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December 2015
Japan International Cooperation Agency
Kokusai Kogyo Co., Ltd.
THE PROJECT FOR GROUNDWATER RESOURCES ASSESSMENT IN THE
MIDDLE AWASH RIVER BASIN IN THE FEDERAL DEMOCRATIC REPUBLIC OF
ETHIOPIA
FINAL REPORTGEOLOGICAL AND HYDROGEOLOGICAL MAPS
The Federal Democratic Republic of EthiopiaMinistry of Water, Irrigation and Electricity
Composition of the Report
Executive Summary
Main Report
Supporting Report
Data Book
Geological and Hydrogeological Maps
This Report is prepared based on the price level and exchange rate of July 2015. The exchange rate is:
US$1.0 = ETB20.6298 = JPY123.80
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Lake Ziway
Lake Koka
Lake Yardi
Lake Ertele
Lake Abijata
Lake DendiLake Ala Semite
Lake Wenchi
Lake Dalay
Lake Goletsho
Awash Wenz
Abay
Ramis
J ema
Bilate Wabe Shebele Wenz
Wechti Wenz
MugerW
enz
Addis Abeba
Nazret
Yilu
Gola
Lemi
Mine
Guna
Meki
Dera
Kula
Rago
Bube
Robi
Hobe
Bu-i
Teji
Ambo
Doba
Erer
GotaBike
Hirna
Wanje
Akaki
Chole
Iteya
Arara
Suten
Ada-a
Kibet
Deder
Asela
Ramis
Ziway
Magna
ModjoHmero
Harew
Sheno
Fiche
Robit
Sagure
Diksis
Arerti
Agemti
Molale
Sodoma
Merewa
Woliso
Huruta
Hujufa
Tibila
Koshim
Ombole
Dilila
Bedesa
Godina
Ginchi
Asebot
Mesala
Chacha
Gewane
Dalocha
Chancho
Fulensa
Gelemso
Melkasa
Endibir
Roepeyh
Enewari
Meranga
Rukeyisa
Butajira
Gunchire
Dida Adi
Metehara
Aro Dimtu
Adis Amba
Tulu Bolo
Muke Ture
Haro Kile
Adis Alem
Harawacha
Tarma Ber
Welenchiti
Mucha Roba
Melka Jilo
Debre Sina
Goha Tsion
Debre Tsige
Arba Reketi
Midre Kebda
Bantu Liben
Addis Hiwot
Chefe Donsa
Debre Zeyit
Alem Ketema
Gojo (Jeldu)
Guba Koricha
Asebe Teferi
Shola Gebeya
Debre Birhan
Teferi Birhan
Anchar Bedeyi
Gebre Guracha
Ejere N Shewa
Sire W Hararghe
Arb Gebeya W Shewa
Abomsa (Tinsae Birhan)
Loko
Bofa
Arba
Muger
Eurdo
Koshe
Fetra
Duber
Beltu
Jihur
Sembo
Afdem
Dejen
Ejersa
Boreda
Segele
Kutara
Gebiba
Deneba
Fitale
Mezezo
Jebuha
Adulala
Ankober
Kechemo
Sululta
Ginager
Chifara
Mechara
Berehet
KurkuraDinkiti
Kachisi
Mendida
Tedo Ber
Delajebo
Jima Arsi
Alem Tena
Yemistina
Adami Tulu
Mama Midir
Sirtu Ager
Alem Gebeya
Melka Werer
Biyo Karaba
Tikur Chika
Hagere Sernay
Sheik Hussein
Melka Kunture
41°0'0"E
41°0'0"E
40°0'0"E
40°0'0"E
39°0'0"E
39°0'0"E
38°0'0"E
38°0'0"E
10°0
'0"N
10°0
'0"N
9°0'
0"N
9°0'
0"N
8°0'
0"N
8°0'
0"N
400000
400000
500000
500000
600000
600000
700000
700000
9000
00
9000
00
1000
000
1000
000
1100
000
1100
000
LegendStudy Area
Towns
\ Capital
!5 Regional Capital
!!! Major towns
!! Other towns
Major Rivers
Roads
Trunk
Link
Main Access
Feeder
Collector
New Proposed
Unclassified
0 5025km
´
LOCATION MAP
AbbayAwash
Wabi Shebele Aysha
Genale-Dawa
Tekeze
Omo-Gibe
Denakle
Baro-Akobo
Rift Valley
Mereb
Aysha
OROMIA
SOMALI REGION
AMHARA
AFAR
TIGRAY
SOUTHERN REGIO
50°0'0"E
45°0'0"E
45°0'0"E
40°0'0"E
40°0'0"E
35°0'0"E
35°0'0"E
15°0
'0"N
10°0
'0"N
10°0
'0"N
5°0'
0"N
5°0'
0"N
LegendStudy Area
Region
Major Basin 0 200 400100km
´
Addis Ababa
Project Area
Federal Democratic Republic of Ethiopia
Project Area
i
CONTENTS
Location Map Contents List of Tables List of Figures Abbreviations
Page:
1 Survey Summary ............................................................. 1-1
1.1 Objective and area of the project ................................................................ 1-1
1.2 Methodology of the Project ........................................................................ 1-2
2 Summary of Geography and Geology ............................. 2-1
2.1 Summary of geography .............................................................................. 2-1
2.2 Regional geological and tectonic setting .................................................... 2-4
3 Geology ........................................................................... 3-1
3.1 Adama town, Mt. Boseti and its surrounding areas .................................... 3-1 3.1.1 General ............................................................................................ 3-1 3.1.2 Geological unit ................................................................................ 3-4
3.2 Kone – Mt. Fentale and its surrounding areas .......................................... 3-24 3.2.1 General .......................................................................................... 3-24 3.2.2 Geological unit .............................................................................. 3-26
3.3 Mojo town – Arerti town – Debre Birhan town and its surrounding areas .......................................................................................................... 3-44 3.3.1 General .......................................................................................... 3-44 3.3.2 Geological unit .............................................................................. 3-46
3.4 Awash town – Asebe Teferi town and its surrounding areas ................... 3-61 3.4.1 General .......................................................................................... 3-61 3.4.2 Geological unit .............................................................................. 3-62
3.5 Correlation of stratigraphy of each part of the study area ........................ 3-81
3.6 Correlation of stratigraphy with previous studies ..................................... 3-85
