Aleltu Hydroelectric Project Summary

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Ethiopian Electric Light & Power Authority
Aleltu Hydroelectric Project
Reconnaissance and Prefeasibility Studies
Volume 1 - Executive Summary
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i   LL Acres International LimitedEthiopian Electric Light & Power Authority
Aleltu Hydroelectric Project
Reconnaissance and Prefeasibility Studies
Volume 1 - Executive Summary June 1984
Acres International LimitedVOLUME 1
VOLUME 2
- EXECUTIVE SUMMARY
-   MAIN REPORT
VOLUME 3 - APPENDIXESJuly 19/ 1984 P6888.03.01 
.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
Pre feasibility Study
We       submit       herewith       the       final       report       on       the       above       study       whies 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 a:
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 tne
recommended feasibility study; these are
-           install        additional        streamflow        and        rainfall        recording 
stations in the project area suooasins immediatelv
-        ensure      that      continuing      recordings      are      ceing      made      at      all      of the   me   t   eo   r   o   1   og   i   c   a   1   and   streamflow   recordinc   stations   '   a*' around tne Aleltu project area
- ootain 1:50 000-scale
mapping of tne entire project area.ACKNOWLEDGMENTS
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.VOLXME 1 - EXECUTIVE RJRRXM TABLE GF OOKTEXT5
GLOSSARY CF ABBREVIATIONS LIST CF TABLES
LIST CF PLATES
PREFACE:
1  - CONCLUSIONS
2   - RECOMMENDATIONS
r»M*
1  - INTRODUCTION---------------------------------------------- --
1.1     - General -------------------------------------------------------------------------------
1.2     - Terms of Reference and Scope of Work ----------------------------------------
1.3     - Background---------------------------------------------------------------------------  •
1.4     - Study Execution ---------------------------------------------------------------------
2   - RECONNAISSANCE STUDIES -------------------------------------------------------------
2.1     - General--------------------------------------------------------------------------------  5
2.2     - Extent and Concept of Development ---------------------------------------------
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-------------------------------------------------------------------------------------  ^5
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
3.5       - Socioeconomical and Environmental
Assessment -------------------------------------------------------------
3.6       - Project Layout Alternatives ------------------------------------------------
4   - DESCRIPTION OF RECOMMENDED FIRST STAGE
DEVELOPMENT OF THE ALELTU PROJECT --------------------------------
4.1       - General -----------------------------------------------------------------------
4.2       - Basin Geology ---------------------------------------------------------------
4.3       - Tiliku Development --------------------------------------------------------
4.4       - Interconnection Tunnel and
Low-Level Outlet ----------------------------------------------------
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 7.2       - Timing
Project Generation Capability ----------------------------
of Plant Additions ------------------------------------------
8 - ECONOMIC ANALYSIS -------------------------------------------------------------
8.1      - Value of Capacity and Energy
for Stage I of the Aleltu Project -----------------------------------
8.2      - Alternative Developments for Comparison —
8.3      - Comparison Between Aleltu and
Gilgel Gibe ----------------------------------------------------------- PLATES
31
31
33 37
37
37
38VOLUME 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
ERE SA           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
plant factor
PI
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
1
2
3
4
5
Title
Basins and Drainage Areas
Power and Energy Capabilities of 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 ScheduleKi tin lh ‘M .'A M
- l & Jit-ill - • ‘ll *L •
PREFACE
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.practical first stage of
4     - The most economic an P
.                Tiliku Aleltu scheme, followed development is the Tin^
by the- Jida scheme.
5     - Future schemes for implementation are
-    Weserbi (plus possibly Girar and Gur)
-   Gomoro
-   Robi
-    Chacha
-    Duber
-   Robi-Gomoro
-   Jinjer
-   Sibilu.
Prefeasibility Study
€     - 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.
