2)
Ethiopian Electric Light & Power Authority
Aleltu Hydroelectric Project
Reconnaissance and Prefeasibility Studies
Volume 1- Executive Summary June 1984
n
Acres International LimitedVOLUME 1
VOLUME 2
- EXECUTIVE SUMMARY
-    MAIN REPORT
VOLUME 3 - APPENDIXESJuly 19, 1984 P6888.0 3.0 1 
.03.02
.04.01
Ethiopian Electric Light
and Power Authority
P.O. Box 1233
Addis Ababa
Ethiopia
Attention:               Ato Tamene Wolde Yohannes
Manager, Planning and
Programing Department
Gentlemen:                                                      Aleltu Hydroelectric Project
Reconnaissance and
Prefeasibility Study
We      submit      herewith      the      final      report      on      the      above      study      which comprises the
-    Executive Summary, Volume 1
-    Main Report, volume 2
-    Appendixes, Volume 3.
We wish to draw your attention to the principal conclusion 
which indicates that the first stage development of Aleltu, 
300 MW, is technically and economically very attractive at
the prefeasibility study level. The ultimate development, 
based on a staged development of 12 subbasins, would be in 
the order of 1,020 MW.
We strongly recommend that EELPA proceed with a feasibility 
study of the Aleltu project to substantiate technical and 
economic feasibility. There are several tasks which should 
be pursued at this time prior to and in preparation for the
recommended feasibility study; these are
-             install         additional         streamflow         and         rainfall         recording stations in the project area subbasins immediately
-    ensure that continuing recordings are being made at all of the meteorological and streamflow recording stations in and around the Aleltu project area
-   obtain 1:50 000-scale mapping of the entire project area.
ACRES INTERNATIONAL LIMITED
5259 Dorchester Road. PO. Box 1001, Niagara Falls. Canada L2E 6W1 Telephone 416-354-3831 Cables ACRESCAN Niagara Falls
Telex 061-5107 ACRES NFSEthiopian Electric Light
and Power Authority - 2
Details of these and other recommendations for ongoing work are contained in the report.
We take this opportunity to express our appreciation for the opportunity to work with EELPA staff as a project team in carrying out this challenging study.
Yours very truly
July 19, 1984
CJB:mam Encl
C. J-; Brown Executive Engineer
ACRES INTERNATIONAL LIMITEDACKNOWLEDGMENTS ACRES INTERNATIONAL LIMITED
wishes to express its appreciation to the Canadian International Development Agency and the Ethiopian Electric Light and Power Authority for their support in financing and for the many arrangements made in order to carry out this study. We also appreciated the significant contribution and the opportunity to work close with the staff of the Ethiopian Electric Light and Power Authority during this study. Thanks are also due to agencies of the Government of Ethiopia and others who contributed much of the basic information related to the Aleltu Hydroelectric Project.VOLUME 1 - EXECUTIVE SUMMARY
TABLE OF CONTENTS
GLOSSARY OF ABBREVIATIONS
LIST OF TABLES
LIST OF PLATES
PREFACE:
1  - CONCLUSIONS
2   - RECOMMENDATIONS
Page
1  -     INTRODUCTION -------------------------------------------------------------------------- 1
1.1     - General-------------------------------------------------------------------------------  1
1.2     - Terms of Reference and Scope of Work ------------------------------------  2
1.3     - Background--------------------------------------------------------------------------  2
1.4     - Study Execution--------------------------------------------------------------------- 3
2   -     RECONNAISSANCE STUDIES --------------------------------------------------------  5
2.1     - General-------------------------------------------------------------------------------  5
2.2     - Extent and Concept of Development--------------------------------------------- 5
2.2.1       -     Extent of Development-----------------------------------------------------  5
2.2.2       -     Development Concept ------------------------------------------------------ 6
2.3 - Reconnaissance Investigations and 
Project Layouts --------------------------------------------------------------- 8 2.3.1       -     Topographic Mapping, Aerial
Photographs and Surveys -----------------------------------------------  8
2.3.2       -     Hydrology and Reservoir Studies ----------------------------------------  8
2.3.3       -     Geological Assessment ----------------------------------------------------  9
2.3.4       -     Project Layouts--------------------------------------------------------------  9
2.4       - Project Evaluation ------------------------------------------------------------  9
2.4.1       - Description of Layout Optimization
Model---------------------------------------------------------------------  10
2.4.2       - Long-Term Grid Energy Supply Cost -----------------------------------  10
2.4.3       - Evaluation of Alternatives----------------------------------------------------  11
2.4.4       - First Stage and Ultimate Development
of the Aleltu Project-----------------------------------------------------  12
3   - PREFEASIBILITY STUDIES --------------------------------------------------------------  15
3.1     - General------------------------------------------------------------------------------  15
3.2     - Topographic Maps and Surveys-------------------------------------------------  15
3.3     - Hydrology and Reservoir Hydraulic
Studies------------------------------------------------------------------------- 15
3.4     - Geology and Geotechnical Investigations -------------------------------------  16Table of Contents - 2
Page
3.5 
- Socioeconomical and Environmental
Assessment---------------------------------------------------------------------  17
3.6        - Project Layout Alternatives -------------------------------------------------------  28
4   - DESCRIPTION OF RECOMMENDED FIRST STAGE
DEVELOPMENT OF THE ALELTU PROJECT -----------------------------------------  21
4.1            General ---------------------------------------------------------------------------  21
4.2        -  Basin Geology-------------------------------------------------------------------  21
4.3        -  Tiliku Development----------------------------------------------------------------  22
4.4        -  Interconnection Tunnel
and
Low-Level Outlet -------------------------------------------------------------  23
4.5        -  Jida Development------------------------------------------------------------------- 23
4.6        -  Dam Construction Materials------------------------------------------------------  24
4.7        -  Power Tunnel-----------------------------------------------------------------------  24
4.8        -  Penstock------------------------------------------------------------------------------  25
4.9        -   Powerhouse--------------------------------------------------------------------------  25
4.10      -   Switchyard and Transmission-----------------------------------------------------  26
5   - CONSTRUCTION PLANNING --------------------------------------------------------------  27
5.1         -   General -------------------------------------------------------------------------------  27
5.2         -  Construction Schedule--------------------------------------------------------------  27
6   - COST ESTIMATE-------------------------------------------------------------------------------- 29
7   - PROJECT POWER AND ENERGY CAPABILITY IN THE ICS — 
7.1        - Aleltu Project Generation Capability -------------------------------------------  31
7.2        - Timing of Plant Additions---------------------------------------------------------  33
31
8   - ECONOMIC ANALYSIS -----------------------------------------------------------------------  37
8.1        - Value of Capacity and Energy
for Stage I of the Aleltu Project -------------------------------------------  37
8.2        - Alternative Developments for Comparison —                                                   37
8.3        - Comparison Between Aleltu and
Gilgel Gibe--------------------------------------------------------------------  38
PLATESVOLUME 1 - EXECUTIVE SUMMARY
GLOSSARY OF ABBREVIATIONS
Acres                 Acres International Limited
ACSR                aluminum core, steel reinforced
ASTM               American Society for Testing and Materials B/C                   benefit/cost
CIDA                Canadian International Development Agency d                        day
DSL                  dead storage level
EELPA             Ethiopian Electric Light and Power Authority ENEL               Ente Nazionale Per L'Energia Elettrica ERESA             Eritrean Region Electrical Supply Agency FAO                 Food and Agriculture Organization
FI
flood index
FSCL                full surcharge condition level
FSL
ICS
full supply level interconnected system
MAF                mean annual flood Mm3                million cubic metres MM                  modified Mercalli MSL                 mean sea level
PF
PI
plant factor plasticity index
PMF                 probable maximum flood PPS                  Power Planning Study PTD                 power tunnel diameterGlossary of Abbreviations - 2 PVC                  polyvinyl chloride
r/min
revolutions per minute
scs               self-contained system
t
tonne
UNDP                United Nations Development Program USBR                United States Bureau of ReclamationVOLUME 1 - EXECUTIVE SUMMARY LIST OF TABLES
Number
Title
1
2
3
4
5
Basins and Drainage Areas
Power and Energy Capabilities f
Staged Ultimate Aleltu Development
Stage I -
Prefeasibility Cost Estimate
Aleltu Project Power and
Energy Capabilities
Aleltu Project -
System Supply CapabilityVOLUME 1 -
EXECUTIVE SUMMARY
LIST OF PLATES
Number             Title
1 Potential Development
of Aleltu Project
2
North-South Projection of
Gorge Profiles and
Powerhouse Locations
3
Reconnaissance Layout Arrangement
4
Ultimate Development of Aleltu Basin
5
Geological Section of