3.7 Geological structure .................................................................................. 3-87 3.7.1 Fault system .................................................................................. 3-87 3.7.2 Active structures ........................................................................... 3-87
3.8 Volcanic activity ....................................................................................... 3-88 3.8.1 Characteristics of volcanic topography in the middle Awash
River basin .................................................................................... 3-88 3.8.2 Volcanic history in the middle Awash River Basin ...................... 3-91
4 Hydrogeology .................................................................. 4-1
ii
4.1 Data collection of hydrogeology ................................................................ 4-1 4.2 Groundwater potential .............................................................................. 4-24
4.2.2 Classification and characteristic of aquifers ................................. 4-29
4.3 Hydrogeological map and groundwater flow ........................................... 4-40
4.4 Water quality testing ................................................................................. 4-44 4.4.1 Results of water quality testing ..................................................... 4-44 4.4.2 Analysis items and methodology .................................................. 4-50 4.4.3 Results of water quality testing ..................................................... 4-51
5 Geology and Hydrogeology around Lake Beseka ........... 5-1
5.1 Topography, geology and geological structure .......................................... 5-1 5.1.1 Topography ..................................................................................... 5-1 5.1.2 Geology ........................................................................................... 5-7 5.1.3 Geological structure ...................................................................... 5-29
5.2 Hydrogeology ........................................................................................... 5-30 5.2.1 Aquifer classification and groundwater flow ................................ 5-30 5.2.2 Hydrogeological map and cross-sections ..................................... 5-38 5.2.3 Results of water quality testing ..................................................... 5-41
iii
List of Tables Page:
Table 1.2.1: Satellite Image for Interpretation .............................................................. 1-3 Table 3.1.1: Stratigraphy in Adama Town-Mt. Boseti .................................................. 3-2 Table 3.1.2: Geological Succession along Adama Town-Mt. Boseti ............................ 3-6 Table 3.1.3: Geological Succession along Lake Koka – Hurita Town – Sire
Town ......................................................................................................... 3-7 Table 3.2.1: Stratigraphy in Kone-Mt. Fentale and its Surrounding Areas ................. 3-25 Table 3.2.2: Geological Succession along Kone-Mt. Fentale ..................................... 3-27 Table 3.2.3: Geological Succession along Mt. Fentale – Awash Town ...................... 3-28 Table 3.3.1: Stratigraphy in Mojo Town-Arerti Town-Debre Birhan Town and
Surrounding Areas .................................................................................. 3-45 Table 3.3.2: Mojo Town-Arerti Town -Debre Birhan Town ...................................... 3-51 Table 3.3.3: Mojo Town – Chefe Donsa Town – Debre Birhan Town ....................... 3-52 Table 3.3.4: Arerti Town – Melka Jiro Town ............................................................. 3-56 Table 3.4.1: Stratigraphy in Awash Town-Asebe Teferi Town .................................. 3-62 Table 3.4.2: Geological Succession of Mieso Town-Asebe Teferi Town-Arba
Bekete Town .......................................................................................... 3-68 Table 3.4.3: Geological Succession of Bordede Town – Bube Town – Belo
Town ....................................................................................................... 3-69 Table 3.4.4: Geological Succession of Adami Hara –Kora Town -Debala Town ...... 3-72 Table 3.4.5: Geological Succession of Asebot Town – Beka Town. .......................... 3-73 Table 3.4.6: Geological Succession of Awash Town – Mieso Town ......................... 3-75 Table 3.5.1: Correlation of stratigraphy in the study area ........................................... 3-82 Table 3.6.1: Correlation of stratigraphy with existing documents and maps .............. 3-86 Table 4.1.1: List of References ...................................................................................... 4-1 Table 4.1.2: Number of Data by Parameter in Well Database (with coordinates) ........ 4-5 Table 4.1.3: Existing Well Data in West Hararge Zone ................................................ 4-8 Table 4.1.4: Existing Well Data Around Lake Beseka ............................................... 4-11 Table 4.1.5: Existing Well Data in Arsi Zone ............................................................. 4-13 Table 4.1.6: Existing Well Data in East Shewa Zone, Amhara Region and others .... 4-16 Table 4.2.1: Aquifer Unit Classification and Characteristics ...................................... 4-29 Table 4.2.2: Modified Hydrogeological Map - Aquifer Classifications and