There are no social or environmental factors which shoulc prevent implementation of the Aleltu project.
ea
sjtstctior., engineering owner's acmi
socioeconomic
costs, 
contingencies, 
eno construction management, and n.stration of Stage I of the Aleltu(iii)
10 - Based on construction costs
and substation costs at the
- the unit cost of capacity
(including load center)
is US $l/357/kW
transmission 
— the unit cost of available finn energy is
47.1 mills/kW-h (at 12% discount rate).
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.(iv)
Allowing for normal financing, engineering construction periods, the feasibility studv
• 
be started at least 8 years in advance of £be
required on-line date. If the studies were
S^Oii] .
before the end of 1984, the first units com     d 
3rte
,. 
. 
uu la
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 1:50 000-scale mapping of the entire project area
4 - carry out investigations to confirm the reservoir integrity ct the Tiliku 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) wa engaged to perform the study jointly witn professional and technical staff of EELPA.
* Power Planning stu dv, October 1982. 
“
Acres International Limited,2 
1.2  -  Terns  of  Reference 
and  Scope  of Work 
The  Terms  of Reference and  General  Scope  of  Work   can  he sumarized  as  follows. 
-  Undertake  an  initial assessment  of  the Aleltu  Basin   2 reconnaissance  level  to define  the  ultimate hydroelect:. 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 
system  (ICS). 
The   installe    capacity  of  the  Main   ICS   is presently 213.7  MW. 0f  this,   97     is  provided  by  four  hydroelectric  power  plants, namely,  Koka,   Awash   II,  Awash   III and Finchaa. 
The   Amarti   iversi  on    and Malka  Wakana   projects  are  presenty 
under  construction. 
these  projects  (in  1987) will  be   348.5  MW     of  dependable capacity  an     1,760   Gh/yr of  firm  energy . 
The   crowing  economy  and   electrification  orograms  will  demand increasing  supply  of   power   and   energy.    The   1982  PPS   shows 
The   ICs  capability after completion  of 
that  there  wil1   be 
de pencing  on   the  l0&0 
a need   for  additional  generation, 
1993. 
forecast  assumed,   petween   1989   &nd 
eveiopment 
EOr     t he  1990s   an   into  the  nExt 
prograr  ior  th  ICS   will  be 
century,  the   optinuT 
prinarily  hyaro. 3 
Ethiopla has  a  large  number  of  potential located  in  the  Omo  and  Blue  Nile  basins. 
developments,  malnly 
The  most  prOmising 
developments  were  found   to  be   the Aleltu  and Chemoga   develop ments  in  the  Blue  Ni le  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  l,100  m 
potential  generating  capability  up   to 800   MN 
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   stuay  was   executed  in  two   phase s--reconnaissance and prefeasibility--duri ng  the  period  from  July  1983   to  issue  of the  final  report  in  June  1984.     Field  investigatins  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  o£  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, Piche  to  the   northwe st 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. 
drainage  basins  and 
potential  ultimate evelopment    of 
Plate  1   sh0ws  the 
the  Aleltu  project. 
presently  discharge  into  four  larger river basins. These  are 
The  rivers of  the  14   subbasins 
Zega  Wedem,    in  the  northcentral  part   of  the  project 
area 
-   Bersina,  northeast  of 
Giamma  to  the  east 
Muger  to  the  west. 
the  2ega  Wedem 6 
These ma jor 
basins, toge 
ther With the subbasins 
their drainage areas, are 
shOWn ln 
Table 
and 
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)  locate upstream  from  the  Zega  Wedem  and  Bersina gorges  and  sL 
high  head  that  can  be  developed  in  these  gorges, 
The 
major  part  of  this  head   is  trom  the  edge  of  the  plateau 
to  the  bottom  of  the  gorge. 
Plate  2  showS  sections 
along  the  Zega  Wedem  and  Bersina  gorges. 
In  both 
of  western  basins  and  one 
gorges ,  the  potential  head   increases  to  the  west  going away   from  most  basin  developments. 
From    a stuiy  of  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  RObl. It was   therefore considered  that the reservoirs  in 
these   basins  could probably  be  interconnected  with  low cost  uncontrolled  channels  or  tunnels  and  operated  as an integrated  network  with  a common   reservoir  level. 
From  the interconnected  reservoirs.  a  power  tunne 
canal)  and  penstock  could  convey  power  flow  to  a  common powerhouse  located  in  the  Zega  Wedem  or  Bersina  gorges. 