the Zega Wedem Gorge
6
Project Layout Plan
7
Tiliku Aleltu Dam and Spillway
8
Tiliku Aleltu and Jida Structures
9
Jida Dam and Spillway
10
Power Conveyance Structures
11
Powerhouse Arrangements
12
Construction SchedulePREFACE
The reconnaissance and prefeasibility studies described in this report have defined the ultimate development potential of the Aleltu project and the first stage of development. The results of the studies are presented in the following conclusions and recommendations.
1 - CONCLUSIONS
(a) Reconnaissance Study
1     - Based on an extensive reconnaissance study, an optimum concept of the ultimate project was estab lished. This concept is based on a staged develop
ment of subbasins with interconnected reservoirs and conveyance of power flow through one power conduit to a single powerhouse located in the lower reaches of the Zega Wedem Gorge.
2     - The theoretical potential of the Aleltu project
area for hydroelectric power generation is about 3,800 GW*h/yr. This potential is contained in
14 subbasins.
3     - The economic generation potential of the Aleltu project area is about 3,600 GW«h/yr and the installed capacity at 40% load factor would be about 1,020 MW. This economic potential would be derived from 12 subbasins, with two basins not being economical to develop.(ii)
4    - The most economic and practical first stage of
development      is      the      Tiliku      Aleltu      scheme,      followed by the- Ji da scheme.
5    - Future schemes for implementation are
-   Weserbi (plus possibly Girar and Gur)
-   Gomoro
-   Robi
-   Chacha
-   Duber
-   Robi-Gomoro
-   Jinjer
-   Sibilu.
(b) Prefeasibility Study
6     - Studies carried out at prefeasibility level of the Tiliku Aleltu and Jida subbasins showed that this first stage of development is technically and 
economically promising.
7     - The generation potential of the first stage development is 1,040 GW«h/yr of firm energy. An installed capacity of 300 MW was selected.
8     - There are no social or environmental factors which should prevent implementation of the Aleltu project.
9     - The construction cost, including transmission, substation, socioeconomic costs, contingencies, engineering and construction management, and owner's administration of Stage I of the Aleltu project is US $407 million.( iii)
10  - Based on construction costs
and substation costs at the
- the unit cost of capacity
- the unit cost of available firm energy is 47.1      mills/kW«h (at 12% discount rate).
(including transmission load center)
is US $l,357/kW
At investment cost level, this would correspond to
59.5          mills/kW*h.          This          cost          compares          favorably 
with       the       average       investment       cost       of       future       ICS energy supply of 67 mills/kW«h.
11   - The comparative economic costs between Aleltu and
Gilgel      Gibe      show      the      Aleltu      project      to      be      about      35% lower in unit cost than the Gilgel Gibe project.
2 - RECOMMENDATIONS
(a) Project Development
Recommendations
1 - As the first priority, in consideration of meeting future load demands of the ICS, it is recommended, with respect to the Aleltu project, to carry out a feasibility study of the first stage of development, i.e., the Tiliku Aleltu and Jida basin schemes.Allowing for normal financing, engineering ana construction periods, the feasibility study should 
be started at least 8 years in advance of the
required on-line date. If the studies were started before the end of 1984, the first units could be
on-line in January 1993.
2 - As the second priority, in consideration of planning 
for the ultimate development of the Aleltu project, 
it is recommended to carry out a prefeasibility study of the second stage of development, i.e., for development after the Jida basin scheme.
Technical Recommendations
The most significant technical recommendations are to
1 - supplement the present streamflow gauging stations
in the basin Oy installing new streamflow and 
rainfall recording stations in all subbasins
immediately
; - continue cata recording at all meteorological and 
st reamf .o*> recordnc stations in and around the
t.t.ii. pre ect tas.r.
. ,t 11.. •      ■ aa oot-sca-e mapping of the entire project
A)
. i
y
.nvefct
to conf 1 rm the reservoir1.1 -
Electric power Supply l*
Ethiopian Electric LI$M Aleltu project was ident Study (PPSI* as one of * for economic hydroelectr development
1 < * i ** 5 s      i •     eneir • ' • ii
S nd r* we ♦           i h* i I >            t • i r a If 1e‘ 1 * 1          He    i > 11 Pr we i t j a n* i
•* •
nusbet ef        F*      e r * ♦ W 1 ♦“            1 • * 1 e • a lc develop           -w • 1        THe mein t m                  e < i
about MO *r r- >t t •
’    <»•     ♦   •   • •
In the PPS, the Al«ltu project
sance Level. EELPA, aa part of ita overall
•’     *«•••>. at i
planning,        has        decided        to        idv«nc»        thia        pi        •        v-        jtafeaa. ity level to determine
- more accurately                    its tochnic.il and acon<>at aatli*
- if it should be considered (Ln competition *ith mhet
potential power projects) tor mooting the nation*!
increasing load demand
- if it should proceed to a full feasibility level atudy.
In early 1983, discussions were conducted, and on Juno 29, 1983, an agreement was reached between the Canadian International Development Agency (CIDA) and EELPA for joint financing of the reconnaissance and prefeasibility study ot the Aleltu project. Acres International Limited (Acres) was engaged to perform the study jointly with professional and technical staff of EELPA.
*Power Planning Study, Acres International Limited, October 1982.'(iv)
Allowing for normal financing, engineering and construction periods, the feasibility study should be started at least 8 years in advance of the required on-line date. If the studies were started before the end of 1984, the first units could be
on-line in January 1993.
2 - As the second priority, in consideration of planning for the ultimate development of the Aleltu project, it is recommended to carry out a prefeasibility study of the second stage of development, i.e., for development after the Jida basin scheme.
( b) Technical Recommendations
The most significant technical recommendations are to
1 - supplement the present streamflow gauging stations in the basin by installing new streamflow and rainfall recording stations in all subbasins immediately
2   - continue data recording at all meteorological and streamflow recording stations in and around the Aleltu project basin
3  - obtain 1:50 OOC-scale mapping of the entire project area
4   - carry out investigations to confirm the reservoir integrity at the Tliiku Aleltu and Jida sites.1 - INTRODUCTION
1.1  - General
Electric power supply in Ethiopia is administered by the Ethiopian Electric Light and Power Authority (EELPA). The Aleltu project was identified in the 1982 Power Planning Study (PPS)* as one of a number of projects with potential for economic hydroelectric development. The main project development is about 80 km north of Addis Ababa.
In the PPS, the Aleltu project was studied at prereconnais sance level. EELPA, as part of its overall generation 
planning, has decided to advance this project to prefeasibil
ity level to determine
- more accurately                 its technical and economic merits
- if it should be considered (in competition with other
potential power projects) for meeting the nation's
increasing load demand
- if it should proceed to a full feasibility level study.
In early 1983, discussions were conducted, and on June 29, 1983, an agreement was reached between the Canadian International Development Agency (CIDA) and EELPA for joint financing of the reconnaissance and prefeasibility study of the Aleltu project. Acres International Limited (Acres) was engaged to perform the study jointly with professional and technical staff of EELPA.
"Power Planning Study, Acres International Limited, Oct ober 1982 .2
1.2    - Terms of Reference
and Scope of Work
The Terms of Reference and General Scope of Work can be summarized as follows.
- Undertake an initial assessment of the Aleltu Basin at reconnaissance level to define the ultimate hydroelectric potential of this basin.
- Define, at prefeasibility level, the first stage of the development.
1.3   - Background
The Aleltu project connects with the main interconnected syltts (ICS).
The installed capacity of the Main ICS is presently 213.7 MW. 
Of this, 
xs provxdec oy four hydroelectric power plants,
namely, Kok a, Awash II, Awash III and Finchaa.
T < Amar*- civemor anc Malka Wakana projects are presently 
construct .or.. The ICS capability after completion of
<rfr,e project* ;r .987 wi.l be 348.5 MW of dependable
capacity and .,761 O-h/yr of firm energy.
< ow. ng economy and e . e* t r i f l c a 11 on pr og rains will dema nd i eaalng supply of power one energy. The 19H2 PPS shows 
<hat tui< will i/» a
tor oddi t lor>a generation,
.;<■             . Hg oi the »• ad fore^ aai afcb .jibe-l , be < ween . W9 and
, 99 j| .
r     ui     <     ha     ,     *96     a     and     into     (he     no     f     cent     uf     y,     t     Itc     up!     imou Z>e »/€ , <.<        n I pi I an C mJ I hr i't W * J L*« pl . Mia Illy hy Cl l> .3
Ethiopia has a large number of potential developments, mai.-.L) located in the Omo and Blue Nile basins. The most promising developments were found to be the Aleltu and Chemoga develop ments in the Blue Nile Basin and the Halele Werabesa develop ment in the Omo Basin. In the 1982 PPS, it was recommended to advance these projects to full feasibility status as early 
as possible. In comparing the three recommended develop ments, it was found that the Aleltu project appeared to be
the most attractive from a number of viewpoints
-    large generating head, about 1,100 m
-    potential generating capability up to 800 MW
-    development can be in stages
-    favorable location close to Addis Ababa and adjacent to the main road to Bahar Dar