Definitions .............................................................................................. 4-33 Table 4.2.3: Aquifer Parameters and Units of Existing Wells and JICA Wells .......... 4-34 Table 4.2.4: Aquifer Classification and Productivity .................................................. 4-35 Table 4.2.5: Result of Groundwater Recharge Estimation by Sub-basins .................. 4-36 Table 4.2.6: Ratio between Groundwater Recharge and Yield ................................... 4-39 Table 4.4.1: Sampling List .......................................................................................... 4-46 Table 4.4.2: Previous Water Quality Standard of Ethiopia ......................................... 4-50 Table 4.4.3: New Water Quality Standard of Ethiopia and WHO .............................. 4-51 Table 4.4.4: List of Sampling Points in Dry Season 2015 .......................................... 4-69 Table 5.1.1: Classification and Characteristics of Topography around Lake
Beseka ...................................................................................................... 5-1 Table 5.1.2: Geological stratigraphy around Lake Beseka and correlation with
other areas .............................................................................................. 5-29 Table 5.2.1: Existing Wells and JICA Wells with Columnar Section around Lake
Beseka .................................................................................................... 5-35 Table 5.2.2: Aquifer Unit Classification and Characteristics around Lake Beseka .... 5-37 Table 5.2.3: List of Sampling Points around Lake Beseka ......................................... 5-42
iv
Table 5.2.4: List of Existing Water Quality Data (around Lake Beseka) ................... 5-43 Table 5.2.5: Results and List of Isotope Analysis ....................................................... 5-51 Table 5.2.6: List of Points for Tritium Analysis ......................................................... 5-54
v
List of Figures Page:
Figure 1.1.1: Area Covered by the Geological and Hydrogeological Maps ................. 1-1 Figure 1.2.1: The Project Flow ...................................................................................... 1-2 Figure 1.2.2: SPOT Satellite Image ............................................................................... 1-4 Figure 1.2.3: ALOS Satellite Image .............................................................................. 1-5 Figure 1.2.4: ASTER DEM ........................................................................................... 1-7 Figure 1.2.5: Topographical Information Map by Satellite Images .............................. 1-8 Figure 2.1.1: The Central Sector of the MER ............................................................... 2-1 Figure 2.1.2: Major Basins in Ethiopia ......................................................................... 2-2 Figure 2.1.3: Digital Elevation Model of the Middle Awash River Basin .................... 2-3 Figure 2.1.4: River System of the Middle Awash ......................................................... 2-3 Figure 2.2.1: Schematic Diagram for Development of Red Sea Rift and Aden
Sea Rift, and failed African Rift (MER), (Source: http://www3.interscience.wiley. ............................................................... 2-5
Figure 3.1.1: Location map of outcrops ........................................................................ 3-3 Figure 3.1.2: Kelefa River (L-AB21) ............................................................................ 3-4 Figure 3.1.3: Tulu (L-AB07) (top left), Chefeko (L-AB08)(top light), Mt.Debeso
(L-AB09)(bottom) .................................................................................... 3-5 Figure 3.1.4: Sire (L-AB35) (top), Boko (L-AB11) (bottom) ....................................... 3-8 Figure 3.1.5: Koka Dam (L-AB02) (top), Rukecha (L-MAD40) (bottom) ................... 3-9 Figure 3.1.6: River Robi L-AB28) ......................................................................... 3-10 Figure 3.1.7: Bofa (L-AB25) (top left), Holly Spring (L-AB39) (top right),
Weleso River (L-AB43) (bottom) .......................................................... 3-11 Figure 3.1.8: Photos of Thin Sections of Sample Number140419-1 .......................... 3-12 Figure 3.1.9: Jogo (L-AB06) (top), West of Bofa Town (L-AB22) (bottom) ............. 3-13 Figure 3.1.10: Photos of Thin Sections of Sample Number 140414-1 ....................... 3-14 Figure 3.1.11: Photos of Thin Sections of Sample Number 140414-2 ....................... 3-15 Figure 3.1.12: Photos of Thin Sections of Sample Number 140414-5 ....................... 3-16 Figure 3.1.13: Photos of Thin Sections of Sample Number 140414-6 ....................... 3-17 Figure 3.1.14: Photos of Thin Sections of Sample Number140419-3 ........................ 3-18 Figure 3.1.15: Photos of Thin Sections of Sample Number140419-5 ........................ 