Alternatively,  more   than  one   powerhoUSe    could be considered;   one    in   the   Zega    Wedem    Gorge   for   development 
eastern basins. 
in  the  Bersina  Gorge    ro 7 
TABLE   1 
BASINS  AND  DRAINAGE  AREAS 
Major Basin 
Zega Wedem 
Subbasin No.* 
2 
3 
4 
6 
7 
Bersina                   10 
Muger 
11 
12 
13 
Giamma                            14 TOTAL 
River 
Gur 
Weserbi 
Agat 
Tinishu Aleltu Tiliku Aleltu Jida 
Robi-Gomoro Gomoro 
Robi 
Jinjer 
Girar Duber Sibilu Chacha 
Drainage Area ** (km2) 
93*** l68 
86 
77 
458 
749 272t 225 
437 
238 
312 
172 
518 
590 
4    395 
The subbasins are  numbered  from  west  to 
south,  starting  with  the  Gur, which  is 
east  and  north  to 
the  most 
Dr ainage areas 
northwesterly  basin. 
each  river. ***Excluding   the 
Weserbi   tributary. 
correspond to  basin  area  at main  damsites  on 
Dr 
ainage area  is  doWnstream  from   RObi and  Gomoro   sites. Basins distant  from  the 
gorges  and those not  Suitable 
developing as part of 
the integrated 
netwOrk  could 
for 
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  l:250  000-scale 
mapping  with  interpolated  50-m 
contour  intervals. 
Mapping  at l:50  000-scale with  20-m 
contour  intervals 
is available  over  that  part of  the  project  area  west  of 
longitude   39°00    (see  Plate  l). 
This  covers  about  one 
third of the project area.    The  l: 250   000-scale mapping is  not  adeguate  for  reconnaissance  or prefeasibility level  stu£ies,  and  therefore  the available  mapping. was supplemente£  by  extensive  ground  surveys   carried out  by EELPA. 
2.3.2 -  Hyarology  and 
Reservoir Studies 
Hyårologic  studies  of  basins  in  the  Aleltu project  area were  undertaken  to assess 
-  the available  flows  for hydroelectric generati on 
the  required  reservoir  vol umes  (and  dam  heights) at varying  degrees  of  flow  regulation  for  separate  and integrated  reservoir operation 
-   the  flood  flows  which  will  govern  the  design  of iversion    worhs  and  spillways, 9 
1 
2.3.3 -  Geological Assessment 
Regional  and  local geological  conditions  were  assessed in  the  Aleltu project area  for  the  purpose  of  des igning structures  (at  reconnaissance  1evel),  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,   includinc  dam 
locations, reservoir  sizes,  interconnection  tunnels  Or  oven channel  conveyance   structures, power  tunnel,   penstoc   rOutes development options. 
and   powerhouse 
10 
locations, provides for  a  large  number  of 
special 
approach  was 
Initially, 
alternative, 
development   options 
required to 
address these  options. 
for  the  basins 
and 
the 
poOwerhouse 
location  were 
screened to  identify the  most 
promising schemes. 
analysls was 
followed 
extensive use of a  layout optimization 
The   screening 
model. 
2.4.1 -
Description of 
Optimization Model 
Layout 
The  layout 
optimization  model, developed  for  the Alele.. 
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 These  are 
dans 
interconnection tunnels power  tunnels 
-   penstocks 
-   powerhouses. 
2.4.2 -  Long-Term  Grid Energy  Supply  Cost 
on  project  economics, 
The  economic  críiterion  used  in  the  layout   optimizatio model   is that the  incrementa1  cost of available  energy supplied  by  the  kleltu project schemes  must  be   leS5 than  35  mills.    This cost excludes  construction  camp 
and  facilities,  contingencies,  management  engineeri ng, 
owners  cost   and interest  during  construction. 11 
Thìs  parameter  was    derived from  the   19  82   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. study  yielded  a  clear definition of  the  ult ima te development concept of the Aleltu project. 
The 
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 schenes 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 
Site  A. 
powerhouse 12 
There are three diversion 
schemes which the 
reconnaissance  study  has 
evaluated  to  be    economic, 
namely,  the 
Weserbi, Duber and  Chacha. 
Four  other 
have   been identified as  diversion   schemes   but   have 
basins--Gur,  Girar, Jlnjer and   sibil, 
not  been evaluated. 
These   schemes   are  expected  to  be 
developed  at  a later stage  of  the  Aleltu project  ana do   not   affect  the conclusions  of   the   reconnaissance 
study. 
2.4.4  -  First Stage  and  Ultimate 
Developnent  of  the  Aleltu  Project 
From  the  stuay  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 
the  £irst stage  of construction. The  Tiliku  Aleltu  and  Jida  schemes 
part  of 
first stage  of  the  economic  potential  of  the  Aleltu 
would  only  be  the 
project. 
expected 
to  be 
The   development  of   the  ultimate  project  is 