-    low investment cost.
For practical consideration of project management, the size of new major generating plants should meet the ICS load growth for a period of at least 5 years. Considering load growth in the 1990s, this would correspond to an installed capacity of 180 MW or more. Aleltu satisfies this
condition.
1.4    - Study Execution
The study was executed in two phases—reconnaissance and prefeasibility—during the period from July 1983 to issue of the final report in June 1984. Field investigations were conducted in both phases of the study to develop site specific data for the multidisciplinary office studies and project designs.5
2 - RECONNAISSANCE STUDIES
2.1 - General
The objectives of the reconnaissance studies were to
- identify all possible development alternatives
- determine the concept of development and economic capability of the complete project
- define the optimum first stage of development.
2.2   Extent and Concept 
of Development
The Aleltu project is located on the high plateau area of Central Ethiopia. It is bounded approximately by Addis Ababa to the south, Fiche to the northwest and Debre Berhan to the east.
2.2.1 - Extent of Development
Fourteen subbasins with potential for power development were identified on the high plateau. Plate 1 shows the drainage basins and potential ultimate development of the Aleltu project. The rivers of the 14 subbasins presently discharge into four larger river basins. These are
- Zega Wedem, in the northcentral part of the project area
-   Bersina, northeast of the Zega Wedem
-   Giamma to the east
-   Muger to the west.6
These major basins, together with the subbasins and their drainage areas, are shown in Table 1.
All practical damsites (over 30) were identified as shown on Plate 1.
2.2.2 - Development Concept
The major features that create the Aleltu project are a combination of reservoirs (river valleys) located upstream from the Zega Wedem and Bersina gorges and the high head that can be developed in these gorges. The major part of this head is from the edge of the plateau to the bottom cf the gorge. Plate 2 shows sections along the Zega Wedem and Bersina gorges. In both gorges, the potential head increases to the west going away from most basin developments.
From a stuav cf the topographic maps, it was found that many of the valleys are close to one another and have approximately the same elevations. They are the Agat, Tinishu Aleltu, Tiliku Aleltu, Jida, Gomoro and Robi. It was therefore considered that the reservoirs in these basins could probably be interconnected with low cost uncontrcllec channels or tunnels and operated as an integrated network with a common reservoir level.
From; the interconnected reservoirs, a power tunnel (or canal) anc penstock could convey power flow to a common powerhouse located in tne Zega Wedem or Bersina gorges. Alternatively, more than one powerhouse could be considered; one in the Zega wedeii Gorge for development oi western basins and one in the Bersina Gorge for
eastern basins.7
TABLE 1
BASINS AND 
DRAINAGE AREAS
Major
Subbasin
Basin
No. *
River
Drainage
Area** 
(km2)
Zega Wedem         1
Gur
2          Weserbi
3          Agat
4          Tinishu Aleltu
5
Tiliku Aleltu
6
Jida
7
Robi-Gomoro
8
Gomoro
9
Robi
Bersina
10
Jinjer
Muger
11
Girar
12
□uber
13
Sibilu
Giamma             14 TOTAL
Chacha
93***
168
86
77
458 749 272+ 225 437 238 312
172 518
590
4 395
’ The subbasins are numoered crom west to east and north to south, starting with the Gur, which is the most nortnwesterly basin.
*" Drainage areas correspond co basin area ac main damsites on 
each river.
""’Excluding tne weserbi tributary.
r
Dramage area is downstream from Root and Comoro sites.8
Basins distant from the gorges and those not suitable 
for developing as part of the integrated network could 
be developed as diversion projects.
2.3 - Reconnaissance Investigations 
and Project Layouts
2.3.1 - Topographic Mapping, Aerial 
Photographs and Surveys
The entire project area is covered by 1:250 000-scale mapping with interpolated 50-m contour intervals.
Mapping at 1:50 000-scale with 20-m contour intervals 
is available over that part of the project area west of longitude 39°00’ (see Plate 1). This covers about one 
third of the project area. The 1:250 000-scale mapping 
is not adequate for reconnaissance or prefeasibility 
level studies, and therefore the available mapping was supplemented by extensive ground surveys carried out by EELPA.
2.3.2 - Hydrology and
Reservoir Stucies
Hydrologic stucies of basins in the Aleltu project area were undertaken to assess
- the available flows for hydroelectric generation
-           the       required       reservoir       volumes       'and       dam       heights)       at varying        degrees        of        flow        regulation        for        Separate        and integrated reservoir operation
-    the flood flows which will govern trie design of diversion works end spillways.a
2.3.3 - Geological Assessment
Regional and local geological conditions were assessed 
in the Aleltu project area for the purpose of designing structures (at reconnaissance level), preparing layouts and cost estimating.
Geological and geotechnical conditions were considered to be acceptable at locations considered for the major project structures—dams, power conduits and
powerhouse.
2.3.4 - Project Layouts
Conceptual designs and layouts of the alternative developments were prepared, as shown on Plate 3, for the comparative evaluation in the reconnaissance studies. The work included
- layout of project components within topographic constraints to suit the ultimate project development
- establishment of relationships between project layout and project operation requirements, i.e., dam volume/reservoir full supply level (FSL), reservoir volume/elevation, energy generation/reservoir FSL, etc.
2.4 - Project Evaluation
As mentioned in the previous sections, the Aleltu project is a complex development. The combination of its 14 basins, each with alternative schemes of development, including dam locations, reservoir sizes, interconnection tunnels or open channel conveyance structures, power tunnel, penstock routes10
and powerhouse locations, provides for a large number of development options.
A special approach was required to address these options. Initially, alternative development options for the basins and the powerhouse location were screened to identify the most promising schemes. The screening analysis was followed by extensive use of a layout optimization model.
2.4.1 - Description of Layout
Optimization Model
The layout optimization model, developed for the Aleltu project, incorporates a hydraulic network strategy with reservoir operation and economic analysis. This model evaluates any combination of schemes in the Aleltu project by considering five variable project components which have the major influence on project economics. These are
- cams
- interconnection tunnels
- power tunnels
- penstocks
- powerhouses.
2.4.2      - Long-Term Grid
Energy Supply Cost
The economic criterion used in the layout optimization mocel is that the incremental cost of available energy suppiiec by the Aleltu project schemes must be less than 35 mills. This cost excludes construction camp and facilities, contingencies, management, engineering, owner's cost and interest during construction.11
This parameter was derived from the 1982 PPS report. Therein, the future cost of available grid energy was calculated by considering the cost of energy production of alternative projects for the ICS.
2.4.3 - Evaluation of
Alternatives
A total of about 80 development alternatives were investigated with the layout optimization model. The study yielded a clear definition of the ultimate development concept of the Aleltu project.
- From a consideration of maximizing head (by develop ing the downstream powerhouse Site A in the Zega Wedem) and minimizing the length of the power con duits, the Agat followed by Tinishu Aleltu would be a promising development plan. However, unfortu nately, both the Agat and Tinishu Aleltu proved to be very expensive compared to the long-term value of grid energy.
- The Tiliku Aleltu, Jida, Gomoro and Robi schemes would be developed in an integrated manner; with the reservoirs interconnected for operation at a common reservoir level.
- The optimum location of the power tunnel intake is at the Tiliku Aleltu reservoir.
- All power flows would be turbined at powerhouse Site A.12
- There are three diversion schemes which the reconnaissance study has evaluated to be economic, namely, the Weserbi, Duber and Chacha.
- Four other basins—Gur, Girar, Jinjer and Sibilu— 
have been identified as diversion schemes but have 
not been evaluated. These schemes are expected to be developed at a later stage of the Aleltu project and 
do not affect the conclusions of the reconnaissance 
study.
2.4.4 - First Stage and Ultimate
Development of the Aleltu Project
From the study of alternatives, it was determined that the Tiliku Aleltu scheme would be developed first.
This results from the optimum powerhouse location being at Site A, near the confluence of the Zega Wedem and 
Agat rivers, where the maximum available head is about 
1,100 m.
Following Tiliku Aleltu would be the Jida as part of the first stage of construction.
The Tiliku Aleltu and Jida schemes would only be the first stage of the economic potential of the Aleltu project. The development of the ultimate project is expected to be as follows
- Stage IA - Tiliku Aleltu
- Stage IB - Jida13
future stages
(a)  Weserbi (plus possibly Girar and Gur)
(b)  Gomoro
(c)  Robi
(d)  Chacha
(e)  Duber
(f)  Robi-Gomoro
(g)  Jinjer
(h)  Sibilu.
The overall arrangement of the ultimate development is shown on Plate 4. The energy and capacity additions for this sequence of development, together with the average cost of project energy, are shown in Table 2. As the ICS load demand increases, the Aleltu project can increase energy production in stages with average energy costs generally decreasing.