3-19 Figure 3.1.16: Northeastern Cliff of Gademsa Caldera (L-AB05) .............................. 3-19 Figure 3.1.17: Boru River (L-AB19) (top), Sire (L-AB37) (bottom) ......................... 3-20 Figure 3.1.18: Gambedra (L-AB38) ............................................................................ 3-21 Figure 3.1.19: Welensu (L-AB17) (left), Mt.Boseti (L-AB29) (right)........................ 3-21 Figure 3.1.20: Madiga, (L-MAD37) (top), Lake Koka (L-AB10) (bottom) ............... 3-22 Figure 3.1.21: Harorecha (L-AB32) (left), Haribona (L-AB42) (right) ...................... 3-23 Figure 3.1.22: Waka Bute (L-AB04) (top), Miesa (L-AB03) (bottom) ...................... 3-24 Figure 3.2.1: Bosena (L-KF02) Bokan ........................................................................ 3-26 Figure 3.2.2: Photos of Thin Sections of Sample Number 140415-4 ......................... 3-29 Figure 3.2.3: Southeastern Foot of Mt. Fentale (L-KF39) .......................................... 3-30 Figure 3.2.4: Sobebor (L-KF23) (top), Boru Alore (L-KF18) (middle) and
Dinbiba (L-KF30) (bottom) ................................................................... 3-31 Figure 3.2.5: Photos of Thin Sections of Sample Number140417-5 .......................... 3-32 Figure 3.2.6: Dodose Use (L-KF20) (top) and Bogda (L-KF25) (bottom) ................. 3-33 Figure 3.2.7: Kone (L-KF13) (top) and Ofe, Southwestern Foot of Kone Caldera
(L-KF03) (bottom) ................................................................................. 3-34 Figure 3.2.8: Photos of Thin Sections of Sample Number 140415-2 ......................... 3-35 Figure 3.2.9: Korke (L-KF10) ..................................................................................... 3-36
vi
Figure 3.2.10: Dinbiba (L-KF31) (top), Southern Foot of Mt. Fentale (L-KF30) (bottom left) and Southern Foot of Mt. Fentale (L-KF34) (bottom right) ....................................................................................................... 3-37
Figure 3.2.11: Photos of Thin Sections of Sample Number 140415-3 ....................... 3-38 Figure 3.2.12: Photos of Thin Sections of Sample Number140417-1 ........................ 3-39 Figure 3.2.13: Photos of Thin Sections of Sample Number140417-2 ........................ 3-40 Figure 3.2.14: Photos of Thin Sections of Sample Number140417-4 ........................ 3-41 Figure 3.2.15: Boru Alore (L-KF21) ........................................................................... 3-42 Figure 3.2.16: Photos of Thin Sections of Sample Number 140415-1 ....................... 3-43 Figure 3.2.17: Dinbiba (L-KF29) ................................................................................ 3-43 Figure 3.3.1: Balchi (L-MAD14) (top), Balchi (L-MAD15) (bottom) ....................... 3-46 Figure 3.3.2: Aroge Minjar (L-MAD29) (top and middle), Chifey (L-MAD12)
(bottom left), Gina Ager (L-MAD30) (bottom right) ............................ 3-48 Figure 3.3.3: Aroge Minjar (L-MAD29) (top), Balchi (L-MAD14) (middle left),
Zengo (L-MAD10) (middle right), Gobemsa (L-MAD25) (bottom) ..... 3-49 Figure 3.3.4: Gidm Asfa (L-MAD21) (top), Zongo (L-MAD10) (bottom left),
Megezeze (L-MAD24) (bottom right) ................................................... 3-50 Figure 3.3.5: Mt. Bokan (L-MAD09) .......................................................................... 3-53 Figure 3.3.6: Samasembet (L-MAD11) ....................................................................... 3-54 Figure 3.3.7: Aroge Minjar (L-MAD29) ..................................................................... 3-54 Figure 3.3.8: Kunche (L-MAD06) .............................................................................. 3-55 Figure 3.3.9: Jolo (L-MAD41) .................................................................................... 3-57 Figure 3.3.10: Chefe Donsa (L-MAD02) .................................................................... 3-58 Figure 3.3.11: Mt. Zikwala (L-MAD41) ..................................................................... 3-58 Figure 3.3.12: Argoba (L-MAD04) (top), Lake Haro Meja (L-MAD01) (bottom
left), Lake Haro Kilole (L-MAD39) (bottom right) ............................... 3-59 Figure 3.3.13: Wubit Ager, Kersa River (L-MAD19) ................................................. 3-60 Figure 3.3.14: Borchota (L-MAD23) .......................................................................... 3-60 Figure 3.3.15: Borchota (L-MAD23) .......................................................................... 3-61 Figure 3.4.1: Arba Rekete (L-AA59) (top), Komena (L-AA35) (bottom left) and
Cheleleka (L-AA09) (bottom right) ....................................................... 3-63 Figure 3.4.2: Huse Ridge (L-AA53) ............................................................................ 3-64 Figure 3.4.3: Photos of Thin Sections of Sample Number140416-1 .......................... 3-65 Figure 3.4.4: Photos of Thin Sections of Sample Number140416-2 .......................... 3-66 Figure 3.4.5: Asebe Teferi (L-AA57) (top), Agemti (L-AA20) (bottom) ................... 3-67 Figure 3.4.6: Gara Gumbi (L-AA06) (top) and Dalecha (L-AA46) (bottom) ............. 3-70 Figure 3.4.7: Type Locality (L-AA30) (top) and its Vicinity (L-AA29) (bottom) ..... 3-71 Figure 3.4.8: Type Locality (L-KF43) (top) and Gara Gumbi Rasa (L-AA10)
