  UNIT  ADOPTED  IS  THE  AVERAGE
discharge
MONTHS OF
OEJ-1 HE/FEBRUARY
THE PERIOD
ia=46.62cu.mZsec
No 26964
OF TIME
— DURATIONFIG 9
monthly duration curve
awash RIVER - GAUGING STATION : AWASH STATION OBSERVATION PERIOD NOV 1962 - OCT 1966
MA ROM
THE
UNIT ADOPTED IS;THE-AVERAGE
DISCHARGE OF THE
■■'■'MARCH;
MONTHS     OF     THE     PERIOD [Q= 44.22 cu m/secl.
No 26965
7. OF TIME
D-*~- DURATION
J r \LCO%-M'l 1FIG. 10
MONTHLY DURATION CURVE
AWASH RIVER - GAUGING STATION : AWASH STATION OBSERVATION PERIOD NOV. 1962 - OCT 1966UlbLHAKUt
FIG. 11
MONTHLY DURATION CURVE
AWASH RIVER - GAUGING STATION : AWASH STATION OBSERVATION PERIOD NOV 1962 - OCT 1966MONTHLY DURATION CURVE
AWASH RIVER - GAUGING STATION : AWASH STATION OBSERVATION PERIOD NOV. 1962 - OCT. 1966
JUNY
UNIT ADOPTED IS THE AVERAGE DISCHARGE OF THE
months or the perioo
iH;•
•
-o SO
::u
lijil
No 26968
OF TIME
DURATIONFIG. 13
MONTHLY DURATION CURVE
AWASH RIVER - GAUGING STATION : AWASH STATION OBSERVATION PERIOD NOV. 1962 - OCT. 1966
__ JULY- lip
JHE1UNIT ADOPTED IS.THE AVERAGE DISCHARGE OF THE JULY
MONTHS OFTHE PERIOD.
2'&cuJrn/secl
I
60              70
No 26969
7. OF TIME
0*- DURATION
100
I I AI.CONSUL1UlbUMAKUt
MONTHLY DURATION CURVE
AWASH RIVER - GAUGING STATION : AWASH STATION
OBSERVATION PERIOO NOV 1962 - OCT 1966FIG. 15
MONTHLY duration c^e
■
poo
11?
st
■-
...
THE UNIT ADOPTED IS
THE AVERAGE
' DISCHARGE. OF THE •
i months OF THE :RER
/Q = a5 03 Cu -n/     )
5eC
,
50
60
70
. OF TIME
No 26971
-^-durat
ionMONTHLY DURATION CURVE
AWASH RIVER - GAUGING STATION : AWASH STATION OBSERVATION PERIOD NOV 1962 - OCT 1966
OCTOBER
UNIT ADOPTED IS THE AVERA’GE
IE OCTOBER
MONTHS
(OxZ.9 86
PERIOD
7. OF TIME
I T M. < O S S L- L T
No 26972
0 -w— DURATIONmonthly duration curve
AWASH RIVER " GAUGING STATION : AW OBSERVATION PERIOD NOV 1962 - OCT. 19
NOVEMBER
I
THE  UNIT  ADOPTED  IS  THE  AVERAGE DISCHARGE OF THE NOVEMBER MONTHS OF THE PERIOD
I Qs36.11 cu.m/stc)
I
20                30                40                50                SO               70                OO               SO               100
7. OF TIME
D DURATION
I I XL l osDISCHARGE
FIG. 18
MONTHLY DURATION CURVE
awash RIVER - GAUGING STATION : AWASH STATION OBSERVATION PERIOD: NOV 1962 - OCT. 1966
DECEMBER
THE UNIT ADOPTED: IS THE AVERAGE DISCHARGE OF I HE DECEMBER
MONTHS OF THE
PERIOD
(Qm 26.78 cu.m/sec)
No 2697A
7. OF TIME
D*-DURATIONFIG. 19
MEAN
awash river -
CATCHMENT AREA
monthly volumes ( 10 <=u-
gauging STATION i awash station
BELOW KONA CAM T 7300 M
PERIOD NOV 1966 -oct 1968
IT
!• 26975FIG. 20
discharge duration curve and
annual hydrologic characteristic
AWASH RIVER - GAUGING STATION : AWASH STATION
THE  UNIT  ADOPTED  IS  THE  AVERAGE  OF  THE  OBSERVATION  PERIOD:  NOV.  1966-OCT.  I960 Q = 43.56 cu.m/stc
6
I ULCONSl LTFIG. 21
MONTHLY DURATION CURVE
AWASH RIVER - GAUGING STATION : AWASH STATION OBSERVATION PERIOD NOV 1966 -OCT 1968
JANUARY—
i. _..
THE UNITA
•DISCHARGE OF THE MONTHS    Of-THE    PERIOD (■Q = 25.33cu.rn/sBcl . I —•
;
No 26977
50              W
OF TIME
— DURATIONFIG.22
MONTHLY DURATION CURVE
AWASH RIVER - GAUGING STATION : AWASH STATION OBSERVATION PERIOD: NOV. 1966 - OCT. 1968
FEBRUARY
-THE UNIT ADOPTE
iiiaisaiiMreEiiaE 1
*-------------
» 10
No26978
IT ALCON SULT !FIG. 23
monthly duration curve
awash RIVER - GAUGING STATION : AWASH STATION OBSERVATION PERIOD : NOV 1965 - OCT. I960
MARCH
IN iS-O
UNIT ADOPTED IS
....
discharge OF THE MONTHS OF THE PERIOD
THE-AVERAGE
MARCH
nt/sec IFIG. 24
MONTHLY DURATION CURVE
AWASH RIVER - GAUGING STATION : AWASH STATION
OBSERVATION PERIOD. NOV 1966-OCT. 1968
DURATION
i ’TALCONSVLTFIG. 25
MONTHLY DURATION CURVE AWASH RIVER - GAUGING STATION : AWASH STATION
OBSERVATION PERIOD NOV 1966 - OCT 1968
MAY
DISCHARGE    OF    THE    MAY MONTHS OF THE PERIOD
“T------------ ---------
50                $0
OF TIME
DURATIONmonthly duration curve
awash RIVER - GAUGING STATION : AWASH STATION
OBSERVATION PERIOD : NOV 1966 -OCT. USE
o 26982
OF TIME
I talc: ON SUIT
DDURATIONDISCHARGE
FIG. 27
MONTHLY DURATION CURVE
AWASH RIVER - GAUGING STATION : AWASH STATION OBSERVATION PERIOD- NOV 1966 -OCT. 19G8FIG. 20
MONTHLY DURATION CURVE AWASH RIVER - GAUGING STATION : AWASH STATION
OBSERVATION PERIOD NOV 1966 - OCT. T968
AUGUST
:
: I
. 
■■
-TRE UNIT ADOPTED (S--TREAVERAGE DISCHARGE-OF THE AUGUST
MONTHS
(0=77,77
0FFIG.2
MONTHLY DURATION CURVE
AWASH RIVE a - GAUGING STATION : AWASH STATION OBSERVATION PERIOD NOV >966 - OCT 1966FIG. 30
MONTHLY DURATION CURVE
AWASH RIVER - GAUGING STATION AWASH STATION OBSERVATION PERIOD - NOV 1966 - OCT 196*
OCTOBER-
— *
THE UNIT ADOPTED IS.THE AVERAGE DDIISSCCHHAARRGGEE OOFF TTHHEE OOCCTTOOBBEERR MONTHS OF THE PERIOD
!!    it!:'
1 ri
FF Li:i
*■ <!;■"!
- L30
cu.m./secl
fin ~: '■ ________________ ,__ ■-
:■
1
■■ !■ 'rii
: !1
. 4 T; ;r . ::j
i •'*?
■;
A i.-r ■
:i
- 1,00
... 1
■ ■ - «.
■1
r
1
■ J -r
•
; . — ■ - ■ H
-
11
r■-
L._
r--
1
ow 25965
D DURATION
I r 4 I r o .s 5 (. l 1: DISCHARGE
MONTHLY DURATION CURVE
AWASH RIVER - GAUGING STATION : AWASH STATION OBSERVATION PERIOD - NOV 1965 -OCT. I960
THE   UNIT   ADOPTED   IS   THE   AVERAGE DISCHARGE-OF THE (NOVEMBER MONTHS OF THE PERIOD r
(0 = 39 SO cu.m/sec)DISCHARGE
FIG. 32
MONTHLY DURATION CURVE
AWASH RIVER - GAUGING STATION : AWASH STATION
OBSERVATION PERIOD NOV 1966 - OCT. 1968
. 0.50
J
♦ — I H
T-
' "*'T
No 2G90B
40               SO              £0
7. OF TIME
DURATIONDISCHARGE DURATION CURVE AND
ANNUAL HYDROLOGIC CHARACTERISTIC
KESSEM RIVER
F1G.33
THE   UNIT   AOOPTED   IS   THE   AVERAGE   DISCHARGE   OF   THE   OBSERVATION   PERIOD NOV 1963 - OCT. 1969                  Q 1B.7 cj n.TicDISCHARGE DURATION CURVE AND ANNUAL HYDROLOGIC CHARACTERISTIC
FIG.34
KEBENA RIVER
GAUGING STATION OF AYA.
average diverta
pit DISCHARGE
o.so
k
1
L-l-j
f - • i < n * z*
;‘l: ■ I
- h !• ;
•
i-H.
TZLi:' ri"-
’J-b t
i
i
— ■' ba
-1.
DURATION
■''0F time J
days o
the unit adopted in the average discharge NOY 1952 - OCT. 1968 Q 9,57 cu. m/l.c
of the observation period;
• TAtcnNsi'i y- 19 -
er than average are more frequent (76%) than those of above
average (24%). Discharges with a duration of 50% and 75%
have values of 0. 38 and 0. 1 5 of the average, respectively.
Table 56*  summarizing  the annual flows,  gives the following
average values for the various gauging stations:
SUlioa
Pc rlod
(HrdraLoflc r«*r. (romNoT.
to OcL )
Aver«|* Annas l Flow
(ID* ttf. m)
Mak*
,l!             at Wonji
ri           at MelehJf*
*•       at Await Station
Fi       H     H          <•
Ktilim »t Awipi
KrbiM at A VA                     station Awilh al Hnrlal*
(6 y»aT»)
1445” I9ft8: (J T«ara}
1962-1968:             yafcri)
1 <?62- 194ft:    (4 year*) 1964-1963:        (2 yian)
1963-196(1;       (5
1962-1968:        [6 yvatn)
I96t’l9tl [mji La L96*/66h
(ft yrtri)
I.014 9
1.219. 7
1.lift.4
1, 713. ft
I. 173.7
ft 90. 2
301.3
2, 227.4
It must first and foremost be noted that the values of the average annual flows are,  at all the stations,  lower than those considered as "normal" values in the FAO Report.
Furthermore, for the stations at Koka, Wonji, Metehara, and
Awash Station, there is a noteworthy downswing in the annual
flows as from the 1966/1967 hydrologic year. This can be put
down to the coming into operation of the Awash-2 plant. In or
der to calculate future uses, therefore, account must be taken
of this drop, as also of the consequences of the Awaah-3 plant's coming into operation. Going on to examine the monthly (lows
at the individual stations for the various hydrologic years, it is noted (see Table 57) that:
i) The monthly flows at Wonji are always higher (except in two
cases: June and December 1 965 - although the latter value
is doubtful) than those flowing through the Koka Dam turbines, by a quantity which bears out the hypothesis that, in addition to the amounts from the middle Koka-Wonji basin, and the known contribution of the warm springs there is a further not very well identified amount (which could however be
identified with the 11
 returns-to-bed’  of the presumed losses
1
from lake Koka). At the end of the ”Meki Diversion Scheme ’
1
project, this hypothesis can be borne out or rejected.- 20
ii) By comparing the monthly flows of Koka and Wonji with those of the stations further downstream (Metehara and Awash Sta tion), it is noted that for several months the flow* of the Metehara and Awash Station are smaller than those of Wonji. The above differences are more noteworthy in the months when there is zero or scanty rainfall (sec 1966-1^67). In this year the smaller flow at Awash Station than at Wonji in the months from November to June amount fd to l|4.Jxi0 cu m
6
In the year 1967/1968 the smaller flow at the Awash Station section than at Wonji was equal to 71. 6 x 10^ cu. m. during the whole year (l).
sit) In order to evaluate the flows usable for irrigation purpose* in the areas of Mrtka Sadi (upstream of the confluences of the Awash with the K^«?em and the Kebena. both left* bank tri bat .a ries) and of Melka Warar (downstream of the above confluences), rhe following considerations may be made
Since there are practically r.o observations of absolute reliability and duration, (no: even one year), the avail able flows at the Me [ka Sadi section (first weir) can be considered as equal to those a  Awash Station. In fact, 
e
there do not .ppea* to be any considerable variations tn the flows between the two secfioM the contribution of the only tributary of any sue. the Ar ba. on the rsgh! bank. is quite modest 10 cu m sec on average in
1963-1964 with a dr. bed for 5 morphs). This although the data shown in Table 5 7 indicate i considerably great er flow jt Me Ik j Sadi than it Awash Station daring the 7 months of observation from November J 967 ro May 
96A In f ebr-aary on the other hand the flow is small* er It is however stressed that these data are hardly reliable ar*d they h-ve been quoted merely for purpose* of infortn-i1aon
(i) In the FAO Study the looses between the Wonji i nd Awash Station sections were assessed «e equal to 140x ! (ft cu.rn p^r year, thus Subdivided stmosfahaetr i * 
. • i»n los«r*For the Melka Wnrar section (second weir) there are observations available which, as above, are not very reliable, and it is thus considered advisable not to take them into .account. Therefore, in the calculation of the water available at this section and the subsequent diver sion - which, it is to be noted, must be considered .19 flowing water since the reservoir created by the back water of the weir is very modest in size, and if any thing likely to effect daily regulation of the discharges - it is considered best to use only the daily data, duly processed, separately for the Awash Station on the Awash, the Awara Melka section on the Kessem and the AVA station on the Kebena.
It Is however immediately noted that the contribution of the two tributaries, the Kessem and the Kebena. is limit ed by their regime, and this characteristic appears
very clearly from the duration curves shown in Figs2 5
Ft CWS ON FHF
\ F XSfF \ FfON
4 l | Mfljtxmurn 44-Wtvir JFtcwd Qwaa i F il>--~ i Method)
t
r
fh# dtiiy vilunn rtf rh<* inmul j'IikwI* fl ■* 4FiM!e*t t< n*ir. <*r rirhsr th* manimum th*
r<*
liilv dig* haeg*
*iUii*« ah«*rvm| hi i
-*v i-dm* m ■ V twji*i * ' Vn»‘
Station during th* I :)6 I : Ihd period har* W<ti if«d '
h# mutimum iIihmI
th* t&til ■ it^hm«nk tatm mr i
4t tfioii. hu! ipMlptiRi 'hikre k« ' h«j ^04 » P • ■ n r >
■I'        •*
*      ■<  * * > «■) uv
>.    . -
1*1 -vhl.h Ihv
IF*
th.|w i ri hrf t it,- idrtHivn* k»f th* V * % jh JutiOfh ■. „ 
i*wi
»
.   - L,_, t *
h* tfi
F«411) r ■"’.•HI
■ I 1 \ fH M.ji T* * ■.-(?- V
i*
r*- 114
I 4. I fO I I 4 M ' Irttf WCTt
given he low (or ifeuiN'm* (tuvMif irid 1^44 m _j*> J *
t>-**4*< d klfeBir M>t«M I .“uni ’ h« VV \ Vr 1 1 vte -:} *
Hu«l
tv nn ««
>H r«-h ,*»- lb*
*   -g - ai * tU !
k‘
*   •*♦     ■#« Vie iMn ■ *
«M* •’♦* vMeiHiKl Ur
;«rg lh—-* li*> h*<-g« U1*<
4 dNT<3           tit •*.
r# ru*< * ♦
UC<1 llWl l
-in** r<4 Ma* ;•!><
41 tCuMn et*A*i?-j| J!J >-e t‘
gvj? * e*J I*
*-*• w*-n «*i^a oiw ** * u « 4.
»W
*           . >.►
"'*.
• »> *G?‘g .-* S.r .*»* /J r . w -. ;■ «kttn4- 24
Year
Month
Day
Flow
(cu, m)
Equal to Discharge
(cu. m/isc )
1963
1964
1965
1966
1967
1968
Auguet
August
5eplcmbe r September Sc pt e mb r r
April
IZ
7(a)
16
15
8
28
25. 328,000
24,897,306
13.284,000
13,812.652
15, 128. 816
17, 858. 880
270
288
154
160
175
207
(a) Regarding the maximum daily flow in 1964. the August I Oth value (IS. 668. 408 cu.m) has been Set aside for the following reasons:
-     On analyzing the chronological succession of daily (low values for the event in question - as shown in the AVA Bulletin - the trend of the flood wave appears very irregular.
-     This flow equates with an average discharge of 447 cu. m/itc which is even greater than the peak diacharges on the same day (4 35 cu.m/i»c according to AVA).
In view of thia, the figure of 36. 668. 408 cu. m haa been reduced to 1 0, 668. 408 while the Au gust 7 figure of 24. 897, 306 hae been taken for the maximum dally flow.
Utilizing FUller's method for predicting uncommon events, a straight line having the equation:
Qmax = 207 + 154 log T