The firm energy generated for the ultimate development is estimated to be 3,592 GW*h at an installed capa city of 1,023 MW (at 40% load factor). This capability would meet ICS load demands (for the standard load forecast including boilers, and implementation in the mid-1990s) for about 15 years.14
TABLE 2
POWER AND ENERGY CAPABILITIES OF STAGED ULTIMATE ALELTU DEVELOPMENT
Development
Firm    Energy (GW.h)
Add I tlons Accumulative
4  In 0 st  $  aP ll laednt CFaapctaocir ty  (MaWt )
Additions         Accumulative
Average    Cost    of Project Energy*
(ml 1Is/kW-h)
Stage 1A
240
- Tlllku Aleltu**
240
)
34.6
Stage IB
)
)286
286
763
- J Ida**
1 003
)
)
25.6
Future stages
- Weserbi***
168
1 171
- Gomoro
48
189
334
1 360
25.1
- Robl
51
317
385
25.0
1 677
- Chacha
90
458
475
- Duber
2 135
24.2
131
298
606
23.8
2 433
- Glrar***
85
172
2 605
691
740
767
24.2
- Gur***
49
-
93
2 698
27
- Robl-Gomoro
220
2 918
- Jlnjer
63
830
-
156
3 074
45
- Slbllu
875
518
3 592
148
1 023
-
Note that corresponding long-term grid energy supply cost Is 35 ml I ls/kW*h.
** Note that data for Tlllku Aleltu and Jida will change slightly In the prefeasI bl 11ty study.
***Glrar and Gur could be Incorporated In development of Weserbi.iJi»h i I! ■) I i'i (If I'll K JJ W '1 ii ----------------------
15
3 - PREFEASIBILITY STUDIES
3.1 - General
In the reconnaissance studies, the Tiliku Aleltu and Jida schemes were identified as the first stage development of the total Aleltu hydro potential. Prefeasibility studies, as described in this section, were performed for the first stage development with the objectives of
- defining the project, including planning for construction and preparation of a capital cost estimate
- determining technical and economical viability.
3.2 - Topographic Maps
and Surveys
Topographic surveys and mapping initiated in the reconnaissance studies were continued, concentrating on the first stage development.
3.3 — Hydrology and Reservoir
Hydraulic Studies
Hydrologic/hydraulic studies were carried out to establish size and operating requirements of the project structures. These comprised16
- runoff and rainfall data analyses
- determination of monthly inflow sequences
- calculation of reservoir evaporation effects
- determination of reservoir regulation requirements
- assessment of potential reservoir sedimentation
- flood flow analyses
- reservoir routing calculations.
Studies of particular significance to the operation of the project were as follows.
Inflow Sequences
Because of poor historic correlations between the rainfall and runoff records of gauging stations in and around the project area, inflow sequences were derived utilizing synthetic methods and were based on a probabilistic rainfall-runoff relationship. By this method, the 
long-term average flows for the Tiliku Aleltu and Jida basins are 5.6 and 8.2 m3/s, respectively.
Reservoir Sedimentation
It was qualitatively established that sediment transport in the rivers on the high plateau area is expected to be small.
3.4 - Geology and Geotechnical
Investigations
The geological and geotechnical investigation program at the prefeasibility level was carried out to17
- assess foundation conditions
- locate natural construction materials
- determine design requirements relating to materials and seismic conditions.
Geological mapping was carried out for the damsites and the gorge. To determine the nature, depth and extent of over burden, 14 test pits and/or auger holes were excavated at the damsites:   5 at Tiliku Aleltu, 6 at Jida and 3 at Tinishu Aleltu. A geological section of the gorge along the power tunnel and penstock alignment is shown on Plate 5. Fourteen major rock units were identified. A summary of their description is included on Plate 5.
3.5 - Socioeconomical and
Environmental Assessment
Construction of the Aleltu project will have various social and environmental impacts on the surrounding community. To address these aspects of the project, a socioeconomic and environmental study of the Aleltu project area was carried out to
- identify the major social and environmental issues related to the Aleltu project
- assess the impact of the project on the local population and environment
- consider mitigating measures for the negative impacts.
Impacts on local inhabitants, farms, towns and villages, historical religious centers (particularly Debre Libanos), health and wildlife were evaluated.18
The significant impact arises from creation of the 
reservoirs.
With the extensive agriculture in the area, considerable 
farmland will be inundated by the reservoirs. The areas of 
the Tiliku Aleltu and Jida reservoirs are 7 and 52 km2, respectively. Most of the people in the area are peasant 
farmers at close to subsistence living. About 500 to 600 
families will be affected. However, the housing settlement 
pattern of the farmers on the plateau is important. The 
homes are generally in clusters, located on high land along 
the ridges of the valleys and not down in the valleys in the reservoir areas. Thus, very few homes will actually be 
flooded.
•—* Several rehabilitation programs have been considered
- a redistribution of farmlands and compensation by support
programs
- a fertilizer program for existing lands and an equipment
support program
- a resettlement program.
3.6 - Project Layout Alternatives
The general arrangement of the first stage of the project was established in the reconnaissance studies.
In the prefeasibility stage, layout studies were conducted to produce a functional project in accordance with good hydro electric engineering practice. Significant considerations in the project layout were19
- the sites for the main dams
- low-level outlet requirements for drawdown of the
reservoir
- unregulated spillways
- power tunnel routing
- a single large-diameter tunnel to provide for Stage I
plus future flows of Gomoro-Robi and Chacha basins, or separate tunnels
- surge chamber size
- penstock routing
- powerhouse location with respect to suitable foundation conditions.
The results of these studies are presented in the following Section 4, Description of Recommended First Stage Development of the Aleltu Project.21
4 - DESCRIPTION OF RECOMMENDED FIRST STAGE DEVELOPMENT OF THE ALELTU PROJECT 
4.1 - General
The first stage development of the Aleltu project would consist of
- development of the Tiliku Aleltu and Jida river basins
-  installation of 300-MW capacity with firm energy generation of 1,040 GW-h.
General features of the project layout are shown on Plate 6 and summarized below.
The first stage has been developed in such a way that future extensions can be easily incorporated. This includes connec tion of future reservoirs to the first stage reservoirs, doubling of the power conduits and extension of the power house .
4.2 - Basin Geology
Overburden in the reservoir area is estimated to be very thin. The bedrock consists of different flows of basalt—at least two flow units of basalt and the associated weathered contact zones are recognizable near the damsites at eleva tions within the reservoir. Groundwater seepage and springs have been observed in the valley slopes on the alignment of these contact zones. This seems to suggest that the contact zone is water bearing and permeable.22
The geological weaknesses resulting from the weathered contact zones may comprise potential seepage paths and, if extensive, these would require treatment to curtail leakage. To cope with any potential seepage paths, provision has been made in the layout design and cost estimate
- to seal these areas (with an impervious blanket, grout or other method) during the construction period
- if required, to draw the reservoir down through a low-level outlet to treat any problems.
4.3 - Tiliku Development
The reservoir at Tiliku Aleltu is about 9 km long, varying in width from about 400 m wide at the narrowest section (dam location) to 4 km wide at the widest section, and a total reservoir volume of 92 Mm3, at an FSL of 2,598.5 m. Live storage at FSL is 90 Mm3. This live storage volume is the maximum available, being limited by topography, and will only provide for about 60% regulation of the natural inflows.
An earth- and rock-fill dam is provided at the Tiliku Aleltu site. The maximum height of the dam is 54 m above the lowest point of the bedrock foundation. Typical sections of the dam are shown on Plate 7.
With the basalt bedrock, foundation conditions are adequate for construction of an earth- and rock-fill dam.23
4.4 - Interconnection Tunnel
and Low-Level Outlet
The Tiliku Aleltu and Jida reservoirs are interconnected by a 2 km tunnel, and both reservoirs operate the same level. A low-level tunnel is provided for emergency drawdown of the two reservoirs to inspect the dams or to expose the basalt contact zones in the lower elevations of the reservoir, if necessary. The low level tunnel is taken off the interconnection tunnel between the two reservoirs, as shown on Plate 6 and Plate 8.
4.5 - Jida Development
The Jida reservoir is considerably larger than that of Tiliku Aleltu. It will be approximately 27 km long and 4 km wide at its broadest point. The Jida reservoir will provide about 90% of the total live storage for the Stage I development. The other 10% will be provided by Tiliku Aleltu. Full flow regulation for both the Tiliku Aleltu and Jida rivers inflow will be achieved at FSL of 2,598.5 m corresponding to a live storage of 990 Mm3,
Similar to the Tiliku Aleltu scheme, an earth- and rock-fill dam is provided at Jida. Crest elevations are the same for both dams, but maximum height of the Jida dam is 65 m above the lowest point of the bedrock foundation which is 11 m higher than Tiliku Aleltu.
Typical sections of the main dam and cofferdam in the riverbed are shown on plate 9.24
4.6 - Dam Construction Materials
The dams at Tiliku Aleltu and Jida have been designed to maximize the use of local materials. The volumes of materials required for the two dams are as follows.
Tiliku
Material
Zone
Aleltu 
(Mm3)
Jida
(Mm3)