(bottom) .................................................................................................. 3-74 Figure 3.4.9: Type Locality, Awash River (L-KF42) (top) and Komena
(L-AA40) (bottom) ................................................................................. 3-76 Figure 3.4.10: Photos of Thin Sections of Sample Number 140416-4 ....................... 3-77 Figure 3.4.11: Type Locality, Riv. Jejeba (L-AA03) .................................................. 3-78 Figure 3.4.12: Type Locality, Adami Hara (L-AA33) (top), Buri Korkoda Ridge
(L-AA22) (bottom left) and Awash Arba (L-KF40) (bottom right) ...... 3-79 Figure 3.4.13: Type Locality, Mt. Asebot (L-AA44) (top), Kulbas (L-AA38)
(bottom left) and Aneno (L-AA21) (bottom right) ................................ 3-80 Figure 3.4.14: Awash River (L-KF41) ........................................................................ 3-81 Figure 3.5.1: Geological Map of Study Area .............................................................. 3-83 Figure 3.5.2: Geological Cross-Section of Study Area ............................................... 3-84
vii
Figure 3.7.1: “En Echelon” arrangement of the active volcano-tectonic axis within the northern part of the Ethiopian rift (after Elc Electroconsult and Geotermica Italiana, 1987) ...................................... 3-88
Figure 3.8.1: Elevation Map of the Study Area ........................................................... 3-90 Figure 3.8.2: Stages in the Development of the Ethiopian Rift (after Kazmin and
Berhe, 1978) ........................................................................................... 3-91 Figure 4.1.1: Location Map of Existing Wells .............................................................. 4-6 Figure 4.1.2: Yield of Existing Wells ............................................................................ 4-7 Figure 4.1.3: Yield and Drilling Depth in West Hararge Zone ................................... 4-10 Figure 4.1.4: Yield and Drilling Depth in Arsi Zone .................................................. 4-15 Figure 4.1.5: Yield and Drilling Depth in East Shewa Zone, Amhara Region and
others ...................................................................................................... 4-21 Figure 4.1.6: Location Map of Spring and Hand Dug Wells ...................................... 4-23 Figure 4.2.1: Relation between Yield and Depth of the Existing Wells ..................... 4-25 Figure 4.2.2: Groundwater Level Contour Map in West Hararge Area ...................... 4-26 Figure 4.2.3: Groundwater Level Contour Map in Amhara Area ............................... 4-27 Figure 4.2.4: Groundwater Level Contour Map in East of Lake Koka to Dera
Town ....................................................................................................... 4-28 Figure 4.2.5: Groundwater Level Contour Map in North to East of Lake Koka ......... 4-28 Figure 4.2.6: Groundwater Level Contour Map around Lake Beseka ........................ 4-29 Figure 4.2.7: Location Map of Sub-Basin, Small Towns and Model Existing
Wells ....................................................................................................... 4-38 Figure 4.3.1: Hydrogeological Map in the Middle Awash River Basin ...................... 4-41 Figure 4.3.2: Hydrogeological Cross Sections ............................................................ 4-42 Figure 4.3.3: Groundwater Table Contour Map .......................................................... 4-43 Figure 4.4.1: Location Map of Sampling Points for Water Quality Testing ............... 4-45 Figure 4.4.2: Trilinear diagram ................................................................................... 4-53 Figure 4.4.3: Trilinear Diagram (All Data) ................................................................. 4-55 Figure 4.4.4: Trilinear Diagram (River Water) ........................................................... 4-56 Figure 4.4.5: Trilinear Diagram (Wells) ...................................................................... 4-57 Figure 4.4.6: Trilinear Diagram (Spring) .................................................................... 4-58 Figure 4.4.7: Trilinear Diagram (Lake Water) ............................................................ 4-59 Figure 4.4.8: Trilinear Diagram (Others) .................................................................... 4-60 Figure 4.4.9: Hexadiagram .......................................................................................... 4-61 Figure 4.4.10: Distribution Map of Hexadiagram (All data: Data around Lake
Beseka at upper left) ............................................................................... 4-63 Figure 4.4.11: Distribution Map of Hexadiagram (River water) ................................. 4-64 Figure 4.4.12: Distribution Map of Hexadiagram (Wells) .......................................... 4-65 Figure 4.4.13: Distribution Map of Hexadiagram (Spring) ......................................... 4-66 Figure 4.4.14: Distribution Map of Hexadiagram (Lake Water) ................................. 4-67 Figure 4.4.15: Distribution Map of Hexadiagram (Others) ......................................... 4-68 Figure 4.4.16: Location Map of Sampling Points along Awash River (Short