is obtained (Fig. 35).JYom this the following values for 24-hour floods of 10-year, 100-year and 1, 000-year frequency are derived:
QmaxlO “ 361 cu. m/sec
QmaxlOO “ 515 cu. m/sec
QmaxhOOO = 669 cu. m/sec
The 1, 000-year discharge value (669 cu. m/sec) is 2. 3 times the maximum observed figure (288 cu. m/sec).
It should be noted that, in general, FUller’s method normally entails the examination and processing of a great number of d<±ta. However, considering that the representative points ofTIME (IN YEARS)
FIG. 35
PROBABLE MAXIMUM FLOODS FOR THE AWASH RIVER AT AWASH STATION (FULLER’S METHOD)- 25 -
the events processed here lie nicely along the "FtlUer straight line11 and that more valid methods of investigation are not avail able (considering the limited nature of the observations) it can be taken that the results are reasonably reliable.
4 I. 2 Maximum Peak Discharge:
(FUller  s Method)
1
The    peak    discharge    values    of    the    annual    floods    have    been    process ed to arrive at the maximum peak discharge (QWAV.)-
It should be noted that not all the flood events coincide, in time, with the maximum values of the daily discharges processed above. To understand why this is so, suffice it to remember that the daily discharge values refer: to the average of the discharges through a given section during the 24 hours of a calendar day. ThiB may lead to knowledge of the event being falsified. Indeed if, for example, a flood starts at 12 noon on a given day and fin ishes at 12 noon the following day, the total volume which flows in the 24 consecutive hours appears to be divided over the two days. As a result, the size of the event may be undervalued,
and it may even be classed as being smaller than some other minor event which occurred, however, during one given calendar
day.
Having made this clear, the maximum peak discharges for the 1963-1968 period are given below:
Feature* of Maximum Peak Flood
Year
Man th
D<y
( °MAX    - "V
Diaeharge
Ctt
Stage height
(h Ln m)
>963
>965
1967
1966
Auguet
August
September
February
September
April
12
7
16
12
7
21
110
4J5
194
311
210
528
3.82
4.10
2.75
3.50
2. S5
4. 60The values given above refer to the period after the r
came into operation, and as noted earlier, this exert
able routing effect on the 11,270 sq. km basin
8  * c°nai<ie
r
Indeed, it should be noted that in the days immediate1
flood events at Awash Station the maximum dischar * Pr€CedinI
Koka Dam sluices were as follows:
^      the
rorn
Year
Month
Day
Flo*
(cu. m)
Dlacharge
(cu. rn/eec)
—
—
1963
1964
1965
1966
1967
1948
Aufuat
Aufuat
September Febrva ry September
April
9
6
10
12
5
27
2,754,000
3.6JI.OOO
260. 000
4,761. 000
2.128.000
3, 03S. 000
31.9
42. 0
49. 3
55. 1
24.6
35.2
It can be seen from these figures that the influence of t e* above the Koka  Dam is negligible in the case of the event# ed at the Awash Station.  Thus the whole of the flood flows ured at this section can be assumed to  derive solely  from basin below Koka (7, 300 sq. km). The trends of the st* 
for the maximum floods recorded in 1 966. 1967 and 19 in Figs. 36, 37 and 38.
s ho**
Following Fliller’s method for calculating the 10-ycar’ ynade and 1,000-year events, and bearing in mind the cotn^
in para 4. 1.1, the appropriate line is shown on Fig equation of this line is:
Q MAX = 350 + 275 log T
ioo-yeaf
th* foll
OWlng
 maximum
peaR di8charges.-
0  /'ar frequency qMax]0 =
1.000 =
year frequency 
625
900
CU.
j 000 = j, I 75FEBRUARY
REPRODUCTION OF THE ORIGINAL
FROM A.V.A
G 36E669J
SEPTEMBER
REPRODUCTION OF THE ORIGINAL
FROM AV AAWASH RIVER AT AWASH STATION
FLOOD OF APRIL 28th 1968
APRIL
REPRODUCTION OF THE ORIGINAL FROM AVA.
FIG 38• 27 -
From the foregoing,  it ensues that the values for the 10-year. 100-year and 1,  000-year floods are respectively  1.2,  1.7  and 2,  2  times the value of the maximum event recorded in the six year observations (528 cu.m/sec).
4 j 3 Flood from Creager's Equation
By    examining    a    great    number    of    floods    observed    throughout    the world', Creager has arrived at a formula which may be written
as:
^MAX
%1AX
A
. „ A (0. 894A'°- °48) - 1
= 46. C. A. 
where:
=     flood     discharge     in     cusecs/square     mile = catchment area in square miles
C                  = Creager's coefficient.
Values of C in these units may vary depending on the climate
and geomorphology. The values obtained with Creager's for
mula represent the maximum probable flood with no frequency
factor implied.
For the Awash River at Awash Station (area = 7. 300 sq. km)
Creager's equation with C = 10 gives:
^Ma_X     - 235 liters/sec/sq. km
^MAX        = 1* 715 cu.m/sec
Total     Maximum Observed Runoff Volume
A    characteristic    feature    of    the    study    of    flood    events    is    the    total volume of flow between the beginning and the end of the event.Not having available the original charts from the recorder the daily flows (taken from the AVA Bulletins) have bee  su
n
med for the events studied earlier. The main flows of a num
ber of consecutive days calculated in this manner are:
—
Year
Month
Dayo
Flow
6
(IO co, mj
1963
1964
1965
1966
1967
1966
August
August
September
Septembe r
September
April
iOlh to 14th (5 days)
6th to 1 0th (5 days)
16th to 17th (2 days)
14th lo 16th (J daya)
6th to 9th (4 daya)
Z5th to 29th (5 daya)
95.6
82. a
20. 6
38. 7
53.7
68.5
This shows that the event involving the greatest total flow was the one between August 10 and 14, 1963, when 95. 6 million cu.m passed in 5 days. As seen earlier the maximum average dis charge occurred on August 10th with 288 cu.m/scc.
FLOODSONTHE KESSEM AT AWARA MELKA
Maximum 24-Hour Flood: Qmax (EUller's Method)
The area of the basin above Awara Melka Gauging Station i® 3, 135 sq. km which lies a fair way upstream of the point wher the Kesscm joins the Awash.
According to the AVA Bulletins, the maximum daily flows are
as follows:
Tear
Mralii
Day
<- rto-
(cu. m)
Iqual la DlecMrga
|cu. m/aec)
1964
1965
1466
1967
I9M
Auguci
Septcmtee r
Avgoat
Awguat
Awguei
1)
I
16
22
>
20. Tit. 200
IT. 71). 000
4>. >60. 000
>2.256.000
• J. 200. coo
240. 5
205 0
52* 0
*75. 0
SOO 0
—- 29 ,
It should be noted that for the months of July. August and September 1966 and 1967, the daily values given in the Bulletins differ somewhat from the values to be derived from the graphs which were also drawn up by AVA.
To estimate the maximum 24-hour flood the maximum figure from the Bulletin has been taken, to be on the safe side, des pite the fact that it may be somewhat suspect.
Applying the FUller’s method (bearing in mind the remarks made in para. 4.1.1) the straight line shown in Fig. 39 ensues. This represents the equation:
Q
max 
= 400 + 200 log T
&
4  2.2
From this it is possible to derive:
Q max 10               =       600 cu.m/sec
QmaxlOO            =       800 cu. m/sec
l     000 cu. m/sec
Qmax 1. 000 =  -
The 1,000-year discharge (1. 000 cu.m/sec) is 1.9 times the maximum discharge recorded during the 5 year observations (525 cu. m/sec).
Maximum Peak Discharge: QMAX (FUller’s Method)
The peak discharges of the annual floods (greatest discharge °  year or maximum of all 365 daily discharge values observed ln  a year) from 1964 to 1968 for the Kessem at the Awara
e lka Gauging Station are given a little farther ahead.
x amination of the data collected shows that the major floods n °rmally occur in August. They are short and generally last n ° longer than a day. but they reach considerable peak values ^hich do not differ greatly the one from the other. It should
e  noted that there are often discrepancies - sometimes con- 3l(lerable - between the daily flow values as shown in the
f- 30 -
Bulletins and those which may be derived from the AVA or The ones deemed most credible have been selected. Where B doubts have arisen, the higher values have been adopted Thefi are as follows:
Feature* of Maximum Peak Flood
Year
Month
Day
Diacharge
(Qmax    *  /"* )
cu    m      c
SUfe height
(h In m)
J 964
1966
1967
I960
August
Auguit
August
August
7
17
22
3
508 (a)
(•09Kb)
72® (b)
720 (»)
J. 12
«.2J)
(«. 00)
4. 00
Source:       (a) AVA Graph*.
(b) AVA Bulletin.
Beaming in mind the remarks made in para 4. 1. 1, Fig. 39 was constructed. The equation of the ’’FUller's line” is:
Qmax = 700 + 250 lo8 T
This gives the following maximum peak discharge values: QMAX IO =                  950       cu.m/sec
Q MAX 100 x h 200 cu’ra/flec
°MAX 1,000   1.450 cu.m/sec
x
The values of the 10-year. 100-year and 1, 000 year floods a1^c thus 1.2, 1.5 and 1.8 times the maximum event recorded in four year observations (809 cu.m/sec).
4. 2. 3 Flood from Creager's Equation Applying Creager’s equation:
q MAX = 46‘ C' A
r a(°- 894A-°- °48) - ] v
where:TIME (IN YEARS)
FIG. 39
PROBABLE MAXIMUM FLOODS FOR THE KESSEM RIVER AT AWARA MELKA (FULLER'S METHOD)- 31 -
^MAX
A
C
= flood discharge in cusecs/sq. mile
= catchment area in sq. miles
= Creager’s coefficient
The Kessem River at Awara Melka (3, 135 sq. km) has the
following value (with C = L 0):
Umax = i. isa cu. m/sec.
4.2.4 Total Maximum Observed Runoff Volume
The     main     runoffs     on     consecutive     days     over     the     period     consider ed are:
2
Tea r
Mc-m*
Flow
6
(1 a  CTL. ml
1964
19*5
w*t
tf*7
Hti
Augujl
Augu.it
Augvflt
Augmt
71h to J 4 th [B d*T»l
lit to 3rd. 11 d-ayil
Uth to ZOlh f? day*]
111* to 19th Pdiy<j
Jrd Lo 7th 0
iii.e
JI. 2
I6L 4
4fc I
17k 3
wil1 ke seen that the maximum flows over one or more con
secutive days for the Kessem at Awara Melka during the flood 
Gventfl examined are greater than those encountered in the same
yearB On the Awash at Awash Station (para. 4.1.3).
f ^°ods on the kebena at the ava station
24-Hour Flood:                          (Fllller'e Method)
j    8      Xn      the      preceding    cates,    the    maximum    annual    valueB    of    the ail V discharges set out in the AVA Bulletins have been examinedThe     daily     maxima     do     not     always     coincide,     in     time,     with     the values of the maximum peak discharge, as stated earlier.
Year
Month
Dav
Flow
(cu. m)
i Equal to Diachargt
a
(cu. m/aac)
1962
1965
ISM
1965
1964
196T
1966
Auguet
Augual
April
August
August
August
Aufuat
16
25
24
19
?
9-10
1
6. )65. J07
10.401,265
J J, 947.428
120. 4
161.4
4.584.489                                      5X J
8.640, 000
100. 0
8. 208. 000                                      95. 0
16. 070. 040
186. 0
Applying Fllller's method (but with the reservations already noted in para. 4.1.1) the line shown in Fig. 40 was drawn in. The equation of this line is:
Qmax                     = 11 2 + 11 5 log T
which indicates the following values:
Qmax 10             - 227 cu.m/sec
Qmax      100      =      342      cu.m/sec
Qmax 1,000 = 457 cu. m/sec
Maximum Peak Discharge: (Fllller's Method)
The following figures are for the peak discharges of the floods (greatest discharge of year or maximum of all 365 a r
^ d 
e
discharge values observed in a year) from 1962 to 1968 *eC at the AVA Gauging Station on the Kebena (basin area = 1« anT.TIME (IN YEARS)
FIG 40
PROBABLE MAXIMUM FLOOOS FOR THE KEBENA RIVER AT A.VA GAUGING STATION (FULLER'S METHOO )
□ .DISCHARGE |cum/wcl
^24996
ftAtcoiiitn!- 33 -
’ — ' ----------------------------------- ----------
f»ahar*« *< Madrwn P*ali
THr
Month
Dey
CM •chart*
‘°V(AXin
Stage
(h In *•)
nu
IS6J
ISM
IS**
ISO
IS* 7
19611
Auguat
July
Aaguat
No vw mb* r
Aufuil
Awpil
Auguat
i
)0
JI
7
7
»
J
its
>70
1JS
JJO
179
HI
6S9
a. r*
J. 10
1.99
X. 90
>. 10
X.6O
The stages reached by the peaks during the 1962. 1963. 1964. 1965 and 1966 floods indicated above are shown in Figs. 41 to 45.
The discharges have been deduced from the H. Q. scale in the FAO Report.
Following FUller’s method (accepting the reservations made in para. 4. I. 1) the 10-year, 100-year and I. 000 year events have been calculated, by tracing in the straight line having the equa« tion:
q max 3 361 + 334 log T
in Fig. 40.
From the equation it is possible to derive the following peak flood values;
Q MAX 10              =      695 cn.m/sec
Q MAX    100    s      L    029    cu.    m/sec
Q MAX I, 000 =              363 cu. m/sec
he values for 10-year, 100-year and 1,000-ycar frequency °ods are respectively 1.0, L. 5 and 2. 0 times the maximum
v *lue recorded during the seven year observations (695 cu -m/.ec).- 34
j j ylood from Creager's Equation
Applying C
reager's
Equation:
(0. 894A* -     j -
0   048
*IMAX
= 46. C. A.
where
q MAX
A
=• flood discharge in cusecs/square mile
= catchment area in square miles
C
= Creager's coefficient
2
then    the    Kebcna    River    at    the    AVA    Station    (area    1,    245    sq.km) has the following values:
QMAX   *782 cu.m/sec; for C = 10 
QMAX 2 1 • 564 cu.m/sec; for C = 20
4.3.4 Total Maximum Observed Runoff Volume
As in  previous cases,  the main  runoff volumes in  one or consecutive days recorded  during  the 1962-1968  observa
period, are given below:
Taar
Moclh
D-y
IH.1
IH)
IM4
IH5
IM6
IMT
IHl
A «at
M
air
April
AufBIl
Aigvat
Aog.ii
Aepti
|5th to 19th (5 daya)
)0<h to Slat (I daya)
ZJrdtoltth (« day•)
IJth to 10th (S daya)
7th to llth (5 daya)
5th to I0U (5 daya)
Jrd to 4lh (1 daya)
riow
(10 c“-
10. •
16 4
40.5
• a 1
JO. 1
4J. 1
IS. 1
nff *°r