Compacted impervious
1
0.15
0.90
Compacted filter
3
0.07
0.40
Compacted transition
5
0.18
0.88
Compacted rock fill
7
0.56
4.79
Riprap
9
0.04
0.15
TOTAL
1.00
7.12
In general, with the exception of transition material, 
adequate supply of materials is available from natural 
sources within economic hauling distance of the damsite.
The source for the transition material will be crushed basalt as there is no other natural source (such as gravel beds) for this gradation of material.
4.7 - Power Tunnel
The power tunnel alignment is shown on Plate 10. It is expected that the rock quality in the upper basalt and in the lower agglomerate will be of good quality, except in local areas where the tunnel crosses any flow contacts or discon tinuities. The basalt, however, could have extensive fractures and/or be heavily fissured. This would present no significant structural or construction problems but may25
provide leakage paths for the power flow. Therefore, for support of weak zones and to ensure containment of the power flow, a permanent concrete lining of 21.5-cm (one-fifteenth of the diameter) thickness has been provided for the entire length of the tunnel and the concrete/rock interface will be contact grouted.
Rock quality in the upper lacustrine unit is poor and, for the shaft through this zone, steel support and/or reinforced 
shotcrete will be required to stabilize the
4.8 - Penstock
The surface penstock will be constructed of steel extending from the termination of the
power tunnel, in-
the agglomerate zone, to a manifold at the powerhouse. The manifold will connect to the six turbine/generator units of the Stage I development.
4.9 - Powerhouse
The surface powerhouse will be located on the east bank of the Agat River, approximatley 500 m from the confluence with the Zega Wedem River and approximately 18 km from the Tiliku Aleltu power intake. A general arrangement of the powerhouse is shown on Plate 11. The powerhouse is located in such a way that future extension can easily be accommodated co che northeast. This will also suit the construction of a future secondary penstock along the northeastern side of the proposed penstock.
The access road to the powerhouse winds over 14 km down the race ot the gorge, as shown on Plate 6.26
4.10 - Switchyard and
Transmission
The switchyard will be located on a terrace above and upstream from the powerhouse, with orientation convenient for connections from the powerhouse and the outgoing lines.
From the Aleltu switchyard, a 230-kV, double-circuit trans mission line comes off the dead-end towers and is routed up the gorge alongside the penstock. From the top of the gorge, the line runs due south cross-country over the plateau to Highway 3 south of Debre Tsige. From this point, the line generally follows the highway to Addis Ababa.27
5 - CONSTRUCTION PLANNING
5.1 - General
Several of the structures will require specialized con tractors, such as for the long power tunnel, steel penstock and the access road. However, these same structures are conventional in design and similar in size to other hydroelectric projects in Ethiopia and internationally.
It has been assumed that one main civil construction contract would be awarded to an international contractor selected by competitive tendering. Separate civil contracts for access roads and construction camps are considered to facilitate an early start. Major mechanical and electrical equipment and the transmission lines would be contracted by competitive tendering from international manufacturers.
5.2 - Construction Schedule
An engineering and construction schedule for the Aleltu hydroelectric project is shown on Plate 12.
Stage I construction of the Aleltu development has 300-MW installed capacity. This construction is carried out in two periods. Stage IA is the Tiliku Aleltu development with three 50-MW units installed. Stage IB is the Jida develop ment for which an additional three 50-MW units would be installed.
The time from project commitment to first unit on-line for construction Stage IA is 5.25 years. Units 2 and 3 come on-line at 1.5-mo intervals thereafter. For Jida, the28
construction schedule depends on the ICS requirements.* For the standard load forecast, including boilers and assuming no ICS regulation for the Tiliku Aleltu flows, Unit 4 (which is part of Stage IB) comes on-line 1.5 years after the first unit. Units 5 and 6 follow at 1.5-mo intervals. If other reservoirs in the ICS can provide regulation for Tiliku Aleltu flows, then Stage IB could be delayed with Unit 4 coming on-line about 2.75 years after Unit 1.
*The ICS requirements are discussed 
c , ,
1  SeCtl°n
Project Power and Energy Capability in theses " 29
X 6 - COST ESTIMATE
The total estimated construction cost* of the Aleltu hydro project is US $406,700,000 at January 1984 price levels.
This cost represents total project costs, including construc
tion power transmission and switching, socioeconomic cost, engineering construction management and owner's cost.
A summary of the Aleltu prefeasibility cost estimate is shown in Table 3.
Contingencies
Contingencies for unforeseen work, or conditions which may cause a premium on unit costs, have been added to each subaccount. Overall, the contingency is 20.7%.
Taxes and Duties
Ethiopian taxes and duties on imported equipment and materials, and any Ethiopian taxes on contractors' and consultant's revenues and salaries have not been included.
Interest During Construction
Interest during US  $106,960,000 investment cost
construction, at 12%/yr, amounts to 
(26.3% of the construction cost). The (in 1984 dollars) becomes US $513,660,000.
, *Construction cost is total cost to construct the project, including contingencies but excluding interest during con struction and escalation. Investment cost = construction cost + interest during construction but excluding
escalation. 
yTABLE 3
STAGE I -
PREFEASIBILITY COST ESTIMATE (6x50-MW Units)
Item 
00 
Description
Infrastructure
01 
Reservoir
02 
Interconnection tunnel (including low-level outlet)
January 1984 US Dollars*
58,940 ,000
2,100 ,000
12,750,000
03       Dams (Tiliku Aleltu and Jida)
04       Spillways (Tiliku Aleltu and Jida)
05       Power intake
06       Power tunnel (including surge and valve chambers)
07       Surface penstock
08       Powerhouse (including electro mechanical equipment)
09      Switchyard
10      Socioeconomic
11       Transmission
12       Gafarsa substation
Subtotal
Engineering and construction management Owner's administration
TOTAL CONSTRUCTION COST
99,960,000
4,780 ,000
2,690 ,000
59,510,000
22,880,000
57,800,000
9,600 ,000
8,000 ,000
10,920 ,000
13,200 ,000
363,130 ,000
36,310 ,000
7,260 ,000
406,700 ,000
‘Each cost item includes its respective contingency.31
7 - PROJECT POWER AND ENERGY 
CAPABILITY IN THE ICS
7.1 - Aleltu Project
Generation Capability
From a review of the ICS requirements, it is considered that the Aleltu project, if installed in the mid-1990s or soon thereafter, should have a plant factor of about 40%.
The power and energy capability of the first stage of development is shown in Table 4.
As reported in previous sections, the Tiliku Aleltu reservoir is too small to provide for full flow regulation. Thus, as shown in Table 5, Tiliku Aleltu, by itself, provides
- 260 GW-h/yr firm energy
- 180 GW-h/yr secondary energy.
This secondary energy could contribute to the ICS firm capability if it can be firmed up by the ICS existing reser voirs, or by the Jida reservoir.
The regulating capability of the existing ICS reservoirs was investigated during the 1982 PPS. It was found that after raising the Finchaa reservoir FSL, an additional regulating potential of about 295 GW«h/yr is available to firm up secondary energy generated by new plants. About 80 GW-h/yr of this potential will be needed for Malka Wakana. The remaining regulating capability of the ICS reservoirs is therefore in excess of 200 GW*h/yr. This potential could 
be used to firm up secondary energy generated by the Tiliku32
TABLE 4
ALELTU PROJECT POWER and energy capabilities
Tiliku Aleltu
As An 
Isolated With
Tiliku             Aleltu 
Description
Unit
Plant
Regulation*
Jida**
and Jida
Annual firm
GW*h/yr
260
440
620
1 040
energy 
production
Installed 
capacity
Secondary 
energy 
MW
150
150
150
300
GW-h/yr
180
10
10
20
capability
* 180 GW-h/yr of secondary energy firmed up by existing ICS reservoirs or by Jida reservoir.
**Performance of Jida is the same operating as an isolated plant or with ICS regulation, because of the large storage available at Jida.33
Aleltu scheme (or Gilgel Gibe project). If this ICS regulat
ing capability is available at the time of implementation of the Aleltu project, then the Jida scheme could be delayed to come on-line much later than Tiliku Aleltu. (This is 
discussed more fully in the next section.)
It is noted that the additional ICS regulation potential was 
not taken into account in sizing of the first stage develop ment of the Aleltu project in this study.* However, it is discussed here to indicate the influence of the ICS on the ultimate development of the Aleltu project.
7.2 - Timing of Plant 
Additions 
Depending on load growth, the Tiliku Aleltu and Jida schemes would first come on-line in the mid-1990s. Table 5 shows the capabilities of these schemes to satisfy load demands.
Depending on the load demand scenario
- Tiliku Aleltu, by itself without Jida, can meet the energy demands of the ICS for, at most, 3.5 years. In terms of a project to satisfy system demand for 5 years or more,
Tiliku Aleltu by itself is not sufficient. With Jida, the project will meet any expected load for more than 6 years, and the two schemes combined are therefore appropriate to consider as the first stage of development.
*It is considered that the regulation capability of the ICS should not be taken into account at this prefeasibility Level, of study since generation plans and the character of the ICS may change before implementation of Aleltu is 
rea1i zed.34
TABLE 5
ALELTU PROJECT -
SYSTEM SUPPLY CAPABILITY