as  follows 
- Stage  IA  - Tiliku  Aleltu 
-  Stage  IB   -  Jia 13 
-    future  stages 
(a)    Weserbi   (plus  possibly Girar  and  Gur) 
(b)    Gomoro 
(c)     Robi 
(a)      Chacha 
(e)    Duber 
(f)    Robi-Gomoro 
(g) 
Jinjer 
(h)     Sibilu. 
The  overall  arrangement of  the 
ultimate  development  is 
1 
shown  on  Plate  4.     The  energy  and  capacity additions for  this seguence  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   1,0 23  MW     (at  40%   load  factor). 
This  capability 
Would meet  ICS   load  demands   (for  the  standar£ load forecast  including  boilers,  anã  implementation  in  the mid-1990s)  for about  15  years. 14 
TABLE   2 
POWER   ANO   ENERGY CAPABILITIES  OF   STAGED 
ULT IMATE  ALELTU  DEVELOPMENT 
Fim Energy  (GH.h) 
Devel opment 
Stage  lA 
TIlku Aleltu*# Stage  I8 
Jida** Future  stages 
-  Weserb| *** 
-  Gomoro 
-  Robi 
-  Chacha 
-   Duber 
-  Girat* 
-  Gur+* 
-  Robi-Gomoro 
-  Jinjer 
-   Sibi lu 
AddItlons 240 
763 
Accumu latlve 
Additlons 
hccumulative 
240 1 003 
) 
) 
)286 
286 
168 189 
317 
458 298 172 
93 220 156 518 
1 171 
1 360 
1 677 
2  135 
2 433 
2 605 
2 698 
2 918 
3 074 3  592 
) 
) 
48 
5 
90 
131 
85 
49 
27 
63 
45 
148 
Installed Capacity at 
40% Plant Factor  (MW)                 Average  Cost  of Pro (ailIs/knh)          ject  Energy' 
34.6 25.6 
25.1 
25.0 
24.2 
23.8 
24.2 
334 
385 
475 
606 
691 
740 
767 
830 
875 
1 023 
+* 
NoTe  That 
Note  that data 
corresponding  long-term  grió  energy  supply  cost  is  35  mi    l ls/k*ne 
***Girar  and  Gur   could  be   incorporated  in  development  of   heserbi. 
study. 
for  Ti l i ku  Aleltu  and   Jida   will change  sl ichtly  in   the   prefeas ibiIy 15 
3   -     PREFEASIBILITY  STUDIES 
3.1 -   General 
In  the  reconnaissance   studies, the  Ti1iku 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   construct ion 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 stu£ies  were  carried  oUt  to  establish size  and  operating  requirements  of  the  project structures. These  comprised 16 
-  runoff and  rainfall data analyses determination of monthly  inflow sequences 
calculation of 
reservoir evaporation effects 
deternination of 
assessment of potential reservoir sedimentation 
reservoir requlation requirements 
-  flood  flow  analyses 
reservoir routing  calculations. 
Stucies of  particular significance to  the  operation of  the project were  as  follows. 
Inflow Sequences 
Because  of  poor  historic correlations  betwe en  the  rainfall and runoff  records  of  gauging  stations  in  and  around  the 
project  area,  inflo sequences  were  derived  utilizing synthetic methoás  and  were  base    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  m/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  an     Geotechnica1 
InvestiçatiOns 
The   geological  anc  geotech1ca)  i nvestiçation  program  at  th prefeasibility level  wes   carried out  to 17 
assess  foundation  conditions 
locate natural constructíon materials 
determine  design  requirements  relating to materials and seismic  conditíons. 
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 Tíliku 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  identi£ied.    A  Summary  of  their description is  included  on  Plate 5. 
3.5  -    Socioeconomical  and 
Envionmental 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 
-    identi fy   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,   farns,  towns   and   villages, historical  religious  centers  (particularly  Debre  LiTanos), health  and  Wildlife  were  evaluated. 18 
The  significant impact arises from creation of the reservoirs. 
With  the  extensive agriculture  in 
the area, 
considerable 
farmland  wil1  be  inundated  by  the reservoirs. 
The  areas of 
the Tiliku Aleltu and Jida reservoirs are  7 
and  52  kmz, 
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  farnlands  and  compensation  by   support programs 
-  a  fertilizer program  for existing lanis  and  an  equipment support  program 
-   a   resettlement  program. 
3.6  -   Project Layout Alternatives 
The  general  arrangement  of  the first stage of  the  project was establisheá in  the  reconnaissance  studies. 
In  the  prefeasibility stage,  layout  studies  were   conducted to produce  a  functional  project  in  accordance  with  good   hyiro electric engineering practice.    Significant considerations  in the project layout were 19 
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 
1 
4.1 -   General 
The   first  stage  development  of  the  Aleltu  pro ject  would Consist of 
-   development  of  the  Tiliku Aleltu   and Jida  river basins 