During the 1968 event there occurred the
2 consecutive days (28. 1 million cu. m).
i*      RIVER      AT      A.V      A      GAUGING      « FLOOD OF AUGUST 2nd 1962
t-H-t
FT
— ♦---- r
1
o’•J
T
---
~M
PEAK..' 75 m
— <
t------ —\—
—t— .
v
2nd
I DAYS 1
AUGUST
REPRODUCTION OF THE ORIGINAL
PROM AVA
FIG ATKEBENA RIVER AT A.V.A. GAUGING STATION
FLOOD OF JULY 30,h 1963
JULY
REPRODUCTION OF THE ORIGINAL
FROM A.VA.
FIG. 42FROM A.V.A.NOVEMBER
REPRODUCTION OF THE ORIGINAL
FROM A.V.A.AUGUST
REPRODUCTION OF THE ORIGINAL
FROM A.V.A.
FIG. 45During the May 18th flood the diagrams indicate that reached a maximum stage of 2. 45 m, which - accord ° Wat*r scale H - Q of the FAO Report - corresponds to a
of 158 cu. m/sec. 
f° SC  'lr8e
The     average     discharge     of     the     flood out for the event in question: this
wave      has      also      been was 45. 7 cu. m/sec.
forked
Thus,     it     has     been     possible     to     calculate     the     ratio     between     the maximum peak discharge and the average discharge:
Qmax                 158
K=
max
’ 45. 7            ’ 3- 5
The value is somewhat higher than that found in other catch ments. However, the basin in question is smaller (1, 108 sq.km) and it has a fan-like form which helps increase the value of the peak discharge.
The event of September 16, 1964 is not of great importance because it was of too-short duration (about 2 hours).
As there is no other information available, the peakdischa g for various frequencies have been evaluated from the a
floods multiplied by the fore
Q MAX 10 
=   35
Q MAX 100 
=35
-
Q MAX 1.000 = 3- 5
It should be noted that the values are purely indieat
view    of    the    small    amount    of    information    on    which based.
E lood from Creager's Equation
According to Creager’s Equation:
where
***TIME (IN YEARS)
FIG. 46
probable maximum FLOODS FOR THE ARBA RIVER AT ARBA ( FULLER'S METHOD )
27002REPRODUCTION OF THE ORIGINAL
FROM A.V.A.
FIG. 47SEPTEMBER
REPRODUCTION OF THE ORIGINAL
FIG. 48- 37 -
A
C
=      flood      discharge      in      cusecs/square      mile = catchment area in square miles
- Creager’s coefficient
□MAX     for the Arba River at Arba (1, 108 sq.km) is:
757 cu. m/sec with C = 10
Total Maximum Observed Runoff Volume
As in  the case of the other rivers,  the maximum runoff covering one or more days has been  calculated  from measurements made
during observed events:
Year
Moath
Day
Voluma
(co. m)
ms
1964
1965
* 4-iy
August
July
14th                   (1 day) 25  th  lo  27th  (]  dayt)
IltM lo neb () day*)
7J4.430
4. W. 000
1. Ml. 622
It will be noted that in 1965 the day when the maximum daily Hood and the period when the maximum observed runoff volume occurred are in different months.
FLOODS on the awash in the study area
lo e
Sadi and Melka Warar Irrigation Districts cover a ^ road belt of terrain along the right bank of the Awash. 
e     Awash in this zone meanders first to the north (where it rc
at  eiVe° the KeBsem and the Kebena), then due east - almost angles - then northwest and finally- northeast.- 38 -
The two tributaries - the Kessem and the Kebena - join (h
Awash some 3 km apart, thus creating what might b  * 
e
a hydraulic '■knot". 
Because of the considerable flood flows of the two tributarieg (especially the Kessem), particularly close attention must paid to the hydrologic study here.
Two weirs for diverting irrigation waters are projected near the ’’knot”:
'”"d
the    first    (Melka    Sadi)    a    little    upstream    of    the    mouth    of the Kessem
the    second    (Melka    Warar)    a    little    below    where    the    Kebena joins the Awash.
4.5.2 Floods on the Awash at Melka Sadi
4 . 5. 2. 1 Flood Calculations by GherardeJHjind
Melka Sadi lies a few dozen kilometers downstream^^^^^
Awash Gauging Station and upstream of where the
gta.
and Kebena join the Awash. The catchment a^OV
^ . above
tion measures 20, 750 sq. km. though if the area y^ ^qq the Koka Dam is excluded this figure comes dow
sq. km.
r
The Arba is the only water course which joins tween Awash Station and Melka Sadi. The area .
• • a the Awash be' 
^ ba
r
Qn
 is
catchment is 1, 108 sq. km and the maxim urn e around 2, 430 m. Average annual rainfall val over 700 mm (at Arba) to a maximum of aroun 
a few small areas around the 2, 430-m level.
frO m a            * * ^qq m1*1 1
. \ToileV an » arV
nd i°d<5e
As a whole, flows are scarce in the Ar a
r
emain
S
the bed of the river at the Arba Gauging for many months of the year (January* Feb November and December).There are no data on which to base a events at the Melka Sadi section and >heref
>
o “'O<>d
r
evalnate the maximum Hood, it is necessary to use the pro-
cessed data for the Awash Gauging Station. There are vari
ous formulae for calculating flood discharges at a given sec’
lion, deriving them from another section in the same basin 
or a similar basin. The best are probably those framed by 
Gherardelli and Coutagne. According to Gherardelli, the
flood discharges Q, and Q? at Sections 1 and 2 in two similar
basins with respective catchments having areas S, and c
related by the following expression fl):                                                                   2 3rC -0,33 
Qi
. S' (1)
Q2
S 0.33
As   the   basin   area   Sj   at   Melka   Sadi   is   9»   500   sq.   km   and   that   at Awash Station (S2) is 7» 300 sq. km, then:
0. 33
Q  =
1
9, 500
0. 33 7, 300
1.09Q2
1. 09 hence with:
Qj = flood discharge at Melka Sadi
* flood discharge at Awash Station.
(0 D      erived from Gherardelli's formula:
h
q   ’ iioo(-4o>" "'
q          unit discharge in cu.m/sec
q ioo=  coefficient which represents the flood runoff
(cu. m/sec per sq. km) for a basin of 100 sq. km n        =    exponent fixed by Marchetti = 2/3 
S
area of catchment basin in 9q. km1
- 40 -
From what was said earlier the maximum 24-h
rn
year frequency at Melka Sadi is thus:
And the maximum peak discharge at Melka Sadi
°MAX 1, 000 ~ 1 ’ 09 x 1 • 1 75 = -L-280 cu. m/sec_ Si mi la r ly, in the case of 100-year floods
Qmax 100         = 1 • °9 x 515 = 561 cu.m/sec Q|4AX 100   1.09 x 900 = 981 cu. m/sec
=
and for 1 0-year floods
Qma* 10         ~         09 x 361 ~ 393 cu? rn/sec
Q MAX 10 = 1 • 09 x 625 = 681 cu.m/sec_
Coutagne, proposes the following expressions (after Myer) relating flood discharges at a given section and the corresponding catch ment:
Q = A S  where:
n
Q = flood discharge in cu. rn/sec at a given sect
S = the catchment basin in sq. km
n - coefficient varying from 0. 50 to 0. 75
A x coefficient which varies regionally accor.Qn> morphological features of the area in qu
Applying this expression to the Awash S
sections   and   fixing   n   at   0.   75   (see   Mauri sance     des     crues     en     diverses     parties     du en Afrique Noire), the maximum 24-hot
discharge both with 1,000-year frequency a rnultipb'ing ' obtained from the figures for Awash Stat>orl • 
latter by 1.22 (I).
• • g the £ 
tation and Melka Sadi
ce Parde: "Sur la puis- monde" - Crues Records
ir flood and maximuni pe& ftadi can be
__
9, 500 °- 7$ 7, 300        75
1.22- 41 -
Hence, at Melka Sadi:
r-t .  = l.22x 
u
max 1,000 
O , . 
U
MAX 1,000
669 = 8l6cu.m/sec --------------- -------
~ 1.22 x 1, 175 = 1,433 cu. m./gec,
While, for the lOO-year frequency:
Qmajc 100
Q MAX 100 And for 10-year frequency:
^majt 10 
Q MAX 10 
1.22 x 515
1.22 x 900
628 cu. m/sec 1, 098 cu, m/sec
~ 1.22 x 361
= 1.22 x 625
440 cu, m/sec
762 cu.m /sec
For     the     1,     000-year     maximum     peak     discharge,     the     coefficient     A in the Coutagne-Parde formula is:
Q                    1.433 
=sn
9. 500 '
. _ 3/4      * ‘■4’
It   should   be   noted   that   for   the   Milo   at   Kankan   (Africa)   (Area   = 9. 900 sq. km) the maximum peak discharge observed is (1):
^MAX    ’    1,    300    cu.    m/sec c °rresponding to an A value of 1.31.
Creager's Equation: ^ax = 46. C. A. <°‘ 894A’°‘ °48) "1
where:
(I)
ee Maurice Parde - "Sur la puissance des crues en  diver- 8es parties du  monde11,  1961.  Tableau  18  - Crues-Records en  Afriq  N i
ue     o re (page 174).- 42 -
9 max
= flood discharge in cusecs/square mile
A
— catchment area in square mileg
C
= Creager’s coefficient
Q MAX for the Awash River at Melka Sadi
1,843 cu.m/sec with C = 10 4 5.3 Floods on the Awash at Melka Warar
(9, 500 sq. -b
4,5. 3. 1      Flp^d ^Calculation^by_Ghera£de21i.’_s-and ^outagne_^Formulae
Melka     Warar     lies     a     little     downstream     from     where    the     Awash receives the Kessem and Kebena on its left bank.
At the Awara Melka Station, the Kessem has a catchment of 3, 135 sq.km. Average annual rainfall in this basin varies
from 500 to 1, 900 mm. Maximum observed runoff occurred between August 3 and 7, 1968 with 175. 3 million cubic meters.
The area of the Kebena catchment at the measuring station
1,245 sq.km. Average annual rainfall varies fro mm. The range is broadly the same as that of the Ke
sc ni.
as the Kebena basin is smaller and more compact t
9 ia
j ped 
gradient is greater; moreover, the Kebena basin is gicierabie
which favors the occurrence of frequent events of c ^ uri)-
o
intensity but short duration (generally not exceed g
The maximum observed runoff occurred between 
10th, 1967 with 43. 1 million cubic meters, 
the     entity     of     the     maximum     flood,     using     Gherar
August
5th
as^efl5^
eXpre5Sl
once
again, then:
Qt
S,  °* 33
wh er e:
=
Q               S n     0'33 O
Q1
Q
flood      discharge      at      Melka      Warar fiood discharge at Awash Station- 43 -
Si
S
-    area of Melka Warar basin (sq. km)
- area of basin at Awash Station (sq. km)
Qj                s 1 27 and hence:
-0"
Maximum 1. 000-year.frequency floods.
Qmax 1. 000              = E27x QMAX 1,000            =    1- 27 x 1,
100-year floods
669 = 850 cu. m/sec
175 = 1.492 cu. m/sec
QmaxlOO
= U7
x
515 =
654 cu. m/sec
□ MAX 100 
=
1- 27 x
900 =
1, 143 cu. m/sec
1 0-year floods
Q max 10 
= 1.27 x
361 -
458 cu. m/sec
Q MAX 10 
= 1.27 x
625 =
794 cu. m/sec
U
Applying Coutagne’s formula:
Q
« 0. 75
1       _ S1
Q            s °- 75
Ql = flood discharge at Melka Wara-
where:
Q     =     flood     discharge     at     Awash     Station \ = catchment basin at Melka Warar (eq. k">)
S      = catchment ba.in at Awash Station (sq. tan) Pl = 1.71
Q
Nence
w ith i
the maximum 24-hour flood and maximum peak discharges -AQO-year frequency are:
1,000          = l-71 x 669 = !■
144 cu  m gec
-/
Q Max 1 nnn = 1.71 x 1,175 = 2, 009 cu. m/secSimilarly for the 100-year floods:
^max
= 1. 71 X 515
=
 881
cu. m/sec
q max
= 1. 71 x 900
=
 1.539
CU. m/sec
and for the
! 0-year floods:
Qmax
= 1. 71 x 361
=
617
cu. m/sec
q max
= I. 71 x 625
=
1. 069
cu. m/sec
Examining    the    data    found, 
the Melka Warar section <
, it is seen that the flood values at
on the Awash are slightly higher than 
those at Awara Melka on the Kessem, and this although the Melka Warar section is below the confluence of the Kessem
and the Awash (e. g. :
Kessem at Awara Melka:
Q max 100 = 800 cu. m/sec; Qmax 1, 000 ~ Awash fit Melka Warar (Coutagne):
1. 000 cu. m/sec
Q m.tx 100 ' 881 cu. m/sec; Q
, 
=    1, 144 cu. m/sec).
This is due to the fact that - as has been repeated several
t.mes - no direct observations are available for the section Jnder study, and hence the flood values of the Awash at Melka Warar have been calculated by deduction from those obtained hy analyzing the series of data available at Awash Station (a short series for processing of the sort).
However,     the     Melka tion: at the hydrauli
Warar section is situated in a special P°^ c knot caused by the union of three riv
of the
d
<nd  ^at even tJle data collected indicate the siz e5 ° f                Ke..™ (the maximum flood
Warar.’u ,*“t?
Awe.M the Kes«'>>' are greater than those observed >"
s            eClded t0 canulate the flood discharges a those of the k crardelli expression and deducing them
essem at Awara Melka - viz. as though t e
t  Mel**... fro^
M^3- 45 -~
VVara  section were in the Kessem basin. The values shown in 
r
Table 58 were found in this wav (Table 58: /"’The Kessem at Melka Warar_7)-
The latter values are obviously considerably higher than those found earlier, but they are significant for the purpose of de signing, the hydraulic works planned for the area.
4 5.3.2 FLo^d Xrpj^Ci^a^er_'^_E£^atipn
Using Creager’s equation, with the symbols and coefficients as before, the flood on the Awash at Melka Warar (area = 14, 900 sq. km):
q max
2, 160 cu. m/scc                     with C = 10
The maximum 24-hour floods and the maximum peak discharges
with 10-year, 100-year and 1, 000-year frequencies are given 
in Table 58. The Specific Runoff Values are also included for
the 1, 000-year frequencies.
EVALUATION of the roughness of the awash in the study area
Th
e  coefficient of roughness (K) which it is desired to deter
mine i  that
s            o{ the Gauckler.Manning-Strickler formula (I)
lid for uniform flow in canals:
U = Km °‘67i °'50
Thls       formula    is    known    in    Europe    generally    as    the    Strickler
f °rmul , 
a
and     in     English-speaking     countries     as     the     Manning 
£ °rmula.- 46 -
where:
U = average speed (in m/sec)
m = hydraulic radius
i = hydraulic gradient
Using  the discharge measurements taken  and  knowing  the cor responding  hydrometric depth,  the values of m were obtained 
This    enabled    the    values    of    the    roughness    coefficient    K    also    t
o
be calculated. The following results were thus obtained: For the Awash at Melka Sadi (Fig. 49)
For H = 0. 70 m and Q - 21.06 cu. m/sec
S
=
60. 75 sq. m
m
=
hydraulic radius = 2. 02
i
=
0.001
V”      =   0. 35 m/sec
K =7
For H = 1.60m and Q = 64. 15 cu. m/sec
S         =   91. 1 7  sci.m
m        =   2. 76
i          =   0.001
V m      =   0. 70 m/sec
K =17
The coefficient of roughness K varies between 7 an^ These truly low values are due to the moderate  P measured in the two discharge measurements f°u
1 *7
S
during low water.FIG. 49
AWASH RIVER
MELKA-SADI GAUGING STATION (CROSS-SECTION)
HWL
CROSS-SECTION
scales :
Horizontal
Vertical
DISCHARGE MEASUREMENTS
DAT   E
H
Q
22 10 ■ 1968
26    12    1966
14      1     1968
25     5     1968
2      3     1968
21      8     1968
0 70
0 79
1 04
1 05
1 09
1 46
20      8     1968
1 60
21 06
32 30
33 76
39 00
36 46
61 20
64 15
PLAN
[ I T A LCONSU- 47 -
For the Awash at Melka Warar (Fi  50)
g
For H = (L 47 m and Q = 27. 7 cu.m /.er
s       = 46 sq. m
m
= hydraulic radius = 1.67
i
= 0.0005
Vm
= 0. 60 m/sec
K
= 19. 1
For
H = 5. 23 m
and 
Q = 299. 2 cu. m/sec
s
= 232. 4 sq. m
m
= 4. 04
i
= 0.0005
vmm
= 0. 99 m/sec
K
= 17. 4
The    coefficient of roughness (K) therefore varies be- tween 1 7. 4 and 19. 1.
t*on, and on t
SEDIMENT measurements and water analysis
Tables 59 and 60 show the values of solid load for the hydro- lo gic years 1965 and 1966-1967, on the Awash at Awash Sta-
j  K
y* r 1966-1967, the observations on the Awash at Metehara
le     e8sem at Awara Melka. For the hydrologic
a
Bection are also given.
Table. 61. 62 and 63 .Ho« -.nd 
t^ents of solid load (in gr/Ut). o
a nd of the pH value.
. River at Awash
e-FIG. 50
AWASH RIVER
melka warar gauging station (cross-section)
DISCHARGE MEASUREMENTS
DATE
H
Q (cu.m/*»c
16 8 1968
9 9 1967
16 8 1968
158 1968
16 9 1967
24 7 1967
3 3 1968
24. 5 1968
24. 10 1968
13    1 1968
23 12 1966 3 6 1967
5.33
5 23
4 45
3 86
2 78
1 87
1 02
0.46
0 51
0 47
0.45
0 40
224 6
229 2
178 8
166 8
99. 3
90 9
48 4
42 1
29 5
27.7
26 0
26.5
AWASH rive*
^AyoiNG
PLAN
27006
ITALCOnjuLT- 49 .
5, water availability
The construction of the Koka dam and the coming into operation of the h droelectric plant - with the marked increase in the river Awash flows daring the dry season - provided the initiative for a whole
series of irrigation projets along the entire river valley; this
situation is still in continuous evolution. Regular concessions have been granted for part of these irrigation areas, whereas in others full and final regulation is still lacking. From a model concession con tract drawn up by the AVA, it emerges that one of the concessionary*s commitments is that of submitting the proposed cropping pattern and estimated monthly water requirements for approval by the Authority. Upto now, however, no precise data have been available either from the AVA or from the concessionaries regarding these water require ments or possible water rights resulting from the contracts or from other arrangements.
On the basis of the discharges of the Awash river during the hydro- logical year 1962-1963 and of likely cropping patterns, the 1965 FAO Report concluded that, in the first phase, i. e. before the construction of any further compensating reservoir or of the diversion of the Meki R*VCr» it would be possible to reclaim 63, 400 ha - 12, 000 of these be-
in the Upper Valley, 19, 500 in the Middle Valley and 31, 900 in the  Lower Valley.
The
r  ac*uai situation is somewhat different from the forecast, both as c ^ ards the si2e (number of ha) of the various holdings and as regards fro PPlng Patterns too. Therefore, the amount of water to be diverted
e
iRe Awash has also changed.
new water balance two stretches:
i   it has been deemed advisable to
Meiv rSt Stretch- which runs to a point downstream of the weir of Warar and embraces the Upper and Middle Valley;
er^hSeC°nd atretch runs to a point downstream of Tendaho and ace s the Lower Valley.dow stretns ch y   tream streicn
4  stream stretch is hydraulically separated from the
Tbv the Gewani swamps. Furthermore possible shortage, in . 
. be handled within the framework of the
resources of that section (1).
Upsl^m
^ater
Therefore, 
considered.
only the water balance of the Melka Warar section will be
The component parts of the balance are the following:
Water resources. Flows at the Melka Warar section hav obtained by adding the flows of the Awash at Awash Statio *** of the Kessem and Kebena rivers. 
n t0 those
Therefore     the     contributions     from     the     basin     between     Awash     Station and Melka Warar have not been taken into account.
Irrigation requirements. For the areas upstream of Awash Station, the figures forecast in the 3rd Five-year Plan have been assumed as follows:
Upper Valley Wonji
Nura Era - Tibila Middle Valley
13.500 ha
7, 000 ha
6.500 ha
12, 800 ha.
Metehara
Abadi r
Others
in actual fact Wonji has not been taken into considerate flow measurements were started at Awash Station, area was already in operation.
8, 000 ha 4,000 ha
800 ha
bec^uS^ irrigat
________ _____________ ______________ __________— (1) See: Melka Sadi-Amibara - Feasibility Study.
Italconsult, Rome.
Incepti»» - 51 -
0
network losses, net of the amount restored to the river through drains and/or groundwaters are equivalent to 20% of the require- ments. 
The results of the calculations are outlined in Table 65.
In order to calculate water consumption in the Melka Sadi-Amibara District, all the cropping patterns considered in the agronomic study (see Part II, Volume 5) have been examined, taking account of the decadal field irrigation requirements in each case (see Table 66). Then, the maximum requirements for each ten-day period of the year were chosen from among all the cropping patterns considered (see Table 67, column 2).
for the areas upstream of Awash Station th
per net hectare have been calculated on th. J *ater "quires pj,terns and climatic data. The reault, are ,p“
direr.mn requirement, were then calculat" "
. 20% of the commanded area i.
dykes, farm building., dwelling ,"^"* 
crpppin" '
“ TaW' 6« Th
canal., drain..
H
Table     67,     column     3,     indicates     the     gross     offtake     requirements     at     the diversion
*“----ri„i weir including the network losses as they were calculated in Part II, Volume 4.
These figures, when multiplied by the gross area  8
1    1V®
_ ation of
8
ln cu.m/sec    (Table    67,    column    5)    to    be    diverted    for    the    irr    g Melka Sadi-Amibara District. The total irrigation
'“•m/sec (column 7) and in cu. m/day (column 8) wer* y adding to these the values of the upstream areas (
column 6).
^AXhe<*          daily              fl°WS              Wer*          then              COmP7theTeh3semnaatUAwara          Melka
and of at Awash Station, plus those of t
It     8li        he       Kebena     for     the     period     from     November °uld be noted:
October 1968.
77" fl°WS at AWH8h Stati°n arC alrrd7 ?he
he  quantities abstracted upstream during P
ah
R        Urp erUd conBidered 
•g- irrigation of Wonji Estate);2) that the flows of the Kessem at Awara Melka and of the K
not include anv abstractions downstream of the gaugin'5 ebena d° which would only amount to a few hundred 1/sec;
3) that the regime of flows of the Kessem will be modified b construction of the reservoir. 
The following points emerge from the foregoing comparison ~
». aeficiene, .broo hou  -nth
8 8tations
y tlle
tsee Tabled
gt
January
Februar
2nd decade:
1963:
1 isolated daily deficiency 1 isolated daily deficiency
1%7:
1 isolated daily deficiency 3rd decade:
of  93.  946  cu.  m
of 47. 223 cu. m
Of 23. 445 CU.     m
1963:
1 isolated daily deficiency of 1 isolated daily deficiency of
386,784 «■” 247.392 c«.n>
1 isolated daily deficiency
of
65. 594 cu-1”- 53 -
Ht-decade:
L21Z:
4 daily deficiencies in 5 consecutive days with maximum daily deficiencies of 377, 997 cu.m and with a total maximum defi ciency for the 5 days of 404, 180 cu.m.
2nd decade^
1967:
3 daily deficiencies in 4 consecutive days with a maximum daily deficiency of 234, 144 cu.m and with a maximum total deficiency for that period of 451,669
1 daily deficiency of 165, 715 cu.m 1 daily deficiency of 209. 952 cu.m.
no deficiency
no  deficiency deficiency
° deficiencySeptember: no deficiency October:
1st decade: no deficiency 2nd decade:
1967:
1 isolated
daily deficiency           of         14, 813
cu.   rn
1 isolated
daily deficiency
of
98, 280
cu.
m
1 isolated
daily deficiency
of
7, 560
cu.
m
1 isolated
daily deficiency
of
764, 920
cu.
m
1968:
I isolated      daily deficiency           of        83, 808  cu. m 3rd decade:
1965:
1 isolated daily deficiency of 429, 408 cu. m 1966:
1 isolated daily deficiency of 2 38, 464 cu. m
1 isolated daily deficiency of 426, 816 cu. m November:
1st decade:
1965:
l daily deficiencies in 3 consecutive days, W1 daily deficiency of 794, 448 cu. m and a maximum for the period of I, 254, 269 cu. m.
* t'h a
deficie
urn- 55 -
1266L
1 isolated daily deficiency of 82, 944 cu m
I isolated daily deficiency of 1 95, 264 cu.m
1 isolated daily deficiency of 101, 261 cu.m
1 isolated daily deficiency of 193, 882 cu.m
2nd d ecadc; no deficiency
3rd decade:
1262:
6 daily deficiencies on 6 consecutive days with a maximum dai ly deficiency of 521, 453 cu.m and a maximum deficiency for the period of 1, 055, 118 cu.m
It is to be noted that although the monthly flow for November 1966 (65. 80 x 106 cu.m) was less than that of November 1962 (82. 48 x 10^ cu. m), in the latter year the flows were lower
in the last decade.
»P^
-Lit decad-e*
isolated daily deficiency of 75, 168 cu.301 e  thC fi8ures aet forth above, it will be sees
h 1 de“ciency for the years considered wool
that the maximum
li2 54,269
dc(iciency
^uld v’1 decade °f November, 1965). H°w
creates a reservoir
*ith 
a Ve
aVe        keen     less     since     the     Melka     Warar        part       0£     this     reservoir
16
 u
aed
^  of approximately 650,000 cu.^ *■ °Ver a 24-hour period - to con r
discharges with * the discharges o
the
their avera8e- Durin
vary over a considerable range
8 
the day
* because of the Koka power- 56-
station, as shown in Fig. 51. This range, is reduced with the
into operation of Awash 2 (see 2nd part of the diagram in Fi
can thus be estimated that a volume of some 200, 000 cu. m i^
for daily regulation. The remaining part of the reservoir create
the weir may therefore be emptied from time to time when tho * 
daily discharges are lower than the irrigation requirement
In the case of the maximum deficiency (November, 1965) it would hav been possible to draw of about 450, 000 cu. m and the actual deficie would thus have been reduced to approximately 800, 000 cu. m
Hence, by using the reservoir created by the weir even for carrying over volumes of water from one day to another (apart from regulation over a 24-hour period) it would have been possible to completely eli minate all deficiencies of less than 450, 000 cu. m. In other words it would have been possible to eliminate all the deficiencies encountered in February, March and December.
In brief, examination of the November 1962-October 1968 period shows that there should have been deficiencies of some importance on the
following days:
October 1967:                 isolated daily deficiency of 764,920 cu- m
11
ge
November 1965; 1962:
(1st decade): deficiency on one day of 794,448 cu. with total deficiencies over three days of 1,254,2
i
(3rd decade); deficiency on one day of
with a total deficiency over 6 consecutive days 1, 055, 118 cu. m
9 l 4 5 3 c u. ‘ QlYlpT 0 ~
It may therefore be said that these deficiencies would not hav mised the crops on the lands in the Study Area. However, i / ec
s
1967 (31st) the flow was only 1, 110, 240 cu. m, i. e. 12. 85 cu. Awash Station which would not have been sufficient to irriga aj]ovvi ^
n
stream areas (Nura Era, Nletehara, Abadir and others)
for losses due to evaporation or infiltration in the districts of Awash Station. Thus it is suggested that EELPA should following average daily discharges (net of losses due to evap
tre am
the
otFIG. 51
AWASH RIVER
CORRELATION BETWEEN ISTANTANEOUS DISCHARGES OF KOKA, WONGI AND AWASH STATION- 57 -
nitration and that represent the total requirements at the diversion ’ r as ^own in Table 67, column 7) to be controlled with a staff RauBe * be set up in a stable section of the Awash just upstream of the first :r rigation district:
January =
February -
I 5 cu. m/sec
21 cu. m/sec
.March
April
X                 26 cu. m/sec
=
May                      =
June
July
=
=
August =
September =
October
Member
Member
amounts whi K
18 cu. m/9ec
1 3 cu. m/sec
19 cu. m/sec
21 cu. m/scc
25 cu. m/sec
34 cu. m/sec
31 cu. m/sec
to cu. m/sec 14 cu. m/sec
^ !>ern ancj k C may already be being abstracted downstream of the sJl °uld  u. *
a         na measuring stations (not assessed in this evaluation)