Rainy and Dry Seasons) ......................................................................... 4-70 Figure 4.4.17: The Hexa diagram of Short Rainy and Dry Season along Awash
River ....................................................................................................... 4-70 Figure 4.4.18: Trilinear diagram of Short Rainy and Dry Season along Awash
River ....................................................................................................... 4-71 Figure 5.1.1: Elevation Map around Lake Beseka ........................................................ 5-3 Figure 5.1.2: Topographic Classification Map around Lake Beseka (background:
shaded relief map created from ASTER DEM data) ................................ 5-4
viii
Figure 5.1.3: NW-SE Topographic Section around Lake Beseka (A-A’) ..................... 5-5 Figure 5.1.4: E-W Topographic Section around Lake Beseka (B-B’) .......................... 5-5 Figure 5.1.5: N-S Topographic Section around Lake Beseka (C-C’) ........................... 5-6 Figure 5.1.6: Index map of aerial photos used for the topographical analysis .............. 5-6 Figure 5.1.7: Paleo-channel flowing into the southern part of Lake Beseka................. 5-7 Figure 5.1.8: Geological Map around Lake Beseka ...................................................... 5-8 Figure 5.1.9: Geological section around Lake Beseka .................................................. 5-9 Figure 5.1.10: Outcrop photos of Birenti-Hada rhyolites ............................................ 5-10 Figure 5.1.11: Outcrop photos of the older ignimbrite ................................................ 5-11 Figure 5.1.12: Outcrop photos of the Nura Hira basalts .............................................. 5-12 Figure 5.1.13: Outcrop photo of Dino ignimbrite ....................................................... 5-12 Figure 5.1.14: Outcrop photos of Sobebor volcanic sand beds ................................... 5-13 Figure 5.1.15: Outcrop photos of the Pleistocene basalts............................................ 5-15 Figure 5.1.16: Outcrop photo of Kone ignimbrite ....................................................... 5-16 Figure 5.1.17: Outcrop photos of the Fentale volcanic rocks ...................................... 5-17 Figure 5.1.18: Outcrop photos of the Fentale ignimbrite ............................................ 5-18 Figure 5.1.19: Outcrop photos of the blisters of the Fentale ignimbrite ..................... 5-19 Figure 5.1.20: Outcrop photos of the recent basalts .................................................... 5-20 Figure 5.1.21: Photos of alluvial plains and deposits .................................................. 5-20 Figure 5.1.22: Location of existing wells and observation wells constructed by
this project and profile lines around Lake Beseka ................................. 5-22 Figure 5.1.23: Borehole log profile A-A’ section ....................................................... 5-23 Figure 5.1.24: Borehole log profile B-B’ section ........................................................ 5-24 Figure 5.1.25: Borehole log profile C-C’ section ........................................................ 5-25 Figure 5.1.26: Borehole log profile D-D’ section ....................................................... 5-26 Figure 5.1.27: Borehole log profile E-E’ section ........................................................ 5-27 Figure 5.1.28: Borehole log profile F-F’ section ......................................................... 5-28 Figure 5.1.29: Outcrop photos of faults distributed in the detailed study area ........... 5-30 Figure 5.2.1: Geological Map, Existing Wells and JICA Wells around Lake
Beseka .................................................................................................... 5-32 Figure 5.2.2: Columnar Section of JICA Well (AW BH-3) and Geological
Correlation .............................................................................................. 5-33 Figure 5.2.3: Columnar Section of JICA Well (AW BH-4N) and Geological
Correlation .............................................................................................. 5-33 Figure 5.2.4: Columnar Section of JICA Well (AW BH-5) and Geological
Correlation .............................................................................................. 5-34 Figure 5.2.5: Groundwater Level Contour Map around Lake Beseka (Less than
100 m depth of Existing Wells) .............................................................. 5-36 Figure 5.2.6: Groundwater Level Contour Map around Lake Beseka (More than
100 m depth of Existing Wells) .............................................................. 5-36 Figure 5.2.7: Well Depth and Fluoride Concentration around Lake Beseka .............. 5-38 Figure 5.2.8: Hydrogeological Map around Lake Beseka ........................................... 5-39 Figure 5.2.9: Hydrogeological Section around Lake Beseka ...................................... 5-40 Figure 5.2.10: Location Map of Water Quality Testing Points around Lake