instal1lation 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  dams ites at  eleva tions within  the  reservoir.    Groundwater  seepage  and   springs have  been  observed  in  the  valley  slopes  on   the  alignnent  of these  contact  2ones,    ThËs   Seems   to  suggest  that  the  coneact Zone   is  Water  bearing  and    perme able. 22 
Tne  geological weaknesses  resulting  from  the  weathered Contact  zones    may    comprise   potential seepage  paths   and,   if 
extensive, these   would require  treatment   to curtail 
To   cope   with   any  potential seepage   paths,  provision 
leakage,    been 
has 
nàde  in  the  layout  design  and   cost  estimate 
-   to seal  these  areas  (with  an   inperv10uS  blanket,  grout  or other   method) during  the  construction  period 
-   if required,  to  draw  the  reservoir  own     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 wicth  irom  about  400           ide  at  the  narrowest  section  (am 
location)  to 4 kI vide  at  the  widest   section, and  a  total 
reservoir  volune  of  92   Mm,   at an   PSL   of 
Storage  at  FSL   is  90   M3, 
2,598.5  m.       Live 
maxium   availasie, being 
linited  by   topography,   and  will  only 
This  live  storage  volume   is  the 
provie     for   about  604 
regulation  of   the  natural  inflows. 
Ar.    earth-  &nt   rocr-fil1  dam 
S1te.    The   mY.iur  height  oí is the provided  at the  Tiliku  Aleltu 
poirt  of   tie sedrocr.  iouncatior.. 
 am  is  54   m above   the  lowest 
are  sNoWr   o. Plate  7. 
Tyoical  sections  of  the  dat 
Wit     the  bast1t  eCrocr,  ioundation  conditicns  are  adeguate 
for   construCLI0n  C:     2  ért- &nc   roch-fili   dam. 23 
4.4      Interconnection  Tunnel 
and   Low-Level  Outlet 
The   Tiliku Aleltu and  Jida  reservoirs  are   interconnected by 2  km   tunnel,  and   both   reservoirs operate  the  same   level. 
low-level  tunnel  is  provided  for  emergency  árawáown  of  tne 
two  reservoirs  to  inspect  the  dams  or to  expOse  the  basalt Contact  zones  in  the  lower elevatíons of  the  reservoir,  if necessary.    The  low  level  tunnel  is  taken  off  the interconnection  tunne1  between  the  two  reservoirs,  as  Sho. on  Plate  6    and Plate  . 
4.5  -   Jida  Development 
The  Jida  reservoir  is  considerably larger  than  that of Tiliku Aleltu.  It wil1  be  approximately  27  k  long  and  4  ka wiie  2t 
its broadest point. 
The  Jida  reservoir vill  provide  about 
1 
90%   of  the  tota1  live storage  for  the stage  I  development. 
The   other  10    wil1  be   provide    by   Tiliku Alel:u.    Full 11o regulation  for  both  the  Tiliku Aleltu  and  Jida  rivers   inilo will be  achieve    at  FSL   Of   2,598.5  =  corresponding  10  a  live storage  of  990   Mm3. 
Similar to the Tiliku Aleltu schene ,    an earth and rock-ill dam   is  provided  at  Jida.    Cres.  eleva:10ns  are  the sare ior both   dams, but  max inun heigh:       the Jiia an is  65     2b0ve the  lowest  point  of  the  bedreck  founcaion  wnicn  is  11 higher  than Tiliku Aleltu. 
Typical   sections  o  he  ma in  dan   and  cofiercan  in     n riverbed  are  snown   on   Plate  9. 24 
4.6 - Dam  Construction Materials 
The  dams  at Tiliku 
Aleltu and  Jida have  been  designed ta 
maximize  the  use  of 
local materials. 
The  vol umes  of 
materials required for the two  dams  are as follows, 
Tiliku 
Material 
Compacted  impervious Compacted  filter Compacted  transition Compacted  rock  fill Riprap 
TOTAL 
2one 
1 
7 
9 
Aleltu (Mn3) 
0.15 
0.07 
0.18 
0.56 
0.04 
1.00 
Jida 
(Mm3) 
0.90 
0.40 
0.88 
4.79 
0.15 
7.12 
In  general,  with  the  exception  of  transition material, adequate  supply of  materials  is available  from  natural sources within economic  hauling  istance    of  the  damsite. 
The  source  for the  transition material wil11  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  l10.       It is expected  that  the  rock  quality  in  the  upper  basalt  and   in  tie lower  agglomerate  will  be   of  good   quality,  except  in  local areas  where  the   tunne l  Crosses  any   flow   contacts  or   discOn tinuities.   The   basalt,  however, could  have   extensive 
eienificant  structUrel  or 
fractures  and/or  be   heavily  fissured. 
construction  problems   but  may 
This  would   present  no 25 
provide  leakage  paths  for  the  power  flow. 
There fore, 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  reguired  to  stabilize  the  rock. 
4.8      Penstock 
The  surface  penstock  will  be  constructed  of  high  strength steel  extending  from  the  termination  of  the  power  tunnel,  in 
the  agglomerate  zone,  to  a  manifold  at  the  powerhouse. 