Od «d to the foregoing value..
dr<?a» indicat*^* 8tatec^ *hat it is possible to reclaim and irrigate
'h
^ive-Year Plan, and the area of the
P tcd:
ra        rea
 A“    p
rovided the following assumptions are
’ Th* cm
Ij ~ ^Ppin
l ^a tio  Area
n
a nd the water requirements of the various
* 
8 rornain 
as previously indicated;
t 0 A ^Ust poa
t !(j *hakl0 jt 8<5a“ all the required legal and technical instruments Ot ^ th© Awu^^ anc^» if necessary, to limit discharges divert-
Alj . 
*  river and its tributaries;
8
c a rea
a
^4 ^Urij118^ divert their own irrigation allocations from the
netu/fA i°U* 
an d return the waters collected by their
vo  inc river;- 58 -
-    The Koka reservoir and the relative hydroelectric plants
managed following criteria analogous to those adopted in iqa** be the minimum daily discharges indicated above must Ko . 
With regard to the availability of water downstream of the Ar stretches have been considered:
-    from the Melka Warar weir to the northern border of the Area
-    from the northern extremity of the Area to Gewani Swamp
’ atKl
e rc spected.
*rea, t\vo 
Since    the    Gewani    Swamp    provides    a    hydraulic    break    in    the    continuity    of the river, there will hardly be any repercussions downstream of Gewani.
Of the two stretches, the effects of diverting waters from the Awash will be felt most in the first (which delimits the Area to the northwest). Nonetheless in this limited stretch, the amount of water necessary for the needs of man and beast alike (including fish) will be guaranteed. Indeed, it emerges from the investigations and the foregoing consider ations that if irrigation had been practised over the six-year period a- nalyzed, shortages of water would only have occurred on three days. This means that on those three days the Melka Warar weir would have diverted all the waters flowing in that section. However, even in 
unfavorable hypothesis, the water stored in the bed of the ^
r
VC ^W^r-e£ 
have been sufficient for the modest needs of man and beast for t period involved (a few hours).
Anyway, in such rare cases it would always be possible to 
discharge of 1-2 cu. m/sec to run dowm the river. Natura ?<
wO uld
ccrta n
j iy 
be at the expense of the irrigation area but the crops woU withstand the ensuing deficit for the short period involve
When the Area is reclaimed it would be
wells to ensure that the inhabitants have
available, since pollution tends to occur
periods.
Conditions in the other stretch of river arc m
will be possible to count on flows from Awash Cocai) and on the return to the river of excess irrig
advisable to sink a number of sufficient water of good qualit} rather easily during low-fl°u
. ^arkedlv better
ar ies (suc^
w aters.
h<r1
Tabla 1
MEAN MONTHLT RAINFALL (mm)
mb*
Elevation: 1.540 m a, >. 1.
N
F
M
A
M
J
J
A
S
0
D
Total
!•**
J 00
45.5 66.0 12.0
o.o 0.0 10
ii.a 27.5
0. 0
0.0
4.0
77. 0
12. 0
75.0
5J.0
1. 0
3. 0
0. 0
0. 0
0. 0
0.0
95. 0
0. 0
51.0
Lit
61. 0
37. 0
57. 0
93. 0
37. 0
56. 0
50. 0
50. 0
61. o
62. 0
«5.o
0. o
83. *>
48. 0
33. 0
102. 0
62.0
77. 0
16 0
27. 0
17. 6
111.0
57. 0
31.0
2nd
44. 0
35. 0
45. 0
69. 0
27 0
55,0
45. 0
27.0
55.0
39.0
42. 0
62. 0
36.9
45.5
365.0
251.5
91.6
33.5
0.0
0.0
963.0
iHJ
10*
10*
lU»
?u
.9b>
IM
HT
Ml
19. 0
41.0
20. 0
51.0
25. 0
140. 0
104. 0
52. 0
63. 0
IB. 0
69. 0
Irsl
40. 0
35. 0
37. 0
46. 0
25. 0
50. 0
40. 0
26. 0
47. 0
27. 0
26 0
26. 0
64. 0
19. 0
10. 0
13.0
1 34. 0
1 04. 0
I. 0
31.0
61. 0
4. 0
max. 24
97, 0
66. 0
46. 0
104. 0
33. 0
54. 0
103. 0
30. 0
85. 0
78. 0
148.0
- hour ev
355. 0
170. 0
106. 0
116.0
192. 0
278. 0
167.0
120. 0
329. 0
162. 0
158. 0
rnt (in m
267. 0
140. 0
189. 0
371.0
91.0
J47.0
178.0
207. 0
293.0
156. 0
20.7
91. 0
179.0
180 0
86.0
87.0
140.0
61.0
120. 0
84.0
64. 0
ii. a
14.0
0.0
22 0
52.0
0.0
22.0
42.0
21.0
54. 0
4.0
50
1. 0
4. 0
42.0
6.0
9. 0
2. 0
14.0
00
112. 0
2. 0
0. 0
32.0
1. 0
o.o
60
40.0
2.5
0.0
0.0
0. 0
i. 0
1,009. 7
707 0
961.0
581 0
1.106 0
860. 5
572. 1
1.148 0
•
692. 0
UM
iiM
me
Ml
M2
H)
IH5
mb
’M?
’Kt
^’41
’Ha...
50 ^r.od
‘ ***nCoU:
1958-lge    8 H. V.A,MEAN MONTHLY RAINFALL (mm)
Station: KOKA
Year
1962
1963
1964
1965
1966
1967
1968
J
M
A
M
J
0. 0 6. I
13. 7
0. 0 0. 0
0. 0
0. 0
0. 0 14 0
1 at (9. 5)
122.4
85. 0
5. 5
41.4
42. 8
144. 8
32. 0 2nd
60. 3
68. 3
84. 0 100. 2
9. 1 134. 9
49. 0 3rd 51. 5
66. 0
6. 5
127. 4
0. 0
53. 6
0. 0
max.24
17. 3
72. 8
13. 5
263. 5
350. 5
155. 5 272. 1
115.4
110. 0
95.2
35.9
76. 0
114.5           90. 0
30. 0
0 7.1
0. 0
31.0
47.1
3.4
48.5
0.0
0.5 14.3
0.0 o.o
0.0 48.0
U.4
JOC
M to
0.01 0.0
hour e4cnt (in nj
m)
1962
1963
1964
1965
1966
1967
1968
33. 6
30. 5
21.4
(32.5)
(24. 0)
(16. 0)
(80. 0)
(48. 0)
(30. 0)
36. 0
26. 0
19. 0
Source   : AV ATabla J
MEAN MONTHLY RAINFALL (mm)
Ovation: 955 m a. 8. L
A S O N D Total
64. 1
23.9
08
5.2
0. 0
12  6
17. 0
I 3* 0
121.4
25 S
0. 0
35 5
17 4
JO. 6
25. 4
215. 6
142. a
52. 4
13 0
0.0
13.6
I0
3. 2
60 0
101  0
40 0
36 0
16 0
00
406 4
!!.   0
44. 0
128. 0
169 0
9 3. 0
JO 0
00
657. 0
51. 0
52 0
119 0
2 30. 0
51 0
44 0
00
7«J. 0
55
41. 0
80. 0
43 5
10. 5
4.0
110.0
31.0
14. 0
Jrd 11.  5
2 3. 0
max. 24]     hour cveht (in mm
Ibi
lUJ
lot 44. 3
25 0
2nd
14. 5
24. 0
W. 4
24 0
26. 0
11H
58 0
17. 0
34. 0
iw
48. 0
40. 0
ia. o
mi
IM
40. 0
40. 0
40. 0
25. 5
2 3. 0
14. 0
JMEAN MONTHLY RAINFALL (mm)
Station:              SHE NO
lit
Year
J
F
M
A
M
1962
1963
1 964
1965
1966
1 967
1968
4. 3
13. 8
7. 9
8. 7
0. 0
0. 0
10.2 16. 3
0. 0 63. 6
0. 0 51.8
12. 5
46. 0
73.7
14. 0
57.3
14. 6
87. 1
84. 0
56. 0
35. 8
80. 2 154. 6
54. 8
44.2
0. 0
0. 0
39.2
68. 0
AVA.Table 5
MEAN MONTHLY RAINFALL (mm)
Election: 105 m a. *. I.
F
II00
2122..55
l»i 17 0
0)
67. 2MEAN MONTHLY RAINFALL (mm)
Station: AWASH STATION
Year
J
F
M
A
M
J
J
19 37
19 38
19 39
1940
1962
1963
1964
1965
1966
1967
1968
-
28. 5
12. 0
0. 0
-
0. 0
0. 0
72. 2
12. 7
28. 5
174. 6
0. 0
55. 8
-
10. 9
32. 5
-
-
0. 0
13. 9
0. 0
0. 0
0. 0
20. 0
148 5 241. 0
5
183.  9
202.  1
I 30.  4
1937
1938
19 39
1940
1962
1963
1964
1965
1966
1967
1968
62.
-
0. 4
0. 0
0. 0
160. 4
0. 0
233. 4
1st
82. 2
26. 5
61. 0
45. 0
(37. 4)
62. 0
50. 0
66. 5
49. 3
71. 5
39. 5
-
22. 7
0. 0
67. 8
29. 7
64. 0
25. 6
2nd
r
26. 0
19. 5
34. 0
39. 5
(37. 2)
51. 8
36. 0
50 0
48. 6
48. 5
38. 0
-
169. 2
33. 1
159. 0
70 6
66. 1
141. 9
3rd
15. 0
19. 0
23. 5
-
(36 2)
33. 4
33. 4
42. 0
47. 0
40. 7
33. 5
131. 8
61. 1
0. 0
19. 6
74. 9
7. 3
max. 24
27. 4
17. 0
-
19. 7
6. 7
30. 7
21. 5
39. 1
65. 2
80. 5
hour eve
57 5
99 5
117 8
-
199. 1
139 2
127. 1
41. 5
146. 8
72. 7
110. 9 it (in mm
•
1940 period - Fantoli; 1962-1968 AVA.Table 7'
aERHAN
Elevation; 2. 802 m a. a. I.
Total
265. 4       263. 3
369. 7       366. 4
369. 8       243. 6
267. 0       280. 8
I. 083. 7
902.6
716. 0
196. 2       288. 0
913. I
666. 5       JIB. 5
1,434. 8
335. 4       212. 4
I, 174. IMEAN MONTHLY
Station:          MELKA WARAR
Mean Annual Rainfall over the Period (1966 not included): 576. 2 mm
RAINFALL (mm)
Year
1965
1967
1968
Average
J
9. 5
0
0
3. 2
F
0
0
96. 3
32. I
M
33. 5
89. 5
3. 1
42. I
A
77. 6
8. 5
92. 2
59. 4
J
7JS
J
0
72. 0
2. 2
24. 7
0
24. 7
55. 8
26. 8
41. 0
13L 0
130. 7
100. 9
A
91. 5
218. 5
145. 6
151. 9
S
58. 0
17. 5
46.4
40. 6
o
12.5
22. 2
12.0
15.6
94 4
41.2
7G 0
0
»4
1965
1966
1967
1968
3
0
0
0
0
12
0
11
2
3
7
2
13
3
3
11
0
3
6
3
R a i n y D ■ Monthly Total!
0
7
5
6
12
13
22
17
13
8
11
5
11
Source: AVA.TableB (Coot. )l
DAILY RAINFALL (mm)
Etcvflion: 750 m a. a. 1.
M
A
M
J
J
A
5
0
N
D
Total
I. o
5. 6
10. 5
8. 0
0. 5
0. 5
9.0
0. 5
10.0
4.5
3.5
0.5
5.5
1.5
I. 0
31.5
6.5
1.5
21.0
4.5
2. 5
13. 5
1.5
11. 5
3. 0
4.5
5.0
30. 0
2. 5
8.0
1.5
8.5
10.0
1.0
2.5
1.5
13.5
19.5
9.5
6.5
2.0
14. 5
5. 0
13.0
20. 5
0. 5
3. 5
16.0
0. 5
1. 5
5. 5
1. 5
1.5
0. 5
2. 0
t.5
J. 0
3.5
TTi 2
77.6
13
0
0
0
0
41
11
91.5
16
58
8
12.5
3
74
5
0
0
397. 6
61DAILY RAINFALL (mm)
Station:      MELKA      WARAR Year: 1966
Soured AVA •
♦.xTitle B {Con
DAILY RAINFALL (mm)DAILY RAINFALL (mm)
Station: MELKA WARAR Year: 1968
Diy
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
J
F
6. 0
M
1. 6
A
M
J
4. 5
4. 5
J
0. 5
4. 5
4. 6
A
12. 2 49. 0
2. 8
s
o
N
D
2. 8
1. 0
4. 4
8. 7
10. 0
1. 5
2. 6
2. 5
15. 5
9. 5
0. 7
4. 5
6.0
35.0
4. 4 18. 2
1. 4
0. 7
3.0
6. 2
3. 0
31. 0
8. 4
1. 2
5. 0
1. 4
30.0
12.0
4. 7
0. 5
3. 6
2.0
4. 6
5. 3
2. 0
12.0
6.8
22.2
6. 6
lz. 2
4. 0
2. 8
30. 5
1. 4
4. 0
I. 0
20. 9
9. 8
9. 5
2.0
26. 0
2. 0
25. 0
1. 6
3. 0
9. 0
5. 5
2. 0
1. 5
Hl [
U
1
0.1
34. 4
10.0
3. 5
4. 0
8. 8
TeT---------
otaXrrm) requen-
ics
0
0
96. 3
11
3. 1
2
92. 2
11
2. 2
3
TO
6
1 30. V
13
■,.EA
1 45. a
n______
S'
**
J___
Source: AVA| (Cont. | 5
DECADAL RAINFALL
SfelervitUn P »od: 1965-1968
rr
M
J
J
A
S
0
N
1
D
Total
0
D
0
0
0
0
0
0
0
0
0
0
0
0
16.5 16. 5
65
30. 0
0. 5
37. 0
4.5
19. 0
17. 5
41, 0
-O
49.5
33.5
8.5
91.5
37.0
19.5
1.5
58. 0
12.5
0
0
12.5
74.0
0
0
74. 0
36. 0
54.5
51. 0
141.5
10. 0
60. 0
17.0
87.0
0
0
0
0
0
0
0
0
0
0
0
0
62. 0 10. 0
0 72. 0
10. 7
0
14. 0
24. 7
46. 0
62. 0
86. 0
30.5
17.5
0
20.2
2. 0
23. 0       102.0                             0
131. 0       219.5
22.2
0
82. 1
12.8
94.9
0
0
0
0
0 1.2 1. 0
2. 2
9. 0
6.6
40.2
55.8
60.6
2. 0
68. 1
86. 0
11.2
46.4
130. 7       145. 6
9.2
16.9
20.3
46.4
0
12. 0
0
12.0
0
29-0
12.2
41.2
0
0
26. 8
26. 3CRITICAL RAINFALL AT MELKA WARAR
Date
Time
(hr)
Rainfall Intensity
(mm)
5. 11. 1965
0. 5
1. -
7
14
22. 2. 1966
0. 25
22. 8. 67
1. -
2. -
3. -
6. -
12. -
24. -
0. 25
0. 5
6
12 I
10
26
27
30
31. 6
32. 0
32. 4
12
23
34. 4                    1 35. 6                    /
~ 1
/lTable IC
CRITICAL RAINFALL AT AWARA MELKA
Elevation 905 m a.a.l.
D*le
Time
(hr)
Rainfall Intensity
(mm)
Date
Time
(hr)
Rainfall Intensity
(mm)
--—
|5.J|’45
|J.l964
0. 25
0. 5
17. 0
8. 8
12. 7. 1964
13. 7. 1964
11.2. >964
0. 5
6. 4
17. 7. 1964
M. 3. 1964
0. 5
1. o
1. 5
10. 0
20. 0
24. 0
6. 8. 1964
b. 4. |,u
U 4 1944
5 1944
”■5 1964
0. 5
1. 0
1. 5
2. 0
3. 0
4. 0
5. 0
0. 5
1. 0
0. 5
0. 5
1. 0
2. 0
9. 0
10. 0
12. 0
14. 0
20. 0
21. 4
27. 4
8. 0
17. 0
5. 5
2. 8
5. 6
7. 3
7. 8. 1964
11. 8. 1964
18. 8. 1964
11.9. 1964
05
0.5
I. 0
1. 5
2. 5
0. 5
1.0
1.5
0. 5
1.0
2. 0
6
24
1. 0
1. 0
0. 5
1. 0
2. 0
0.5
1.0
3. 9
2.8
4. 2
6. 2
10. 0
8. 5
15. 0
18. 0
20 0
30. 0
36. 0
48 0
57. 0
60
6. 5
7. 0
12. 0
15. 0
7. 4
11. o
12.9. 1964
1.0
20. 0
[**• ”14
0. 5
44CRITICAL ‘ A IT''/'Ll
(Maximum events)
Time
(hr)
Rainfall Intesity
(mm)
Station
0. 25
0. 25
0. 50
0. 50
1. 00
1. 00
2. 00
2. 00
6. 00
6. 00
12. 00
24. 00
24. 00
17
12
23
20
26
30
27
36
34
48
36
57
64
Awara Melk
a
Melka Warar Melka Warar Awara Melka Melka Warar Awara Melka Melka Warar Awara Melka Melka Warar Awara Melka Melka Warar Awara Melka Melka Warar
The following values were recorded at Awash August 1 , 1 966.
in   1   h   :   79   mm
"        2 h : 89 mm
"        3 h : 92 mm
(The representative
points of these falls areMINIMUM MONTHLY TEMPERATURE (°C)
Station; WON JI
Elevation: I, 540 m A a, \
1966
1967
1968
11. 3
8. 6
7. 6
14. 4
13. 3
14. 9
13. 6
15. 6
A 15. 0
15. 3
16.  9
15. 2
16.  3
13. 4
15. 5
15. 0 15. 5 16. 0
J
J
A
S
o
N
16. 9
15. 8
14. 6
13. 6
13. 9
15. 7
14. 8
15. 7
17. 3
18. 5
18. 5
16. 6
16. 4
17. 3
15. 8
16. 2
16. 6
16. 4
16. 5
17. 5
16. 8
16. 3
16. 0
16. 3
15. 3
16. 8
16. 9
18. 0
16. 5
17. 7
16. 5 15. 6
15. 2
15. 8 15. 0
- 16. 1
16. 0
16. 0
16. 8
15. 5
15. 3
14. 7
15. 1
13. 0
15. 5
15. 9
13. 5
11. 7 13. 0
9. 3 10. 0 11. 8
11. 7
10. 9
11. 2
10. 4
11. 2
10. 4
14. 1
12. 7
13. 4
8. 6
12. 6
9. 4
13. 0
D
12. 3
13. 6
11. 9
12. 0
14. 0
11. 3
9. 8
7. 0 7. 5
15. 8
- 15. 49
14. 18
14. 53
13. 91
13. 58 12. 88
Sou rca: AV A.MINIMUM MONTHLY TEMPERATURE (°C)
Station: METE HARA
Elevation: 955 m a. s. 1.
C.«-..Table M
minimum MONTHLY TEMPERATURE (oc)
Oeyation: 750 m .e.|
a
20.4
20. B
Average
19. 4J
IB. 98
19 97
19. Zb
IB. M
1? n
19 J5
|9 14
ie 7)
IB 56
19. «7
Mure t min refer. to 06.00 hour..
••••*** Suuon,MINIMUM MONTHLY TEMPERATURE (°C)
Station: DU B TI
Elevation: 370 m. a. s. 1. KOUC.LMU *•< K4C>Wr»-fX-. Y TJiMPmATUKE (“*■>
vrw                 a . \.
/ fear /
J
/F
/M
/A
M
(J
/ 1958
/     25. 2         /     27. 0
1 1959          /     26. 4            / 28. 0
I960
1961 / 26. 8
/ 26. 6
/ 26. 6
1962 I 25. 4 1  27. 6
1963 ' 24. 9 28. I
1964
1965
J966
1967
1968
25. 7
25. 7
2 6. 4
24. 2
25. 4
27. 9
27. 1
25. 6
27. 8
23. 6
30. 0
26. 4
27. 8
27. 8  |
29. 4
31. 1
28. 1
26. 4
28. 9
/      29. 5 /       30. 0 1     28. 3
1 28. 0
30. 1
27. 3
27. 9
28. 1
27. 4
28. 1
26. 9
30. 5
27. 6
30. 7
30. 5
27. 2
29. 0
30. 3
29. 6
28. 7
29. 9
28. 5
26 8
28. 5
28. 5
30. 1
28. 4
27. 9
30. 2
27. 6
28. 1
28. 1
J
24. 4
25. 6
24. 3
25. 4
26. 1
25. 2
24. 7
26. 8
25. 2
24. 2
25. 8
A
23. 8
24. 6
24. 7
25. 3
25. 3
23. 8
24. 7
26. 1
24. 5
-
25. 3
S1
25. 8
25. 7
24. 8
25. 9
25. 5
25. 9
25. 2
26. 7
25. 0
24 9
26. 4
O \
26. 8 1
27. 0 I
26. 2 1
26. 0
26. 0
27. 2
25. 5
26. 2
25. 5
25. 2
26. 5
N\
26. 4       \ 27. 2       1
25. 7       |
24. 1
25. 8
25. 6
26. 0
25. 6
24. 7
24. 0
D              \ Kvtr
26. 0 \
22. 5         \
25. 8          | i 24. 4              1 1 26. 0
24 8
23. 7
25. 5
24 9
23. 7
m \
\
27.02
26. 62
27. 18
26. 48
26 61
27. 20
26. 07
-MAXIMUM MONTHLY TEMPERATURE (°C)Tab*. 18
gyaUog; 750ma.il.
Av<r*jt
32 29 32.60 33.01 32. 70
32.2) 32.14
32 19
32. 19
’ ernPeratUr. dtu »M R.
*’*«*■ to | B. 00 hour.
R —^ch StatxonMAXIMUM MONTHLY TEMPERATURE (°C)
Elevation: 370 rn a. b. 1.