Beseka .................................................................................................... 5-43 Figure 5.2.11: Trilinear Diagram around Lake Beseka ............................................... 5-45 Figure 5.2.12: Hexadiagram at Sampling Points around Lake Beseka ....................... 5-46 Figure 5.2.13: Hexadiagram of Main Sampling Points at West of Lake Beseka ........ 5-47 Figure 5.2.14: Hexadiagram of Main Sampling Points at South West of Lake
Beseka .................................................................................................... 5-48
ix
Figure 5.2.15: Hexadiagram of Main Sampling Points at South of Lake Beseka ....... 5-49 Figure 5.2.16: Delta Diagram of Stable Isotope around Lake Beseka ........................ 5-53
x
Abbreviations
AAU Addis Ababa University AGRAP Alidge Groundwater Resources Assessment Project AIDS Acquired Immune Deficiency Syndrome ALOS Advanced Land Observing Satellite ASTER Advanced Spaceborne Thermal Emission and Reflection Radiometer ASTER-GDEM ASTER-Global Digital Elevation Model BFI Base Flow Index CAD Computer Aided Design (System) CDE Center for Development and Environment, Ministry of Agriculture CFC Chloride Fluoride Carbon CREC China Railway Engineering Corporation CSA Central Statistical Agency CSE The Conservation Strategy of Ethiopia C/P Counterpart (organization or personnel) DB Datebase DCI Ductile Cast Iron DEM Digital Elevation Model DF/R Draft Final Report DTH Down-the-hole Hammer DWL Dynamic Water Level EA Environmental Assessment EC Electric Conductivity EEPCO Ethiopia Electric Power Corporation EGRAP Ethiopian Groundwater Resources Assessment Program EIA Environmental Impact Assessment EIGS Ethiopian Institute of Geological Survey, now renamed as Geological Survey of
Ethiopia (GSE) EL Elevation ELC Elc electroconsult milano and Geotermica italiana pisa, Italia (an Italian
Consultant) ELSA Equilibrium Lake Surface Area EMA Ethiopia Mapping Agency ENGDA Ethiopian National Groundwater Database ENGWIS Ethiopian National Groundwater Information System EPA Environmental Protection Agency, now renamed as Ministry of Environment
and Forest (MEF) EPC Environmental Protection Council ERA Ethiopian Road Authority ERC Ethiopian Railway Corporation ESA Ethiopian Standard Agency ESIA Environmental and Social Impact Assessment ET Evapotranspiration EWCA Ethiopian Wildlife Conservation Authority EWTEC Ethiopia Water Technology Center, now renamed as Ethiopia Water
Technology Institute (EWTI) EWTI Ethiopia Water Technology Institute, formerly known as Ethiopia Water
Technology Center (EWTEC) F/R Final Report FAO Food and Agriculture Organization of the United Nations FAO-AGLW FAO Water Resource, Development and Management Services
xi
FDM Finite Difference Method FEM Finite Element Method GD Groundwater Directorate (of MoWIE) GDP Gross Domestic Product GHB General Head Boundary GIS Geographical Information System GL Ground Level GNI Gross National Income GPS Global Positioning System GSE Geological Survey of Ethiopia GSP Galvanized Steel Pipe GTP Growth and Transformation Plan GWR Groundwater Recharge HIV Human Immunodeficiency Virus IAEA International Atomic Energy Agency IC/R Inception Report IEE Initial Environmental Examination IMF International Monetary Fund INGEIS Instituto de Geocronología y Geología Isotópica (Institute of Geochronology
and Geology, Argentine) ISO International Standard Organization ISODATA The Iterative Self-Organizing Data Analysis Technique IT/R Interim Report ITCZ Inter-tropical Convergence Zone JICA Japan International Cooperation Agency LEL Local Evaporation Line LMWL Local Meteoric Water Line M&E Monitoring and Evaluation M/M Minutes of Meeting MCM Million Cubic Meter MDGs Millennium Development Goals MEF Ministry of Environment and Forest, formerly known as Environmental
Protection Agency (EPA) MER Main Ethiopian Rift MOA Ministry of Agriculture MoWR Ministry of Water Resources, now renamed as Ministry of Water, Irrigation and
Electricity (MoWIE) MoWE Ministry of Water and Energy, now renamed as Ministry of Water, Irrigation
and Electricity (MoWIE) MoWIE Ministry of Water, Irrigation and Electricity, formerly known as Ministry of
Water, Irrigation and Energy(MoWIE), Ministry of Water and Energy (MoWE) or Ministry of Water Resources (MoWR)
MSE Metehara Sugar Estate MWL Meteoric Water Line NASA National Aeronautics and Space Administration, USA NGI National Groundwater Institute NGO Non-Governmental Organization NMA National Meteorology Agency OLEPB Oromia Land and Environmental Protection Bureau ORP Oxidation and Reduction Potential O(R)WMEB Oromia (Regional) Water, Material and Energy Development Bureau OWNP One WASH National Program OWWDSE Oromia Water Works Design and Supervision Enterprise