Ability to Satisfy Load Demand (in years) TilIku Aleltu Without
TlIiku Aleltu with
Forecast Scenario
Standard forecast Including boIlers
Low forecast including bo Ilers
Standard          forecast oxcludIng bo Ilers
ICS Regulation___________ Capacity Energy
ICS Regulation
Capacity
Energy
TiIiku Aleltu
Plus Jlda____________ Capacity Energy
3-3/4
5-1/4                2 4-3/4
1-1/2                                                                7                      6
3-3/4
2-3/4
5-1/4
3-1/4
2-1/4
4-3/4
3-1/2
9-1/2 8
7-1/4
7-3/435
if the ICS cannot firm up the secondary energy of Tiliku Aleltu, the schedule for Jida, Stage IB, relative to commissioning of the units, should follow Tiliku Aleltu by 1.5 to 2.25 years. (The construction schedule, Plate 12, has been prepared on the basis of Jida, Stage IB, following Tiliku Aleltu, Stage IA, by the minimum of 1.5 years.)
if the ICS will firm up the secondary energy of Tiliku Aleltu, this scheme (Tiliku Aleltu alone) would meet ICS demands for an additional 1.25 years and Jida could be deferred for this same period. That is, Jida would follow Tiliku Aleltu by 2.75 to 3.5 years.37
8 - ECONOMIC ANALYSIS
8.1 - Value of Capacity and Energy
for Stage I of the Aleltu Project
Based on construction costs (including transmission and substation costs at the load center)
- the unit cost of capacity is US $l,357/kW
- the unit cost of available firm energy is
US $47.1 mills/kW-h (at 12% discount rate).
8.2 - Alternative Developments
for Comparison
Alternative projects to Aleltu were identified in the 1982 PPS. These included Gibe Daka (now Gilgel Gibe), Halele Werabesa, Chemoga Yeda and others. With the exception of Gilgel Gibe, these projects have only been studied at the prereconnaissance level and are therefore not adequately defined projects for comparison with Aleltu. Gilgel Gibe on the other hand has been recently studied at feasibility level and, although it has been committed for construction at this date, it is considered an appropriate project for comparison with Aleltu since
- both Aleltu and Gilgel Gibe are of comparable size
- both project studies are current
- both projects are for implementation in the ICS.
The power characteristics of Gilgel Gibe and Aleltu are as follows.38
Dependable capacity Plant factor Minimum net head Firm energy Average energy
8.3   Comparison Aleltu and
Unit
MW
m
GW* h/yr GW* h/yr
Aleltu Stage I 300
40
1 009 
1 040
1 060
Gilgel Gibe 285
25 230 670
820
Between Gilgel Gibe
There are various differences in approach to the development and the cost estimates of the two projects. To arrive at a meaningful comparison, the plant factor, scope of work and the cost estimates of the two projects were brought to a common base.
The following table contains the comparison of unit construction costs of capacity and energy.
Aleltu
Power Station
Aleltu
Gilgel
Gibe (adjusted)
Lower than Gilqel Gibe
(%)
Plant factor (%)
40
40
-
Installed capacity (MW)
300
181*
-
Firm energy (GW*h/yr)
1 040
670*
-
Total construction 
cost (US$ million)
407
377
Unit construction cost 
- US$/kW (installed)
1,357
2,083
65
- USS mills/kW-h
47.1
71.6
66
(available firm)
★Based on adjusting head used calculate dependable capacity
in Gilgel Gibe study
to
and firm energy,39
As indicated in the table, the first stage of the Aleltu project will be about 35% lower in unit costs than the proposed Gilgel Gibe development. It was therefore concluded that, based on this comparison, the Aleltu project appears to be highly economic and warrants further detailed studies.
I
I
I
I
I
I
r
iBAHAR 
GUR 
ZEGA                WEDEM 
DIVERSION  TUNNEL 
POWERHOUSE 
TO PENSTOCK POWERHOUSE 
DEBRE LIBANOS 
GUR 
DAM 
e-PENSTOCK 
SURGE CHAMBFR 
12c 
2640 
2660. 
2600 
JLA 
2560 
2580 
y2620 
2640 
-PUMPING -OPEN CHANNEI (SCHEME 
2a-1) 
-2620 
2b-1 12b-2 
2600 
STEEL SURFACE CONDUIT 
2600 
2c-2 
TILINU         DUSER 
(12c3 (12c-4 
Ta TILIKU 
ALELTU 
r2620 
2a 
WESERBJ DÁM 
i2c-5 
CONTROL WEIRS 
2640 
24-4 
TERE 
-TUNNEL 
2620          A2d-tNSHU       2644 
DEBRE 
TSIGE 
2640 
680 
AREA   A 
KILOMETRES 
AREA  B 
2 KILOMETRES 
No.  SUBBASIN 
GUR 
LEGEND 
2 
WESERBI 
3 
AGAT 
RESERVOIRS  AND  RIVERS POTENTIAL  DAMSITE 
4 
TINISHU  ALELTU 
TILIKU  ALELTU 
JIDA 
IDENTIFIED   DAMSITE POWERHOUSE   LOCATION 
7       ROBI-GOMORO GOMORO 
RO1 JINJER GIRAR 
2       DUBER SIBILU 
|4      CHACHA 
POWER  CONDUIT PROJECT  AREA SUB8ASINS 
ETHIOPIAN   ELECTRIC  LIGHT  AND   POWER AUTHORITY ALELTU   HYDROELECTRIC  PROJECT 
POTENTIAL  DEVELOPMENT  OF  ALELTU  PROJECT 
PLATE  I PROJECT 
ALELTU     DEVELOPMENT        OF 
POTENTIAL 
AUTHORTY 
PROUECT           HYDROELECTRIC 
POWER 
ALELTU 
AND 
LIGHT ELECTRIC 
ETHIOPIAN 
FLATE 
SUBBASNS 
AREA 
PROJEC T 
cONDUIT LOCATION    POWERHOUSE 
DAMSITE IDENTIFIED 
POWER 
-GOMORO ALELTU 
CHACHA SIBILU 
DUBER GIRAR 
JINJER 
ROBI 
GOMORO 
ROBI |DA 
ALELTU 
TILIKU TINISHU 
DAMSITE     POTENTIAL 
RIVERS 
RESERVOIRS                 AND 
AGAT 
WESERBI 
14 
13 
12 
I0 
9 
8 
7 
5 
3 
2 
TRES    KILOME 
20 
PLAN 
LEGEND 
SUBBASIN 
GUR 
No. 
9*00' 
ABABA ADDIS 
SENDAFA 
KILOMETRES 
KILOMETRES 
rSULULTA 
AREA     B 
AREA    A 
9°5 
'SHENO 
AREA B 
rCHANCHO          / 
Mt    SCHE   PUMPING 
CHANNEL 
OPEN 
DEBRE    TSIGE 
2640 
640 
M2d-I/ 
TUNNEL 
12 
2 
oCHACHA 
AREA A 
(D¤M WESERBI/ 
OMUKE 
TUR 
l2c-4 
r2620 
2600 
CONDUIT  STEE 
620 
CHANNEL -PUMPING 
SCHEME POMPINC 
FTAL 
0 
BRE 
2520 
BERHAN 
DEBRE 
MEND 
I2b-2 
12b-1                                                                                                                                                                                                                                                           580 
DESSIE 
TO 
CHAMBER 
SURGE                          MEDEM 
2560 
2600 
9°45" 
GAM 
ROBLIDA 
TUNNEL  OlVERSION 
POWERHOUSE 
OSRHOUSE 
zEGA 
LIBANOS 
PENSTOCK 
DEBRE 
DAR                  BAHAR 
TO 
RIVER 
OPEN 
INEWARE 
IEMA 
°00' 
3930' 
3915 
S900 
B8*45 GORGE 
PROJECTION 
OF 
NORTH-SOUTH 
LOCATIONS 
POWERHOUSE 
PROFILES 
AND 
AUTHORITY 
R\ET     HYDROELECTRC 
POWER 
ALELTU 
AND 
LIGHT ELECTRIC 
ETHIOPIAN 
NORTH 
VIEWING 
GORGES 
PROFILE       OF 
25 
KILOMETRES 
30 
DISTANCE  IN 
15 
1000 
20 
5 
I000 L 
GORGES 
BERSINA 
1200 
CONFLUENCE        OF 
AND 
JEMA 
GORGE 
MA JE 
|400 
l600 ELEVATION   ( 
GORGE 
MA JE 
LOCATION        G* 
I500.0 
EL. 
EL.1480.0 LOCATION A 
1440.0 
EL. 
GORGE 
BERSINA 
LOCATION           EL.I620.0      C 
EL.I590.0 LOCATION B 
LOCATION       A* 
|400 
LOCATION    I650.0       G 
EL. 
GORGE 
WEDEM 
ZEGA 
LOCATION    E 
I680.0 
EL. 
EL. 
I7200 LOCATION F 
EL. 
800 
I800.0 LOCATION H 
EL.I680.0 LOCATION D 
1600 
ELEVATION (m) 
300 
2000 
PLAN 
TRES   KILOME KEY 
ALELTU 
SHEMEN 
2000 
2200 
AGAT 
GUR 
WEDEM   ZEGA 
JDA 
2200 
2400 
DENEBA Q 
WEN 
ROB 
AHAR 
GORGE 
2400 
2600 
GORGE        ERSNA 
-PLATEAU 
INEWARE 
Ð 
2600 
WEMA 
45 S8 
N ARRANGEMENTS 
RECONNAISSANCE                              LAYOUT 
OSTANCE         (m) 
20     |500 
500 
DISTANCE                (m) 
AUTHORITY 
PRONECT      DROELECTRIC 
ALELTU        HY 
AND 
LIGHT  ELECTRIC 
ETHIOPIAN 
00 
PLATE 3 
POWER 
DISTANCE() 
) 
'580 
cb00  VATION  ELE 
DISTANCE            (m)                                                                                                                                     500 
2600 
2620 
2640 
S 
E 
PROFILES 
TOPOGRAPHIC             MAP 
SURVEYED 
26 
DISTANCE            (m) 1500                   1000 
2700 
2720 
ELEVATION (m) 
FROM PROFILES 
u2620 
I0b 
SITE 
ELEV 
LEGEND 
TOa 
SITE 
2000 
DISTANCE          (m) 
1500  I000 
2740 
2750 
2640 
660 
Z 
00 
tLEVAON  In 
2 
I2  SITE 
TUNNEL DIVERSION 
2620 
2640 
E 
CHANNEL 
SPILLWAY 
71LIK 
TUNNEL DIVERSION 
CHANNEL 
+SPILLWAY 
IOb 
SITE 
TOa 
SITE 
-2640 
TERCONNECTION 
GOMOR 
TUNNEL  TO 
14a 
SITE 
UINJER 
-2600 
2a   SITE 
CHANNEL 
SPILLWAY 
DIVERSION  TUNNEL 
(DUBER 
LIKU 
TIL 
SAMANYA 
INJER       EROMJIN. DIVERSION 
(ALTERNATIVE) 
CHACHA 
I2b 
SITE 
CHANNEL 
SPILLWAY 
BERSINA 
GORGE 
TUNNEL POWER 
TO 
JINJER 
9o  SITE 
TUNNEL 
DISTANCE          (m) 
DISTANCE          (m) 
1500 
I000 
DUBER 
DISTANCE  (m) 
2000 
500 
2520 
2540 
ELEVATION  (m) 
2580 2600 2620 
2000 
1500 
I000 
500 
WESERBI DISTANCE         (m    ) 
PEEREAM ROBI 
(m) DISTANCE 
I000 
500 
2540 
2560 
2540 
2560 ELEVATION            2580          (m) 
2600 
2620 
T500 
1000 
500 
0 
2000 
500 
500 
ELEVATION (m 
2580 2600 cb20 
ELEVATION (m) 
2520 2540 
2560 
25001 2520 
2540 
E 
INTAL 
40   SITE 
2580 
2560 VATION  ELE (r 
4b   sITE       FINAL                            2600 
2580 
E 
INTERCONNECTION 
10 26 
ALELTU TILIKU 
O 
4D  SITE 
ANTERCONNECTION    TUNNEL 
JIDA 
TO 
INTERCONNECTION TUNNELTO 
ALELTU 
JIDA 
INTERCONNECTION 
TILIKU TUNNEL          TO 
INTERCONNECTION 
ALELTU 
INISHU 
UNNEL       10 
CHANNEL         SPILLWAY 
40  sITE 
INTERCONNECTION 
ROBI 
TUNNEL 
8a  SITE 
CHANNEL 
SPILLWAY 
SITE      6c 
ALELTU                                                                  TIKKU 
sITE       5b 
TO 
2600 
TUNNEL 
POWE 
-2580 
CHANNEL SPILLWAY 
r 
sITE       30 
INTERCONNECTION 
AGAT 
TUNNEL 
TO 
CHANNEL 
SPILLWAY 
TUNNEL POWER 
T 
UNNEL 
POWER 
CHANNEL SPILLWAY 
ROAD 
GOMORO 
JIDA 
ALELn 
TILIKU 
ALELTU 
TINISHU 
AGAT BASIN ALELTU     DEVELOPMENT        OF 
ULTIMATE 
PROUECT          HYDROELECTRIC 
AUTHORITY 
POWER 
ALELTU 
AND 
LIGHT    ELECTRIC 
ETHIOPIAN 
FLATE 4 
SUBBASINS 
AREA PROJECT 
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CONVE 
FLOW 
POWERHOUSE 
RIVERS 
RESERVOIRS               AND 
TRES 
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DAR BAHAR HAR 
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1000' 
39°30' 
00' 
39° 
S8*45' 
N GORGE 
WEDEM 
ZEGA ALELTU 
THE 
SECTION        OF GEOLOGICAL 
PROJECT     HYDROELETRIC 
PLATE 5 
AUTHORITY 
POWER 
AND 
LIGHT ELECTRIC 
ETHIOPIAN 
RIVERS 
AGAT 
AND           WEDEM 
ZEGA CONFLUENCE        OF 
FROM DISTANCE 
500 
I000 
1500 
2000 
2500 
3000 
IVER 
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POWERHOUSE 
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PROFILE 
TEL. 
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PROFILE 