>—AVCHAGE MONIH1.Y TUMPEH-ATUM
<"C3)
AM
J
O
19. 60
20. 60
19. 50
22. 20
22. 00
18. 70
1966
1967
1968
18. 85         20. 00 16.40          20.55 16. 50          19. 25
127. 50 21. 00 21. 85
21. 45
21. 80
22. 90
20. 85 20. 00 22. 25
/ 22. 50            1 21. 05 21. BO             22. 60
22.45
22. 65
21.80
20. 65
21. 80
21. 20
21. 80
21. 45
24. 10
23. 70
21. 50
21.80
21. 95
21. 75
22. 20
2 3. 25
21. 25
22. 90
23. 50
24. 30
22. 50
22. 15
23. 75
21. 70
22. 15
22. 35
21. 00
20.  40
21.  45
21. 45
20. 75
20.  35 21.  55 20. 25 20.  50 21.  35
21. 30
20. 60
21. 50
20. 90
19. 70
19. 95
20.  95
19. 75
20. 70
20. 85 20.  40
21.  35
20.  50
20. 60
19. 95
20.  90
19.  00 20.  20
21.  15
20. 25 18. 95 19.  50 17.  65
18.  60
18. 65
18. 95
18. 20
18. 20
18. 45
Source Agricultural Re search Station.average monthly temperature (°C)
Elevation: 955 m*  * ’* 
a
Lr
Table U
AVERAGE monthly TEMPERATURE («c)
MA
M
1
J
A
S
0
N
—
0        Ave.-aje
21. H 1
25. 8
21. 8
26. 2
26 9
25. 0
30. 7
30. 9
31. 0
30 9
30 R
28. 9
28 6
29. 4
27. 8
26 4
27. 8
27 3
26 A
28. 1
28. 1
27 7
27.3
25. 3
23.8
25.5
25 2
23.9
24.1
24.4
22.1
22 2
21.9
22 1
25 44
25.7|
26 02
25. 76
23. 3
24. 4
25 3
24. 3
30. 2
28 2
30 2
29. 5
30. 5
29 R
27. 6
29. 0
26 4
26 7
26. 2
26. 4
27 5
26 4
25.8
26. 6
26. 3
26 3
25.8
26. 1
24.2
24 5
22. 1
23.7
20 R
21.2
22.4
21 5
25 )Q
25. 35
25.47
25 J?
?
3
3
4
25. 3
26 7
25. 9
26. 0
27 B
31. 0
29 0
29. 3
-
-
-
25. 0
25 7
26.0
25. 6
25 5
27. 4
27.6
26.8
26.0
24 8
24. 2
25 0
24 9
23. 9
22.0
21 6
21.0
20 2
21.5
20 9
•
•
-
0
6
0
9
24. 5
22. 3
25. 4
24. 1 Ave
28. 45
30. 2
28. 45
29. 0
a<v 1965
27. 3
27. 3
26. 4
27. 0
-196A pc
25. 1
26. J
27 0
26. 1
tod
27. 5
27. 9
27 6
27. R
27 0
25 0
24.7
25.6
24. 5
23 •
219
24. 1
22. 4
21.5
211
22. 6
25 06
24 69
25 2?
24
. 9
2
15
23J 4Q
26. 2              26. 3
26. 9              26. 0
25. 0               26 0
23. 3              26 1
24 4               26. 6
25. 3              27. 8
24. 3               26 8
25. 3               26. 0 26 7               26. 8
, 25. 9 25. 4
26. 0              26. 1
24.5               26. 6
22. 3               24. 7
25 4 26. 5 24. I 25. 9
23.7               26. 1
24 9              26 1
25 9              26. 4
24 M           26 2
26. 7
27. 4
28 8
27. 65
29. 3
30 1
29 7
29. 7
29. 5
28. 3
27 5
28. 45
26. 1
26. 3
26 7
26. 45
26 9
27.4
27 3
27.2
26 6
25. 6
24 8
25. 6
27 4
24 1
23 0
23. 9}
21 6
21. >
22. 4 21 77
25 73
25 57
25 71
25 59
i rn**_
• >«mpwraur« Tm la tho arithmetic rT”san ° UtC Rataarch Station.
00 ** 10 ’AVERAGE MONTHLY TEMPERATURE (°C)At inn ; MELKA WAXAK (Study Are*
Source : Agrtc. Research Station.
rMONTHLY RELATIVE HUMIDITY (%)
Swutc*-, A */A .
-
<l*.LMh'TKJLAKA
VAVDECADIC RELATIVE HUMIDITY (%)
Elevation: 750 m. a. fl. 1-MONTHLY HFt.ATJVfc mr
■TV <■*■)MONTHLY EVAPORATION (mm)
tation: WONJIV»
liblejo
KMONTHLY EVAPORATION (mm)MONTHLY EVAPORATION (mm)
Station: DUBTI
Elevation: 370 m. a. t.l.MEAN MONTHLY RADIATION (cal/sq. cm/day)I
0 HOc
1 607
0 fc9I
r
0 w
* nz
0 66f
0 957
0  izz
fl £tf
s
V
rr
FV
4 ■ fc k> □' WI-* I
■ 3) MniiVinvw AJKJMorw xrvrrrxMEAN MONTHLY RADIATION (cal/sq. cm/day)WIND SPEED (m/eec)o
i
cn
bu
»
X
E
3
4 a
x
a
j
5
i,
o
iM
*
5
-J
AVAWIND SPEED (m/»ec)
Elevation: 750 m a. a. 1.AVAMONTHLY VOLUMES (106 cu. m)
Aver:             AWASH jauging Station: KO KA DAM
Catchment Area; 11,270 aq . km
Observation Period: Nov. 1961 - July 1968
Year
1961/62 (a)
11962/63 (a)
11 963/M (a)
1964/65 (a)
N
63. 2
65.4
84. 6
I 93.7
Il 965/66 (a)                  83
D
80. 0
66.7
1 07.2
110.9
107. 2.
J
81.3
69.7
1 16. 3
112. I
111.8
Il 966/67 (a)
|l967/68 (a)
17 0. 2                       69                        66
160. 7
| 72. 3
69. 1
F
76. 2 67.6 92.   4
107.   3 116. 5
77. 1 68. 5
M
83. 5 97. 3 96.  8 97.  3
128.2
71.3
79. 4
A
65. 3
98. 8
75. 3
85. 5
97. 1
68. 3
75
M
71.5
83
92.  I
89.  3
87
63. 6
73. 4
J
67. 8 100. 1
99. 5 132
74. 7 62. 4
67. 1
J
77. 1
85.3
97. 2
98. 8 76. 3 60. 7 62.3
A
S
O
Total
74. 6
62. 4
77. 6
86. 9
113.3
57.7
-
63. 3
37
89 4
99. 3
112. 9
51.3
-
67.3
59.8
98. 7
88
107. 5
63.2
-
871.1
893. 1
1. 127. 1
1.201. 1
1.215.5
780. 8
-C2 uliihiik ■ ikl
-_n
¥/V  ‘  M  Mil  V< 1“ {•)6
MONTHLY VOLUMES (IO  cu. m)
River: AWASH
Gauging Station: METE HARA
Catchment Area: Observation Period: 1962-1968
Year
N
D
J
F
M
A
M
J
JA
S
0
Total
1962-63
1963-64
1964-65
1965-66(b) 1966-67 (b) 1967-68 (b)
61 (a)
83 (a)
98. 1
82. 5
73. 1
91.9
61. 6<a          50 (a) 100. 4 (a)       114.1 (a) 108.2             112.8 106.2             116.5
71.5               66.6 79.5              75.3
55.4(a)
92.5(a)
106.7
137.8
82.8
89 (a)
89. 2(a)
97.6
138.5
67.3
86. 3
121 (a) 103. 6(a
90.4
114. 8
78. 9
131. 3
139. 6(a) 93. 7(a 86. 7 88. 5 71.7
104. 3
95.4 (a )     108 (a
106.4
92. 1
65.3
92.9
)         109. 3(a, 132. 3(a 117. 5 138.8
96.5
110. 1
196. 6(a 200. 2 (a
156. 3
204. 3
141. 3
178. 7
150. l(a )       170.9(a
183
210
177.5
166.9
)        100.9(a) )        119.7(a
113.9
128.4
115
94
1,229.9
1,407.6
1, 377. 6
1, 558.4
1,107.5
1,211.2
Mama
Bo-cg FAQ
L
..
//,h’♦_**:* A. 7 A6
MONTHLY VOLUMES (10  cu. m)
River: AWASH
Gauging Station: AWASH
6
Mean Volume: 114. 4fl (IO  cu. m)
Catchment   Area   (below   Koka   Dim>7J00»q   km Observation Period: Nov. 1966-Oct. 1968MONrill V
VCJI.UM »-3 < I
Cnuh.u.ta Ar.> 1 . tow
QU»>rv»Uon V«TkutV. tHHX • t*>l»S
tern
J
J
A
Total
0. 4
45
0. 9
1b
0 8
5. 9
19 5
41. I
01
01
5. 5
3. 2
14 3
AVA
irwj6
MONTHLY VOLUMES (1 o cu. m)
Catchment Area: (Below Koka Dam);?, 300 iq. knr6
MONTHLY VOLUMES (IO  cu. m)
River: K EB ENA
Gauging Station: AVA STATION Year                    N                   D
Catchment  Area.  |t   245  sq.  km Observation Period: 1962 - 1968
1962-  63 (a)
6. 2
1963-  64 (a)             4
1964- 65 (a)
1965- 66 (a)
1966- 67 (a)
1966-68 (a)
10.2
22. 1
3. 3
28
4.6
4. 3
11.7
5.5
3.4
11. 3
J 11. 1
3. 7
11.9
3 (3.2)
12. 4
F
1.8
2. 5
6.6 15 (4. 9)
16. 1
M I. 8
5 6. 3
2. 8 15.2 15.4
A
10. 1
77.9
28. 5
4. 3
16. 1
M
1  15.6
12. 4
3.8
1. 2
(25. 6)
J
J
A           rs
O
Toul
32. 9                 23. 2
2, 8
15. 1
4. 1
1. 5
(4. 4)
19.2
41.8
96. 2
11. 4
12. 7
(18. 5) /
95.6
114. 7
130.2
93.7
1 35. 4      1 (H6.9) I
110.7  1
1
—
28                      4.8 50. 3               29.2 36. 2        I     26
3. 9        1       6.8 48                      5. 5 33. 2                  6.2
I
243. 3
430.8
250. 4
214. 2
265.0
404.2MOH THLV VOLUMr.'l (|Ofc
JT/y+r.1
OuhniwOt A«*fc lt**lOTr K<iU« Dau *. 1 4b„ 
Obi«rviiU&i\ p*r^od; VIhl - ''Jhlfr
»■*, Wk6
MONTHLY VOLUMES (10  cu. m)
River: AWASH
Gauging Station: SIL KILE
Catchment Area: Obiervatioa Period: »967 - 1968A
>
MORtif] Y VOLUMES [it** cm. ml
^v*r: AM'ASJ/
gju/f 4ajf .■JStaftoa; JiERTAi-£
x.t «» OburvEUon t*«TlQd-. 44bi - l4bb
far
N
D
J
F
M
A
J
J
A
S
O
Total
(120]
(70 0)
{70)
81 1
2 37, 4
28&, 7
117, 4
2 38. I
579 9
376. 4
110 3
2, 371. 4
122, 3
142. 1
149. 7
121. I
108. 7
14J, 9
115 9
132, a
435. 6
5BB 9
442, 4
209 7
2,711, 1
J12. 8
147. 7
116 I
1)6 9
151. 2
98. 4
103, 3
123. 8
396 a
329. 6
172 7
1,994, 4
1966-67
75. 4
76. 2
69
72. 0
104 2
112
141. 2
60 6
17. )
47d
428 0
268 2
1,9<H 7
1967-68
87 9
8). 9
137, 5
119 7
20 J. 2
153, 7
106. Z
284. I
522 5
331 9
151. 4
J,156 6
I-
±._
I?*| 
Dully valtf
t*.
y* JfUt AV A,
wl6
MONTHLY VOLUMES (10  cu. m)
River: AWASH Gauging Station: DUBTI
Catchment Area 63. 865 sq. km
Observation Period: 1964 - 1965
Year
N
D
J
F
M
A
M
J
J
A
s
0
Total
1964-65
144. 4
(591. 5)
(100. 9)
(81. 5)
(116. 5)
(201. 0
(112. 8
(71.3)
1 (81.9)
(320. 5)
(242. 3
(180.4)
(2. 045. 0)
'I
1
1
1
I
1
1
l
1
1
1
1
/
SQMrca; AV A.6
ANNUAL VOLUMES (IO  cu.m) (AWASH. KESSEM AND KEBANA RJVERS)
1 Hydrological
1  Year
1 Awash at Kaka       j Awash at Won Ji
Awajh *l
Melcbara
' Awaah at Awafh Station
Kesaem at Awart Mclka
Gauging Station
Kcbena at AVA
Gauging Sutiun
Awi*h at Hartala
1961-62
1962-61
1963-64
1964-65
1945-66
1966*47
1967-60
Avirip
(&06 c*«. m>
an. i
S9J, i
1. 127. 1
1*201. 1
1.215.5
7BO. *
•
1. 014. ■
-
-
-
•
1.404. 9
1. 061. 5
la ia». 7
1.229.9
1. 407. 6
I. 577. 6
1. 55t. 4
1. 107. 5
1. 21 1. 2
2. 571. 4 71 L I
I. 994. 4
L 1^*
1. 2 4 9. 7
i. in. 4
-
1.647. 0
1.895. a
1.5 30. 4
1. 7H0. 6
1, Jt7.2
1. 4 10. 2
I. tiru. 2                  j
•
-
649.4
lit. >
624. U
5 17. 9
141. 5
1*0. 2
243. 3
410. M
250. 4
2 1 4. 2  1
269. 0
404. 2
101 >
l
_
 1OaerMpaham
******
Awa.h .1 Kaka
*•••* • • Malabar*
Awaah •• Awaah Matiaw *»ba al Atka
Kwhaaa
Awaah •• Martaie
Awaah al Kaka
Awash el W aaQ| Awaak al Malabar a
A»aak at Awaah Matin* Arba ai Aria
Kaaaam al Aaari Malha Xakawa
A.aab al Hartal.
Awash at Kaka
Awaah al W<aaj1 Awaah al Mrirhan Awaah al Awaah Slrtlw Arte, at Arba
Kaaaam al Awara Malka Xehaaa
Awaah at Hartale
I
Awaah at K-iteh
Awaah at Wosjl
Awaah ai Mat aha re Awaah at Awaah Stallaa Kaaaam al Awara Malha Kaba&a
Awaah at Harthle
19bh-fc7
Awaah al Kohs
Awaah at Wonjt
Awaah at M Mahar I Awaah at Awaah Stattoa Malha SaAl
Kaaaam at Awara Malka K »b»M
Awaah at Malha Warar Awaah at !tl|hUa Awaah at Hartale
111.9 I.
K
ii
•>
■9.1 M. »
•K T «. T
11. 1
•
!•?. 1 (9K
IM. 1 IM. ■
1. 1
». s
-
I1U.I1
I IM. M. I
IM. t
I'M 1)
(Th. t>
Woajl
M Mahar a Awaah Statlaa
Awaah at Koha
Awaah at WonJI Awaah at Matehara Awaah at Awaah Matioa Awaah at Malha 9a41 Kaaaam at Awara Malha Kabawa
Awash al Malha Wafer Awaah at Silbile Awaah at Hartala
(IK IJ
lit » Th. t-Ji
J
£
aMONTLHY SEDIMENT LOAD OF THE AWASH AND OF THE KESSEM RJVERS,(1965-I966)111 ‘tit >
m *hi
iu m
-
Ml 11
itu *0H
•i£%i
**i +m
?L0 >17
1 M>*»iT
1.0* 'ttfr’l
■1 r. >tr
m >11
HL 'S«8
»11 It
i m>v
111
tzs'tz
Ofr'SI
mi *7
6W1T
fafeR'E'I
ii^’r
WHC
orz'o?
flll’l
It* 1?
Z*D*5t
*10 >
IZf > t
5«’l
EZ* '07
m  fi
*<1*H VlBMY
uauriS H”*¥
r
4«*l
(it? 'ST
01*'Cl
(ii'i ' ,      00*'1T
!*«*■»
......p.
H ■ »*¥
M«"V
1 iw
y
V
M
j
r
a
X
uspittg fcriinwD
J*A]y
L
p
1 rt
£■ U'OI Dll
UH I" JW II 'H3AW'K3SS3M 3HX JO 3«V HSV.UV 1W1 JO JV01 imWTOSS XTHXXOHWATER ANALYSIS AWASH AT AWASH STATION
Date
H
(m)
gr/l           C (
Uvity
17.4.1963
2.5.1963
9.5.1963
11.5.1963
15.5.1963
2. OG
3. 37
4. OO
4. 37
4. 26
5. 2
5.9
11. O
15. 1
5. 3
^12.1963
2 1.1964
9.1.1964
11 1.1964
16 I 1964
18 1.1964
24.1.1964
tracei
17.5.1963
18.5.1963
19.5.1963
20.5,1963
21.5.1963
22.5.1963
24 5.1963
1.6.1963
4 6.1963
5 6.1963
B. 6.1963
19.6.1963
1.7.1963
3.7 1963
5.7.1963
15 7.1963
16.7.1963
17.7.1963
18 7.1963
23.7.1963
29.7.1963
2. 8 1963
12.8.1963
14.8.1963
16.8 1963
21.8.1963
22.8.1963
27.8.1963
25.111963
27.11.1Q6J |7 12.19631
10 12.1965
1 32
10 1.1966
1 14
tracei
0.24
7.1
24.2 1966
1. SB
0 S
0 20
7 1
25.2 1966
2 69
13.2
0 24
7.4
10.3.1966
1. 11
trace!
0 S
11
15 4 1966
1 65
5.5
0.6
’3
21 6.1966
1.04
trace!
C4
1 7
13. 8.1966
I 70
trace!
1 I
24 2.2965
1. 17
0. 1
0.4
1.2
30 9.1964
I. 39
tracei
7.4
7.10.1964
1.7B
tracei
*4
13.5.1964
27 6.1965
1. 26
I 38
8. 6
tracei
27.7.1965
1.08
0. B
23.8.1965
1.47
0.6
7.9 1965
1.47
0.5
0 24
•s
10.12.1965
1. 32
1.3
0. 24
7 3
10.1.1966
I. 14
tracei
25.2.1966
2.69
13 2
0 25
tracei
0.H
•1
18.9.1965
1. 68
0 I’
7 •
7.10.1965
1.75
tracei
7 1
0. 26
1. 30
tracei
0 19
0. 23
20.1® 1965
0.3
7 *
20.2.1967
1.20
0 3
0 3
8 •
0.
1 H
0.4
25.4.1967
0.2
0. 27
28.7.1967
1.52
0. 1
0.2
0 1
traces tracei
0. 2 0 3 0. 2 0. 3
0. 27
7.B.I967
1.48
0 24
1.58
0.3
5
0 3
0. 23
9 8 1967
11.8.1967
2 30
1.3
0.2
0. 23
2.40
1 <
5.2
0.5
0. 25
0. 26
1.52
1. 04
1.42
12.8.1967
24 2.lq88WAT EH AKALTKs KE5SEM AT AWA»A MXUa
Gandhi r -
llvJty frnmhca)
0. 40 0. 41
a. is
0 44
r 3**Air-
n.i
t 10. 1?4J
Z. 10
J  10  IUJ
1  10.  !HJ
4 IQ. 04 i
< 10 iHl
’n^l
tfiui
>INI 41465
II  M3 ft i. IHJ Ji  IHl 4i:m
<1 'Uj IHd
•Ml^j
2   Him
*i iHj
V
'‘ M] M  ’Hj J|  ’H)
7 5
7. 7
7, 7
7. 9
7 7
7. A
7. 1
7. 7
7, 4
a 1
7. 9
7, 0
7. ft
7.7
7-9
7. 9
7.9
a. G
3.0
3. 0
8. 1
8. 1
8. J
7. 0
«. 1
ft. 3
8, 3
6 J
H. J
fi 3
8. 4
n mi
It   B6J
U 1HJ
It l96j
U-L 1741 i 9 JJ 3 4. B45 0 w 1 4. IW 1 rt 7‘
■ric»>
■Firm
r r»rea
t«Cf#
Tnri
I ,'i
'-7
j 3- 1ft
&&
11-
30 5 1943           J. 63         ifiet■             1 «3       •
3 1.1              f
1
i :j       1   4 .
26 t IH5
1
| Q ?< j
1 * *
J SJ              4 4
j a ms
IL B. 1945
20 a 065
2 9. 1945
5 11 1464
’•«     I* S     1    5 25              T 4 1 5J     •   7 *T         ■« ».■*
! 5!
L i
j S 16             7 •          -
1. 17 20
, ■ h | Iracvt
:.n
i
9 li 1465 ' 0 77
14.2- 1966 1 a,«
1
0 4
3 24 - ’ i
2 JI       1       4 i
3 If                  * i i
21 9. ms
,n
tti€M              i t r          1 -,
29. 9. B65            3 4i    ferae t®
’-
1. H ‘-*2 *■26 1 U
1 K
5. 10 1965           0 IS 1ft 5. 066             0 B t5. i IU6             0. 71
U 4. IM              0 65
4. 8. IMS           2 -92
5. ft. 1966
6 ft  B66
r
Fr*SL*«
so
9 27 1 -L
:?>£«■ I. «
!r«c<v 3 W
’'1
1 ’ J
1 1
33 5
:i ft
*». 2-2
210 |
7. ft 1964       |   203 I          a?
0.2 ****••
S. ft. 1966
fl.ft.1966
8.6 Bit
9 a. mi
10 ft. 1966
5. 9 19*6
t Il 1966
JI. 7. 1 »67
1. ft. IH7
1 ft. 1967
! 66
3 U
'» i
» ’ 1
tTtrri
it> 1 se«e««
143  1 iriiai
1.47
OH
l.M
103
Irtff* '
J “ 1
1
;*
1 7 ft
■’ I
? 7
-
■*
7 t
•s !
• * l
tr«c««            a. b3 ,         7 *
Li              £
T1
l.U j         n «
'‘ I 3. 13 70
BM              TO
iWATER ANALYSIS
KEBENA AT AV A STATION
Date
24. 5. 1963
27. 5. 1963
1. 6 1963
12. 6. 1963
12. 6 1963
I 3. 6. 1963
14. 6. 1963
14. 6. 1963
23. 6. 1963
24. 6. 1963
Conduc
tivity
(mrnhoa)
PH
10. 6. 196 3
22- 7. 1963
24. 7. 1963
25. 7. 1963
26. 7. 1963
27. 7. 1963
28. 7. 1963
29. 7. 1963
30. 7. 1963