The 
manifold wi1l  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  O£, 
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 to  the 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  l4  kn  down  the face  of  the  gorge,  as  shown  on  Plate  6. 
ATION 26 
4.10      Switchyard  and Transmission 
The    switchyard will  be   located  on upstream  from  the  powerhouse,  with 
a terrace  above  and 
orientat1on convenient  for 
Connections  from  the  powerhouse  and  the  outgoing  1ines, From  the  Aleltu  switchvard,  a 230-kV,   double-circuit trans mlSSion  line  comes  off  the  dead-end  towers  and  1s  routed  up 
the  gorge  alongside  the  penstock. 
From   the  top  of  the  gorge, 
the  11 ne   runs  due   south  cross-country  over  the  plateau  to #ighway   3 south  of  Debre  Tsige.    From   this   point, the  line generally  follows  the  highway  to  Addis  Ababa. 27 
5   -   CONSTRUCTION  PLANNING 
1 
5.1      General 
Several  of  the  structures wil1  require specialized con tractors, such  as  for   the long  power  tunnel,  steel penstock and  the  access  road.    However,   these  same  structures  are convent.ional  in design  and  simi lar in size to other hydroelectric  projects  in  Ethiopia  and   internationally. 
It  has  been  assumed  that  one   ma in 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 equi pnent  and the  transmission lines would  be  contracted  by   competitive tendering  from  international  manufacturers. 
5.2  -    Construction  Schedule 
An   engineering  and  construction schedule  tor  the  Aleltu hydroelectric  project  is  shown  on  Plate  12. 
Stage  I  construction of  the  Aleltu  developme nt  has  300-MW installed capacity.     This construction  1s  carrled out  in  two periods,    Stage  IA  1S   the Tiliku Aleltu development  with three  50-MW   units  installed.    Stage  IB   1s  the  Jida develop ment   tor  which  an  add1t ional  three  50- MW    units  wOuld  be instal led. 
The   tI me      from  project  cOnniC ment   to  flrst  unIt  on-lne  ior constr uction Stage  IA   LS    5.25  years.    Units   2  and  3come on-11ne  at l.5-mo Lntervals  tnereatter.    For   Jida,   the 28 
construction schedule  depends  on  the 
ICS   requiremens 
standard  load fore cast,  including boilers  and  assumi ing   no 
For 
the 
ICS  regulation  for  the Tiliku Aleltu flows,    Unit    4  (which   is part   of    Stage  IB)   comes   on-line  l.5 years  after the  first 
unit.    Units  5  and  6  follow at  l. 5-mO  intervals, 
If  other 
reservoirs  in the  ICS  can  provide 
regulation for Tilik, 
Aleltu   flows ,  then Stage  IB  Could  be 
delayed  with  Unit  A 
coming  on-line about  2.75  years after Unit l. 
The  ICS 
Project  Power   and   Energy 
requirenents  are  discussed  more   fullv  in   Sect 
Capability  in  the  ICS. 29 
1 
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    premi um   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 naterials, and  any  Ethiopian taxes  on  contractors!  and consultant' s   revenues  and  salaries have  not  been  included. 
Interest During  Construction 
Interest during  construction ,  at l28/yr,  amounts  to 
US    ^106,960,000   (26.3%  of  the  construction cost).    The investment  cost  (in  1984  do1lars)  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 
escalation, 
excluding 30 
TABLE  3 
STAGE   I 
PREFEASIBILITY  CoST  ESTIMATE (6x50-MW     Units ) 
Item 00 01 02 
03 04 05 
06 07 08 09 10 
12 
Description 
Infrastructure 
Reservoir 
Interconnection  tunnel (including low-level outlet) Dams   (Tiliku Aleltu  and  Jida) Spillways  (Tiliku Aleltu and    Jida) Power  intake 
Power  tunnel  (including  surge and valve  chambers) 
Surfce penstock Powerhouse  (including electro mechanical  eguipment) Switchyard 
Socioeconomic Transmission Gafarsa  substation 
Subtotal 
Engineering  and  construction management Owner's  administration 
TOTAL   CONSTRUCTION   COST 
January  1984 US   Dollars* 
58,940 ,000 
2,100 000 
12,750 ,000 
99,960,000 
4,780,000 
2,690,0 00 
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 
2c2   cost  item  nCludes  1ts  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 
-   l80 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 coula be  used  to  firm  up  secondary  energy  generated  by   the Tiliku 32 
TABLE 4 
ALELTU PROJECT POWER AND ENERGY CAPABILITIES 
Tiliku Aleltu 
Description 
Annual fim 
Unit 
GW h/yr 
As An Isolated 
Plant 
260 
With Requlation* 440 
Ji da t* 620 
Tiliku       and  Jida Aleltu 1 040 
energy 
production                                               150                           150                   300 