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w 
JOINTED   COLUMNAR 
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WITH    STRONG 
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EL EL 
EL 
1500 I600 
1700F 1800 
1900 
2000 
2100 
2200 
2300 
2400 (12)                 2500 
2600 
LITHIFIED 
UNITS BETWEEN 
FULLY 
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CON 
AND 
SALE 
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MEON 
BEDS 
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O 
WITH 
MOORATLLY                      TO    WEAK 
ONITS, 
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MISSVE  T 
LEGEND PLAN  LAYOUT 
PROJECT  HYDROELECTRIC 
PROJECT 
AUTHORITY 
POWER 
ALELTU 
AND 
LIGHT ELECTRIC     ETHIOPIAN 
PLATE6 
TRE   KILOME 
SELE 
25985 
EL  FSL 
ALELTU 
TINISMU 
INTERCONNECTION 
TUNNEL 
SPILLWAY EMERGENCY 
Lz600 
TSIGE 
DEBRE 
DAM 
JIDA 
LEVEL SPILLWAY 
OUTLET 
LOW 
600 
TILIKUALELTU              DAM 
2600 -
00. 
ALELTU 
TUNNEL 
POWER 
ALrU    TNSM 
230 
TRANSMSSION LINES. 
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MAHS 
CHAMBER 
SURGE CHAMBER 
PENSTOCK 
ACCESS 
ROAD 
WEDEM 
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DEBOs 
LIBANQS 
POWERHOUSE 
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bon 
ACCESS 
ROAD SPILLWAY 
AND 
DAM ALELTU 
TILIKU 
AUTHORITY 
PROUECT DROELECTRIC 
ALELTU        HY 
ANO 
LIGHT ELECTRIC    ETHIOPIAN 
PLATE 7 
POWER 
SECTION 
TYPICAL    SPILLWAY 
ALELTU 
TILIKU 
PROFILE 
SPILLWAY 
ALELTU 
TILIKU 
TRE 
ME 
TRES 
ME 
600 
500 
100 
50 
l2590 
640 
400 
300 
200 
100 
ELEVATION  (m) 
2610 
4 
25960 
-EL 
2610 
2630     3 
q2650 E 
LEVEL      GROUND 
CREST 
WAY 
SPILL 
2630 
6 
VARIES 
CHANNEL  DISCHARGE 
Ç 
VARIES 
UPSTREAM) 
(LOOKING 
LINE     CENTRE 
DAM           ALONG 
SECTION 
TP-TAD-5. 
LOCATION     OF 
TP-TAD-l        TO 
FOR 
3.2 PLATE 
PITS 
TEST 
SEE 
NOTE: 
TRES 
ME 
BEDROCK FRACTURED 
BASALT) 
2570 
2590 
2610 
BEDROCK 
SOUND 
WEATHERED         OR 
CORE 
FOR          LEVEL       FOUNDATION 
ELEVATION  (m) 
TP-TAD-3          (PROJECTED) 
2550L 
2570} 
TP-TAD-I           PHOUECTEDL 
2601.0 -
EL. CREST 
DAM 
TP-TAD-2             (PROJECTED) OVERBURDEN -
2602.0 
EL. CREST 
DAM 
(PROJECTED)                 -TAD-4 
SHEL LEVEL         FOUNDATION 
TP-TAD-5 
(PROJECTED ) 
FOR 
2601.0 
EL. CREST 
-DAM 
ELEVATION  (m) 
690F 2610 
BED    RIVER 
SECTION       IN  MAXIMUM 
METRES 
ROCKFILL                  ZONE 
RIPRAP 
BASALT COMPACTED 
20 
ZONE DRAINAGE   cOMPACTED 
LINE      GROUT 
TRANSITION                   ZONE 
cOMPACTED 
(9) 
(5) 
(3) 
J2540 
2550 
2560   w 2670 
2580 E 2590 
12600 
FRACTURED 
(BASALT)   WEATHERED        OR 
BEDROCK 
(BASALT) 
BEDROCK 
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FRACTURED 
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ZONE     IMPERVIOUS                 FILL 
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2550 
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DAM STRUCTURES 
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AUTHORIT Y 
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POWER 
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LIGHT ELECTRIC 
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PLATE   8 
SECTION 
TYPICAL 
CHANNEL 
RES 
NME T 
TRE 
ME 
APPROACH 
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INTAKE 
20 
POWER 
290 
250 
200 
2550 
VARIES  2560 
150 
TO0 
50 
120 
FLOW    POWER 
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2570 
2580 
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2610 
25590 
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2560 
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2600 
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TILIKU 
10 26 
OUTLET 
LEVEL 
LOW 
METRES 
I500 
I400 
1300 
1200 
I00 
1000 
900 
800 
200 
700 
SO0                                   500 
20o 
I00 
IO0 
RIVER 
VIDA 
40o                          300 
L HYDRAULIC                     GATE 
CHAMBER 
2530 
2550 
257O 
GATE 
SHAFT ACCES 
2590 2610F 
ELEVATION  (m) 
w 
3 
2530 
INTERCONNECTION                           TUNNEL 
CROSS-SECTION 
INTERCONNECTION                              TUNNEL 
INTERCONNECTION                            TUNNEL 
PROFILE          Ç ON 
METRES 
6.Om 
2000 
200 
400  1000  500 
2560 
500 
25575 
LINVERT        EL 
500 
o 
TUNNEL 
257002580 
ELEVATION  (m) 
RESERVoIR 
OSLFL 
EL2570.0, 
UNL 
ALELTU 
TILIKU 
F.S.L. 
OUTLET 
LEVEL 
LOW 
TUNNEL 
2600  E 
2620 
EL.2598.5 
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JIDA 
2540 
2560 
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2600 2620 
E SPILLWAY ALTHRTY 
AND 
DAM 
JIDA 
FOWER 
AND 
SHT 
ETAN 
PROFILE 
SPILLWAY EMERGENCY 
JIDA 
200 
2560 2580 
ELEVATICN   (m)    2600 2620 
400 
200 
GROUND 
ORIGINAL 
CREST 
DAM 
ORES 
SPILLWAY 
LOCATION        OF 
JD-6 
TP-
TP-JD-I         TO 
FOR 
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(LOOKING 
LINE CENTRE 
DAM           ALONG      SECTION 
SEE 
2330 2540 
2550 2560   S 
42570 3 2580     E 
2590 2600 
2000 
1900 
NOTE 1700 
METRES 
1600 
500 
400 
1300 
i200 
ONE     CONTACT 
SALT 
BA 
SSNE 
VERBUROEN 
ONE CONTAÇT 
ASALT 
TP-JD-2 
CONSTRUCTION 
TP-JD-3 
TP-JD-4         OVERSURDEN 
H 
TP-JD-I 
TP-JD-5 
BEDROCK(BASALT) 
SIAGE I 
OVERBURDEN 
WEATHERED 
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STAGE I 
TP-JD 
BED 
RIVER 
2602 0 
SECTION        IN 
EL    CREST 
DAM 
-
MAXIMUM 
NETRES 
Jzs10 
2520 2530 
2540 
20 
TRANSTON                    2ONE 
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RCNFILL               INE 
SASLT  OMAACTED 
RIRAP 
(9) 
7) 
BASALT ) 
DROCK ( 
BE 
(BASALT) 
BEDROCK 
SOUND 
LINE  -GROUT 
ZONE         DRAINAGE 
OMcTED 
(5) 
2NE INOER\S       FTLL                    ()ACTED 
FRViNs           FLL 
(3) 
((4) 
FRACTURED 
WEATHERED       OR 
FRACTURED 
BASALT ) 
ATHERED        OR 
8EDROCK ( 
WE 
ELEVATION  H2550  (m)  $ 
2560 H2570 
2580 2590 
2600 
25700 
EL   O.SL 
2601.0 
CREST  EL 
26020 
CORE 
EL    CREST 
DAM 
25935 
EL.   FSL. STRUCTURES 
CONVEYANCE 
AUTHORITY 
PROJECT       HYDROELECTRIC 
POWER 
ALELTU 
AND 
LIGHT ELECTRIC 
POWER ETHIOPIAN 
PLATE          IO 
GORGE) 
(SECTION        OF 
34  PLATE 
ALSO 
SEE 
NOTE 
POWERHOUSE 
PENSTOCK 
GORGE 
WEDEM 
METRES 
AND      TUNNEL 
200 
ZEGA 
POWER 
IN 
280 
lb+ 
I5+l00 
|4+75O 
PENSTOCK -SURFACE 
CHAMBER 
VALVE 
LINED TUNNEL   STEEL 
LINED  TUNNEL 
CONCRE        TE 
TUNNEL 
POWER 
D216O0 
1500L I600 I700 
l800 I900 2000 
2100 
200 
300+ 
E 
LINED CONCRETE   TUNNEL 
24550 
INVERT 
SLOPE 
SECTION 
CHAMBER 
SURGE 
CHAMBER 
SURGE 
¢ 
2400 
2500 
2600 
2700 
I6+28o 
SHAFT 
SURGE 
14+750 
GH 
PENSTOCK SURFACE 
2420 
2440 
2460 
2480 
2500 
ELEVATION  (m) 
LINED 
50 4t 
TUNNELI 
STEEL 
TUNNEL 
LPOWER 
t 
TUNNEL SECTION 
LINED TYPICAL 
STEEL 
SHAFT 
CHAMBER 
SECTION 
LINED  CONCRETE 
TYPICAL 
TUNNEL SECTION 
LINED CONCRETE 
TYPICAL 
VALVE 
EL24550 
IMVERT 
02 
250OO 
L 
LINED   CONCRETE   SHAFT 
METRES 
2520 
2540 
2560 
200 
E 
PROFILE 
I00              POWER 
TUNNEL 
E 
2001D 
INVERT E 
2455 O  INVERT      EL 
TUNNEL 
SLOPE 
CHAMBER 
LINED      CONCRETE 
INED CONCRETE                                                                                                                                    2580 
SURGE 
CHAMBER SURGE 
259a5 
26050 
UPME E 
EL  STATIC         WL 
MAX 
MAX 
26100 
2600 
2620 
24750 
SHAFT CONCRETE 
EL3650 
UNED 
INVERT 
EL 
RIVER ALELTU     TINISHU 
CHAMBER 
SURGE 
INTAKE 
ALELTU 
-TILIKU 
POWER 
2100 
2150 
2200 
2250 2300 2350 2400 
2450 
2500 
2550 2600 
2650 2700 ARRANGEMENT 
POWERHOUSE 
AUTHORITY 
PROJECT        HYDROELECTRIKC 
POWER 
ALELTU 
AND 
LIGHT ELECTRIC 
ETHIOPIAN 
PLATE   | 
POWERHOUSE 
SECTION         AT 
METRES 
PROFILE   PENSTOCK 
0 
SLAB - APRON 
RUNNER 
EL.I530.0 
MANIFOLD  PENSTOCK 
EL.1530.0 
POWERHOUSE 
-SURFACE PENSTOCK               MANIFOLD 
MANIFOLD 
PENSTOCK 
TRANSMISSION                      TO  LINE 
ABABA 
ADDIS 
PENSTOCK 
SURFACE 
T670 
I660 1650 
SWITCHYARD 
ACCESS          TO 
630 
1620 
I610 
PEN^TOCK SÜRFACE 
600 
-
590 
POWERHOUSE 
PLAN-POWERHOUSE 
SCHEMATIC 
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SWITCHYARD 
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TRES 
ML 
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MANIFOLD 
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I 
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UNIT I 
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UNITS                                                                                                                                                                                                                                                                 3 
SLAB 
APRON 
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AGAT 
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540 SCHEDULE CONSTRUCTION 
RS 
ENGINEERING             AND 
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REQUIREMENTS 
PROJECT       HYDROELECTRIC 
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TRANSFORMERS                  AS 
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IACONSTRUCTION                               TILIKU                        -
ROADS        ACCESS 
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MANAGEMENT 
ACQUISITION 
PROJECT     ENGINEERING            AND EGINEERING 
PRE-
4234|2   34  I234|23   234|234|234| 
234|234| 
FINANCING 
ARRANGE 
COMMITMENT PkoJECT. 
4||234|234 
T 
FEASIBILITY                     STUDY 
|234||234 
QUARTER 
QUARTER 
QUARTER 
QUARTER 
QUARTER 
QUARTER YEAR5      | 
QUARTER 
QUARTER 
QUARTEKQUARTER 
YEAR 2 
QUARTER YEAR4 
QUARTER 
YEAR 4 
YEAR 3 
QUARTER                      QUARTER 
23 
QUANTITIES 
YEAR 7 
YEAR 6 
YEAR 3 
COMMITMENT 
PROJECT 
YEAR 2 
PRE 
YEAR | 
PRINCIPAL 
DESCRIPTION 
I0  YEAR 
YEAR 9 
YEAR 8 
CONSTRUCTION 
YEARI 1 
TDSUC     DATE DUE      AUTIHOR        ZCPA 
TITLE 
ATOtot 
VOLUME.........        NO...       CAcc. EDITION. 
TITLE        AUTHOR 
BORROWER'S  NAME 
CALI. NO 
CALL   NO.