31. 7 1963
1.8 1963
2. 8. 1963
3. 8 1963
4. 8. 1963
5. 8. 1963
6 8. 1963
H
(m)
0. 39
0. 35
0. 30
0. 30
0. 26
0. 27
0. 27
0. 34
0 30
0. 26
0 26
0. 28
0. 59
0. 64
0. 96
0. 88
1. 20
1. 06
0. 82
1. 96
2. 56
1. 14
0. 96
0. 86
3. 52
1. 62
I. 40
Rr/l
trace*
trace.
-
-
-
-
•
0. 1
-
-
-
-
0. 4
0. 8
9. 4
1 3
8. 5
14. 8
trace*
19. 6
28. 8
0. 4
1. 6
0. 1
16. 7
49. 6
4 2
Conduc-
tivlty
(mmhoi)
0 31
0 24
0. 25
0. 25
0. 25
0. 28
0. 25
0. 21
0. 26
0. 24
0. 22
0 22
0. )8
0. 20
0. 20
0. 21
0 16
0. 19
0. 18
0. 16
0. 18
0. 15
0. 1 3
0 16
0. 17
0. 17
0. 15
0. 16
PH Date H
(m)
8. 5
8. 4
8. 3
8. 3
8 2
8 1
8 4
8. 3
8. 2
8. 2
7. B. 1963
8 8. 1963
* 10. 1963
1. 20
1. 06
0. 48
14 11. 1963            0. 48
>5. 11. 1963
26. 1 1  1963
27. 11 19fcj
0. 47
0 44
0 44
10 12. 1963           0 48
11 12. 1963           0. 48
11. 1. 1964             0 48
8 0                   27. 1. 1965             0 48
8 4
7. 8
7. 9
7. 8
7. 5
7. 6
7. 5
7. 6
3. 4. 1965 0. 48
JO 4 1965             0 35
511 1965              0. 46
9. 12. 1965             0. 51
111. 1965 0. 47
21 9 1965 0. 59
28.9 1965              0. 50
5 10. 1965        i 0. 69
8 2                   19. 10. 1965           0. 55 7. 5                   12. 3. 1966             0. 48 7. 8                   25. 6. 1966             0. 45
19. 4. 1966 0. 70 7. B. 1966 1. 63
12. 10. 1966           0. 62
I. 12. 1966             0. 58
26 4. 1967              0. 60
0. 4 trace.
’race. trace* trace. trace* trace. trace. trace. trace. trace. trace. trace. trace. trace. trace. trace. trac.a trace. trace. tract.
trace.
trace. trace.r
FIELD WATER REQUIREMENTS
(l/sec x ha)
Months
Nura Era
and Tibila
Melehara
Abadir
Others
January
February
March
April
May
I     June
j J ul y
1 Augunl
1 Supl timber
Ocl ob« r
1    Mu voi Tiber
| IJniarnbnr
0. 18
0. 40
0. 40
0. 31
0. 04
0. 31
0. GO
0. Hb
0. 9H
<h 74
lb 56
<J. 10
0. 61
0. 62
0. «4
0. R5
0. 9 5
1. 07
1. 00
0. H5
0. H2
lb 74
O. 65
I*. 56
0. 08
0. 08
0. 12
0. 12
0 I 3
0. 46
0. 62
U. B5
I). 9H
0. Hl
0. 61
0. 2 I
0. 18
0. 40
0. 40
0. 31
0, 04
0. 31
0. 60
0. 8H
0. 9H
0. 74
O. 56
0. 1 0WATER REQUIREMENTS UPSTREAM OF AWASH STATION (cu. m/sec)
Month
i
Nura Era Metehara Abadir
(cu. in/sec)
(cu. m/sec)              (cu. m/sec)
Others
(cu. m/sec
Total             i
1 (cu. m/sec)
January
F ebruary
March
April
May
June
July
(      August
( September
1 October
\ November
Occe muc r
1_____
1. 17
2. 60
2. 60
2. 01
0. 26
2. 01
3. 90
5. 72
6. 37
4. 81
3. 64
0. 65
4. 88
4. 96
6. 72
6. 80
7. 60
8. 56
8. 00
6. 80
6. 56
5. 92
5. 20
4. 48
0. 32                      0. 14
6. 51
0. 32                      0. 32              I        8 20
0. 48 0. 32
0. 48 1  0. 24
0. 52 0. 03
10. 12
9. 53
8. 41
I. 84
0. 24                      12 65              1
2. 48 0.48  ( 14. 86
3. 40  , 0. 70  I 16. 62
3. 92                     0. 78
i 7. 63             1
3. 24            1       0. 59                      14. 56
2. 44                     0. 44             /       11. 72             / 0. 92                           0. 08 /
6,3  k
Source Inception Report, page 134
------ :F7XI-D IKRTCATIUN REQUIREMENTS IXJK ill DAK 1-ElUOMi
(jn I/ivf/MJ
Vr»KrrMAXIMUM BCQU1BKMKMT0 FOB KA CM TKMDAY
D»«« elpUan
ill
Crawlee
<*>
Field
■ »td remente
(t/eec ■ ha)
(•>
tbe Diver elan
Wat*
(l/ee< . Ha)
at
(')
Q
■
Tata J
■ e^et ramenta
I'M. m/*«)
Jtwaxi
1st decade
2nd    decade
ted dacada
F efrruati
1 al darada
A.  1
0.  34
l» 1                                 0 41
•  41S
0 440
9 440
3 7. 900
17.000
B.  2
Sett A
0 41
7. It
4 13
0 31
V»ctr».R M Awaeh >a«ea l»ae Ta Ma 44)
!»*• te/eet|
9 S|
9  SI
A 91
m
T-a* '"•■'ml
11 74
14. 04
IS 04
I.WS.1X
1
• 41
0   440
It OS
2nd 4erH.
Salt. A
0.  99
«.     ns
17.040
19   U
11. >3
» 449 Ml
trd decade
Sett A
S. 99
o T2S
17.OOO
».St
it. >i
10 St
M-rxh
l«t decade
2nd decade
Jrtl darada
A&r > t
la* decade
f nd darada
ltd decade
Sett    A
Sell. A
Sett A
0. 73S
9. OS
0 SY
0 ’40
® SIS
9 s>o
17,400
17.000
11.044
13 43
IS 40
IL 41
0. IS
0. IT
0 475
9. 459
0 32S
If It
19 l|
10 II
9 St
9 St
9 St
11 M
1A9I
19 St
ItXT 91*10
' ms tn
Sett. B
Salt It
Sett fl                                 0 23
• SO
T. 74
B.S1
• 7 41
It.   |9 IS M
let decade
J^ny
Idt derade
2nd decade
3rd dacada
Jul>
let decade
Sett. B
0 11
0. its
17.900
17.000
17.000
17,000
9 oi
9 41
IL 14
:.Ul Be 1.910
•.■•.IM f tv r*
B. 2
Sett A
Sett. A
0 OS
0 XA
0. 24
0 IBS
0. ISO
9. ISO
19.000 1
17.000
IT. 000
3 IS
5 9S
S OS
19 9S
IL  4»
IL AS
19 M
It M
19 40
t »*.«
Sett. A
0. 2A
0 ISO
IS.ooo
S os
Id 44
19 41
I.’T     *•
it rd darada
B. X
0 1Y
0. 390
IT. 000
9 II
14 04
IB. 44
i. Bi9 n
ltd decade
Sett. B
9 13
0. JiS
17.900
1 S3
14 44
M >4
l.*M Ft
d^Otl
■ at dacade
2nd decade
3rd decade
September
la* decade
2nd dacada
3rd decade
October
lot decade
2nd decade
3rd dacada
B.  Z
0   os
B I                                     0 20
B2
0 37
0. ISS
0. 170
0. 4SS
17.000
IT.000
17. OOO
1M
4. XS
t. to
19 42
19 U
19 42
IX St
19 14
Sett. A
0 A?
Sett. A                                 0 11
l.»S.9t t.n* XH9W
L<9
L**
9*MM
Sett B
0. 730
0. 090
O. 919
I?  41
17.93
0. B?
17.000
17.000
It. ooo
IL 41
19 91
IS.M                            17 93
39  04 IL U 31 It
Sett B
AI
A. 1
0. •?
0. 94
0 19
0. SIS
O. 990
9. 900
IT.ooo IT.000 IT.OOO
IS S4
It 13
IS so
19 M
I9M
19 M
M 11
IB ••
n so
ttau-
lMAP*
xrs*
let decade
2nd decade
3rd decade
Ot camber
lat dacada
2nd dacada
Ird decade
AI
0. SA
0. SOS
A I                                      0 20                                  0 197
Il n
ii.    n
II. n
n    ii 19 n ii ”
L** I.*” tF9*
A. I
0. Al
0 902
IT. 000
IT.000
IT.000
IS. H
SOS
10 13
A. I
0. 31
0. 12
0 4SS
0. JIS
o. ISO
11.009 IT. 000 11.099
T. 74
SM
9 S3
A 19
9 13
ill*
It*
Ll<“*
B 2                                     0 30
The mcdrauw repair amenta have been cnaaidared for each decade at theCOMPARISON BETWEEN HIWGATJOK DEMAND* ' I ANO TUX JUTOAL FLOWN OF THE AWAW.^ESJO,* AHO KUCHA RTF CM
IK tt.sl
0 Sea Table 67,      cotamn 8.Demand
Natural Flow* Ke«>ern                                 Keheria
h.
2nd decade Demand: 2. 248. 1 28
13.  3.  1967
1.900.800
14     3.  1967
1.900.800
15   3.  1Q67      2, 376. 000
16.   3.  1967
17    3.  1967
3.  1967
20    3.  1967
21.   3.  1967
2.      004.480 2,695,680
i   .   866.240 2.   073,   600 1.969.200
*234.144 217.525
- ,28.346 -H5.715
22.   3.  1967       2. 246. 400
3.  1968 20.   3.  1968
’1.52;
1 • *63. 840 2.574.720
47.520
47.520
47.520
47.520
94,  090
95. an
69.I20
64.8Q0
64.Roo
155,520
139.968
518,816
305.056
April (no deficiency)
May
2 -0»3.9R4 2.     030,57j *•516.832 *•189.782
276.431
2.082,413 2-258.140 *•457, )60 2. 769,984 2.038, 176 3.020,544
-209,95>
2nd decade Demand: 1.607,040 3rd decade Demand: 1,607.040
18.  6   1968
1.421.280
none
22. 6      1966
23    6   1966
2 4.  6   1966
25.  6   1966
26.   6.  1966
28,   6.   1966
1.516. 320
1.278,720
I. 183. 680 1. 326.240
1.2 31.200
I . 563, 840
229.824
648.O00
756.000
900.000
328, 320
397.440
394.440
<no deficiency)
June
544, 320
50.112
50.112
50,112
56. 333
62.554
59,443
■July (no deficiency)
Auguat (no deficiency)
September (no deficiency)
2, 195.424
2.214.432
2.084.832
2. I 33.792
1.710,891
1.691, 194
2.017.723
r.or.e
none nor.e none none
tore
ITlhl g lift i Carl. 2,
rj.p->u
feficit
3 is I ii n = h
Pc igg* f
16.  10.  l*?67     z,55j. Jan
I?.   10.   1^67 ja, 10, 1967
2. 004. 480
2,799. )W
19   ID 1767        Z. 551.120
20  10. 1767
11, ID. 1968
12. 10. 1963
1 J, 10. 196ft
14. IO, 1963
2,112,300
2.410.560
2,555. 040
2.410.560
1.944,009
15.    10  1968      1.421,280
~lrd dec-j.dE Oeffljind: 3,. 579  9O'!
F
16- 10. 196ft
21.   10, l«?67
22.   10 1967
2 3. 10. 1967
24. 10. 196?
25. 10 1967
1.9*5,040
Z. 16a, (JOD 2. 289.600 2, 332,ftOO 1.728. ODO 2,462.400
26. ID. 19 67 I,831,630
27. 10. 1967 2.289,600
2ft, 10, 1967
2. 116,800
29.  TO. 1967      2.417,200
30. 10. 1967
31- 10. 1967
2. 505,600 1. LOO.240
51ft,StB
504.144
446.432
468,720
151.035
7^3,600
959,040
959.040
933,120
S98.540
895360
433,2^6 415,584 397,472 J8O.165
330,160
367.200
367.200
J67.20C
367.200
367.200
341.250
41,77? 41,77? 11.779 41.77? 47,601
131.536 171,916 J71.9J6 171,936 161.5tl ltl.566
K3,1d4 773.464 17 5. 164 173.464 573, IM 37 MM 171.464 37J. tM 173.464 373.464 173.461
2,414.467 2.550,401 J. 127,571 M6J.6I9 2.8*1,414
1.597,  6U 1,356.016 I. 541.536
3.049,056
2,461,440
3,055.968
2,466 760 3,0TB,64* 3,104.136 2.451.624 3,216,524
2.572- 144
J, 030,264
2.857,464
Ms?, m 3,246,264 I.814.994
- 14,813           ’   14,813 <47. 542
- tJJ St*          * 8 5.408 *406. ?44
- aji.jS ■
. 7,56?
-    59.280 *537. M3
7,5^0
•442.^3
Nd'/e ~_Natural Flow*
I                 Demand
D.itc
Awaah
Keaaem             [       Keb ena I
Total
Deficit
November (Cnnt. )
6. 11. 1967
7 11. 1967
2. 003. 200
1. 373.760
1     354.240             i
351.994         1
1       367.200          1     407.462         1
8 11 1967 I 1,753.920
9. 11 1967 I 2. 358.720
10 11. >967  ' 1.553. 920
1      354.240          I
333,504         1
1  341.280  1 319.507  ’
1  341,280  1 >33.504  |
Z.909.434  1
2,148.422
2.441.664 1
3.019.507 j
2.428,704 1
-191.862
II. 11. 1967               2.358.720
1    415,584
425.952        |     3.200,256
12. 11. 1967
13. 11. 1967 
2.255.
4. 190.
14 11. 1967               6.989.7
3rd decadr Demand: 2, 579, 904
22. 10. 1968
1,944, 000
1    451.008             11.192.320           1    3.898.368 3    1    581.472             12,488.120           1   7,260.192 0    1    605,664             12,125.440
October 11968)
1
11, 166. 400            1     139.968         1    3.250. 368
2 k 10. 1968 2,799,360
24 10. 1968 3,412.800
11,028. 160 1      139,968
3,967,488
1    933.120
1 39.968 I              4.485.888
25.
2.410,560
1    777.600             I     1 39.968        1      3.328.128
26    10   1968           1.944,000
1    777.600
139,968         1      2.861,568
27.   10.   1968
28.   10.  1968
29 10.      1968
30. 10.     1968
31. 10. 1968
1.753.920
1,944.000
1,231.200
2.047.6B0
1.896,
1    803,520              1    129.600                 2.687,040
803,520           1     129.600 803, 520          ’ 118.168
777.600 1  118.368
2.877.120
1   2.153,088 1
2.943.648 1
426,816
725. 760
118,368        1   2.740.608 j
October (1 *>64)
-42MU
- 63. fl
. 07.612
27. 10. 1964
2. 380.408
583.ZOO
462,931
October (1 965}
3.426.539
3rd decade Demand:2.579. 904
10. 1965
25.
10. 1965
26.
27.   10 1965
10. 1965
28
10. 1965
29.
10. 1965
30.
10. 1965
31.
1.706, 400
2,743,200
2.574.720
2.462.400
2.574.720
2.462.400
2.574.720
110,592
96.768
96.768
86, 400
86.400
76.032
64.300
333. 504
333.504
333.504
333.504
333,504
333. 504
333.504
2.1*0,496
1,171,492 I
1,004,991 |
2.812.104
2.994. 62*
2,871.916
2,912.*24
-42’.408T_»ble 6j CGofll U.
D-it*
nrrr»*nd
Awdih
K*a lea
Flo«v
1
j 2>be=ji Toni
I
nher (1U5)
I Deficit
L—-
B* La nee
f—------------- —
>r-irltfofa z. M».504
]. 1 1. 1^65
i, I!, l^5
3. II. 1965
4, 11. 1965
5. H 1965
6. II. 1965
T. 11. 1945
281,920
198.720 181,440 151,200 136.512
151,200 L 332.000
100,129
1116.53!
117,936
n: m
r
100.829
Z56. W5
2.515.949
1.774,051
2,453.736
L 547.156
2.596,061
J. Bl.001
-568. 251
-7-34 44B
1
?,, 30 J. 200 I. 166.800
2. 151, 360
1.270,720
2, 358,720
2.743.20U
2,749, 360
2,462.4O0
2.743.ZOO
2.462.400 2, 462,400 2.266,040 1.649,960
4, 496, 326 ' B. 577.636
CktubjS (hhi
-568.251 -459.821
-t.2M.269 -t.000.512
-191, 80S ♦8, 305, 878
‘rd decade
^manH 2, ’’7% 904
26. 10. i 66
a
27. 10. 1966
28, JO, 1966
29. 10. 1966
30. 10. 1966
31. 10. 1966
367.200
167,200
367,200
367,230
J67.ZAO
MjZK
241,920
241.920
3,071,5’D
J, 352, J 20
211,650
J, 041,260
181.443
1,911.040
IS!. 440
2,403,6411
151,200
2,341.44*
-231. 464
-23B,461
■Vox-fTllfe* » fl«66\
c jj,de
j 4iw 5Q1
I- 1 1. 1966
2- 1 !. 1966
3. 11. 1966
4 It 19M 5. 11. 1966 6- I J. J966 7. 11. H66
1,797, 120
2, 203.200
t. 935.560
1,650.880
2. H6. m
Z,246. 403
2.210,SOD
341,200
354,240
354, 240
167,200
154,240
154,240
367. 209
128,960
i’0,960
120.969
r20.960
120. 963
10% w
109,300 jfofrfjnbljr
2,259, U0
2,678,400
2.410. 760
2.147.P40
l.M2.0:D 2,710,540
2.687, 9D0
(!1M)
- 62.944
-195. 2 64
-121.404
* 14.688
*195.264
• 54. 4 12
1   11. 1964
i-ll. 1964
5- U. 1964
*• ii. m«
J, )92.979
3. 171,877
2,450.939
1.675, 1.10
619. 369
609.120
409 120
+
fcO?.12D
407, 462
425.952
jSt.96’
340,462
2,43% B®1
4,283,949
3. 44% 021
2,673. |S1
1
IfortmUr (T9fr51
^1
‘ <4r-9Z8
1
1
1
1
1
ey)
1 1n>tr
Awash
November 11 962)
3rd decade Demand: 1 . 896. 4B0
1
25. II. 1962
24 1 1. 1962
25 11.1962
26.   11. 1962
27.     II.   1962
28 11. 1962
29.   11. 1962
30.   1 1. 1962
1,756. BOO
1.728.000
1.641.600
1.641.600
1.267.200 1.641.600 2. 246. 400 2.217.600
no data
no data
no data
no data
no data
107.827
107.827
107.827
107.827
107.827
no data            1     107,827
1.864,627
1.835. 827
1.749.427
1.749,427
1. 375. 027
1.749.427
2, 354.227
2. 325.427
- 31.853 ’ 60.65) -147.053 -147.053
•521.4S1
•147.053
no data
no data
107.827
107.B27
- 31.353
• 92.506
-2 19,559
’386.612
-908.065
•I.D55.1U -517.J7J
1    -168.424
December (1962)
1st deiadr Demand 1 . I 98, 368
1.   12.   1962         2.       131.200
4 12. 1962
5. 12. 1962
6 12. 1962
I.036.BOO
1.152.000
1,929.600
no data
no data
no data
no data
2nd decade
3rd decade
107.827
86.400
81,561
81.561
no deficiency no deficiency
2.239.027
1. 123.200
1.233. 561
2.011.161 1
75. 168
<827,2)5
-   75,163
-     '9,775
-•772,818