Installed capacity 
Secondary energy 
capability 
MA 
GW"h/yr 
150 
180 
10 
10 
20 
"  180   Gi "h/yr of 
ICs reservoirs 
perforrance of  Jia     is  the 
Or   by   Jia 
reservoir. 
seconary 
energy   firned up  by  existing 
ICS    regulatioa, because 
&s   an isolated 
of  the 
sane  operating 
lar ge   stora ge 
a vailable 
plant or with Ji da. 
at 33 
Aleltu  scheme   (or  Gilgel  Gibe 
ing  capability  is available 
at  the  time  of  implementation  of 
project).    If this  ICS 
regulat 
the  Aleltu project ,  then  the  Jida  scheme 
come   on-line  much   later  than Tiliku Aleltu.     (This is 
could  be  delayed  to 
discussed  more   fully  in  the 
next  section.) 
It is  noted  that  the  additional  ICS   regulation  potential  was 
ment  of  the  Aleltu  project  in  this  study.*    However, develop          it is 
not  taken  into account 
in  sizing  of  the  first stage 
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 nost,  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  Ji£a,  the 
and  the  two   schemes  combined  are  therefore 
project will meet  any  expected   load for  more   than  6 
years, 
consider  as  the  first  stage  of development. appropriate  to 
*It  is 
should 
considered  that 
level  of 
not  be 
study  since generation  plans  and  the  character  of 
taken  into 
the  regulation  capability  of  the  ICs 
the  ICS 
may   change  before  implementation  of  Aleltu  is 
account  at  this prefeasibility 
realized. 34 
TABLE   5 
ALELTU  PROJECT 
SYSTEM  SUPPLY  CAPAB IL ITY 
Abiiity to 
Sat Isfy Load   Demand   (in  years) 
Forecast  Scenar io 
Standard  forecast including  boi lers 
Low    forecast 
includ i ng  bol lers 
Standard  forecast exclud i ng  boi lers 
Tiliku Aleltu Without ICS  Regul  at ion 
Capacity 3-3/4 
Energy 
1-1/2 
TUIku Aleltu with ICS  Regu latlon 
Capacity  Energy 
TUiku Aleltu Plus  Jida 
Capacity 
5-1/4           2 
4-3/4 
2-1/4 
3-3/4 
5-1/4 
4-3/4 
2-3/4 
3-1/4 
3-1/2 
9-1/2 
Energy 
7-1/4 
7-3/4 1 
1 
35 
-   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  wil1l  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 
de  ferred  fo      this  same  period.    That  is,  Jida  would  follow Tiliku Aleltu by  2.75  to 3.5  years. 37 
8- ECONOMIC    ANALYSIS 
1 
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    $1,357/kW 
-   the  unit  cost  of  available  firm energy  is 
US    S47.1  mills/kW.h  (at  l2%   discount  rate). 
8.2  -   Alternative  Developments 
for  Comparison 
Alternative  projects  to Aleltu  were  ientified    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  stu£ied  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  censtruction at  this date,  it is  considered  an   appropriate  project  for  comparison with Aleltu since 
-   both  Aleltu  and  Gilgel  Gibe  are  oi  comparable  size 
both  project  studies  are  current 
-   both  projects  are  for  implementation  in  the  ICs. 
The   pOwer   characteristics  of  Gilgel  GiTe  ani  Alelt   are  as follows. 38 
Aleltu Stage I 
Unit 
Dependable  capacity   MW Plant  factor 
Minimum  net  head Firm  energy Average  energy 
GW"h/yr 
GW"h/yr 
300 
40 
1 009 
040 
1 060 
Gilgel  Gibe 
285 25 
230 670 820 
8.3  -   Comparison  Between 
Aleltu  and Gilgel  Gibe 
There  are various  differences  in  approach  tO  the  developnent 
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 Comnon  base. 
The   following  table  contains  the  comparison  of  unit construction cOsts  of  capacity  and energy. 
Power  Station 
Aleltu 
Gibe   Gilgel (adjusted) 
Aleltu Lower  than Gilgel  Gibe 
8) 
Plant  tactor () 
Installed capacity  (MW) 
Firm energy  (Gh"h/yr) 
Total  construction cost  ( USS  mi1lion) 
40 
300 
1 040 
407 
Unit  constrUction cost 
-   USS/kn   (installed ) 
-   USS   Lills/kin (available  firm) 
1,357 
47.1 
40 181* 670* 377 
2,083 
71.6 
65 
66 
2ASEc  on 
calculate  CEpencabie 
acjusting  neao   0seG   1n 
cpecity 
èna 
Gilgel  Gibe 
fir:. 
energy. 
study  to 39 
AS    indicated  in  the   table, the  first 
project wil1  be   about  35% 
lower  in  unit costs  than  the 
stage  of  the  Aleltu 
proposed  Gilgel  Gibe 
that,  based  on   this  comparison,  the  Aleltu  project  appears  to 
development. 
It was   therefore  concluded 
be  highly 
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FOR ETHIOPIAN  VALLEYS  DEVELOPMENT STUDIES   AUTHORITY 
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DATE  DUE DATE  DUE 
ACC.D01 
C.N  3 
CALI. NO 
AUTHOR     Aleltu-hydroetectric.--oroiect..recann 
AUTHOR 
ELPA 
TITLE 
reconnaissance  and  prefeasib|lity studies 
CALL NO. 
Aleltu hydroelectric project 
Copy  No. 
EDITION.. 
VOLUME. CAce.    NO.