Summery

Aleltu Hydroelectric Project Summary

Aleltu Hydroelectric Project - Executive Summary

Project Overview

Location: Approximately 60 km north of Addis Ababa, Ethiopia

Study Date: June 1984

Conducted by: Acres International Limited for Ethiopian Electric Light and Power Authority (EELPA)

Financing: Jointly funded by Canadian International Development Agency (CIDA) and EELPA

Key Findings

Reconnaissance Study

Identified 14 subbasins with theoretical potential of 3,800 GW·h/yr
Economic potential: 3,600 GW·h/yr from 12 subbasins (1,020 MW at 40% load factor)
Recommended staged development concept with interconnected reservoirs

Prefeasibility Study (First Stage)

Recommended first stage: Tiliku Aleltu (300 MW) followed by Jida development
Generation potential: 1,040 GW·h/yr firm energy
Estimated construction cost: $407 million (1984 dollars)
Unit cost: $1,357/kW capacity, 47.1 mills/kW·h energy
35% lower unit costs compared to Gilgel Gibe alternative

Project Components

Component	Description
Tiliku Aleltu Dam	Earth- and rock-fill dam (54m height), 92 Mm³ reservoir
Jida Dam	Earth- and rock-fill dam (65m height), provides 90% of Stage I storage
Power Tunnel	Concrete-lined, 16.3 km length
Powerhouse	6×50 MW units, located in Zega Wedem Gorge
Transmission	230 kV line to Addis Ababa

Implementation Schedule

Feasibility study recommended to start by end of 1984
First units could be online by January 1993
Construction duration: 5.25 years from commitment to first unit

Recommendations

Proceed with feasibility study for first stage development
Install additional streamflow and rainfall recording stations
Continue data recording at existing stations
Obtain 1:50,000-scale mapping of project area
Confirm reservoir integrity at dam sites

Economic Analysis

The project compares favorably with alternatives, showing:

35% lower unit costs than Gilgel Gibe
Favorable location near Addis Ababa
Staged development potential matching load growth

Environmental & Social Considerations

500-600 families potentially affected by reservoir creation
Most homes located on ridges will not be flooded
Rehabilitation programs considered for affected farmers
No major environmental barriers identified