< <

Summery

Summary: Melka Sadi-Amibara Irrigation Project Feasibility Study

Melka Sadi-Amibara Proposed Irrigation Project Feasibility Study

Volume I: Hydrology and Climatology

Prepared by: Italconsult for the Imperial Ethiopian Government, Awash Valley Authority

Date: July 1969

1. Introduction

This document presents a feasibility study for the Melka Sadi-Amibara Irrigation Project in Ethiopia's Awash Valley. Volume I focuses on hydrological and climatological aspects, providing critical data for project planning.

2. Key Findings

2.1 Climate Characteristics

Temperature: Mean annual temperature at Melka Warar station: 25.6°C
Rainfall: Average annual rainfall: 576 mm, with two distinct wet periods (short rains Feb-Apr, long rains Jul-Aug)
Evaporation: Highest evaporation occurs March-July (up to 376 mm/month)
Climate Classification: Semi-arid bordering on arid (Thornthwaite water index: -37.19)

2.2 Hydrological Data

River	Gauging Station	Catchment Area (sq km)	Average Annual Flow (10^6 cu m)
Awash	Koka Dam	15,250	1,014.8
Awash	Awash Station	7,300	1,713.5 (1962-66)
Kessem	Awara Melka	3,135	590.2
Kebena	AVA Station	1,245	301.3

2.3 Flood Estimates

Location	100-year Flood (cu m/sec)	1000-year Flood (cu m/sec)
Awash at Awash Station	900	1,175
Kessem at Awara Melka	1,200	1,450
Melka Warar (project area)	1,539	2,009

3. Water Availability and Irrigation Requirements

3.1 Water Balance

The study analyzed water availability versus irrigation needs for a 6-year period (1962-68):

Significant water shortages would have occurred on only 3 days during this period
The Melka Warar weir's reservoir (650,000 cu m capacity) could mitigate most shortages
Recommended minimum discharges range from 13 cu m/sec (May) to 34 cu m/sec (September)

3.2 Project Viability

The study concludes the irrigation project is feasible provided:

Cropping patterns and water requirements remain as planned
AVA maintains control over water allocations
Koka reservoir operations follow established patterns
Minimum discharge requirements are maintained

4. Key Recommendations

Implement the proposed irrigation infrastructure with two diversion weirs (Melka Sadi and Melka Warar)
Establish water management protocols to balance upstream and downstream needs
Monitor water quality and sediment loads in the Awash River system
Develop wells to ensure water supply for local inhabitants during low-flow periods

5. Study Limitations

Limited observation period (3-6 years for most stations)
Some data inconsistencies between different measurement methods
Need for ongoing monitoring to verify long-term hydrological patterns