Summery

Project Overview

The Aleltu Hydroelectric Project is a major hydroelectric development study conducted for the Ethiopian Electric Light and Power Authority (EELPA) by Acres International Limited in 1984. The project is located about 80 km north of Addis Ababa.

Key Findings: The study concluded that the first stage development (300 MW) is technically and economically very attractive, with an ultimate development potential of about 1,020 MW from 12 subbasins.

Project Components

Stage I Development: Tiliku Aleltu (3×50 MW) and Jida (3×50 MW) schemes
Power Generation: 1,040 GW·h/yr of firm energy
Head: Approximately 1,100 m
Reservoirs: Tiliku Aleltu (92 Mm³) and Jida (990 Mm³ live storage)
Powerhouse: Located in Zega Wedem Gorge

Economic Analysis

Metric	Value
Total Construction Cost (1984)	US $407 million
Unit Cost of Capacity	US $1,357/kW
Unit Cost of Firm Energy	47.1 mills/kW·h
Comparison with Gilgel Gibe	35% lower unit costs

Key Recommendations

Proceed with feasibility study for first stage development (Tiliku Aleltu and Jida)
Install additional streamflow and rainfall recording stations
Continue data recording at existing meteorological stations
Obtain 1:50,000-scale mapping of entire project area
Investigate reservoir integrity at Tiliku Aleltu and Jida sites

Project Timeline

If studies began before end of 1984, first units could be online by January 1993. Construction would take approximately 5.25 years from commitment to first unit online.

Environmental and Social Considerations

The study found no significant environmental or social factors that should prevent implementation, though about 500-600 farming families would be affected by reservoir creation. Rehabilitation programs were considered including land redistribution and resettlement options.

Ultimate Development Potential

The ultimate development would include 12 subbasins with total installed capacity of 1,023 MW and firm energy generation of 3,592 GW·h/yr. Future stages would include Weserbi, Gomoro, Robi, Chacha, Duber, Robi-Gomoro, Jinjer, and Sibilu developments.