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P/R Progress Report PA Preliminary (Environmental) Assessment PASDEP Plan for Accelerated and Sustained Development to End Poverty PC Personal Computer PPP Purchasing Power Parity PRSP Poverty Reduction Strategy Paper PVC Polyvinyl Chloride R/D Record of Discussions REA Regional Environmental Agencies RESTEC Remote Sensing Technology Center of Japan RVLB Rift Valley Lakes Basin SC Steering Committee SCM Steering Committee Member or Steering Committee Meeting SDPRP Sustainable Development and Poverty Reduction Program SEA Strategic Environmental Assessment SFGS Streamflow Gauging Station SP Spontaneous potential SPOT Satellite Pour l'Observation de la Terre (French Satellite for Earth Observation) SRTM Shuttle Radar Topography Mission SS Suspended Solids TDS Total Dissolved Solids TEM Transient (or Time-domain) Electromagnetic Method TIR Thermal Infrared TM Thematic Mapper TOR Terms of Reference TU Tritium Unit TWSSO Town Water Supply Service Office TWSSSE Town Water Supply and Sewerage Service Enterprise UAP Universal Access Program UNEP United Nations Environment Programme UNESCO United Nations Educational, Scientific and Cultural Organization UNICEF United Nations Children’s Fund uPVC Unplasticized Polyvinyl Chloride USBR United States Bureau of Reclamation USGS United States Geological Survey UTM Universal Transversal Mercator VES Vertical Electrical Sounding VIP Ventilation Improved Pit WASH Water Supply, Sanitation and Hygiene Program WB World Bank WC Water Committee WFB Wonji Fault Belt WHO World Health Organization WSDP Water Sector Development Program WSSM Water Supply and Sanitation Master Plan WWDSE Water Works Design and Supervision Enterprise WWMEO Woreda Water, Mineral and Energy Office ZWMEO Zonal Water, Mineral and Energy Office
Chapter 1
Survey Summary
The Project for Groundwater Resources Assessment JICA in the Middle Awash River Basin, Final Report (Geological/Hydrogeological Maps) KOKUSAI KOGYO CO., LTD.
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1 Survey Summary
1.1 Objective and area of the project a. Objective of the project
The geological and hydrogeological study was executed as a part of the Project of “Groundwater Resources Assessment in the Middle Awash River Basin in the Federal Democratic Republic of Ethiopia (hereafter, the Project)” based on the results of the record of discussions (R/D) agreed and signed by the Federal Democratic Republic of Ethiopia and Japan International Cooperation Agency (JICA) on 27 May 2013. The objective of this geological and hydrogeological study is to create the geological map and hydrogeological map in the Middle Awash River Basin based on the results of the analysis of geology, hydrogeology, and water quality and to discuss the groundwater potential through the use of the geological and hydrogeological map.
b. The Project schedule
The Project started in May 2013 and was confirmed to end in December 2015.
c. Area of the Project
The area of approximately 20,000km2 in the Middle Awash River Basin covered by the geological and hydrogeological maps is shown in Figure 1.1.1 below;
Figure 1.1.1: Area Covered by the Geological and Hydrogeological Maps
Source: the Project Team, Data: Production by Project member
The Project for Groundwater Resources Assessment JICA in the Middle Awash River Basin, Final Report (Geological/Hydrogeological Maps) KOKUSAI KOGYO CO., LTD.
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1.2 Methodology of the Project a. The Project flow
The Project flow was shown in the following Figure 1.2.1; The geological and hydrogeological maps were created mainly by five works, namely satellite image analysis (for example land classification, lineament analysis), classification of geological units based on the existing geological maps and reports, geological field survey, arrangement of existing well data, and evaluation of hydrogeological units.
Figure 1.2.1: The Project Flow
Source: the Project Team, Data: Production by Project member
The Project for Groundwater Resources Assessment JICA in the Middle Awash River Basin, Final Report (Geological/Hydrogeological Maps) KOKUSAI KOGYO CO., LTD.
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b. Satellite image analysis
b.1 Satellite image
The interpretation of surface information on satellite imagery to grasp the volcanic geographical condition and geological structure for the basic data of hydrogeological condition was conducted using the following satellite imagery (refer to Table 1.2.1).
Table 1.2.1: Satellite Image for Interpretation
Satellites Shooting data and information Main purpose
1994-, resolution, 30m Extract DEM to create contours
2006-2007, Pacromatic, 0.5m resolution
high accuracy , Lineament, Geological structure, Topography, Vegetation, Collection of land use information
2006, 3 bands, ortho-rectified Extract DEM, Interpretation on 3D model
2008-2011,resolution, 10m Elevation map, Hydrology information map, Wide-area topography, vegetation, Collection of land use information
ALOS: Purchasing area for the shooting and shooting data
The SOPT and ALOS satellite imagery have been shown in Figure 1.2.2 and Figure 1.2.3.
The Project for Groundwater Resources Assessment JICA in the Middle Awash River Basin, Final Report (Geological/Hydrogeological Maps) KOKUSAI KOGYO CO., LTD.
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Figure 1.2.2: SPOT Satellite Image
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MelkaWerer
SirtuAger
Delajebo
MelkaKunture
DinkitiSheikHussein
AlemGebeya
HagereSernay
Sembo
Deneba
Berehet
Gebiba
AlemTena
Mechara
Chifara
Ginager
Duber
Sululta Arba
Bofa
Koshe
Segele
KechemoJimaArsi
Ankober
Eurdo
Adulala
Bulbula
AdamiTulu
Wilbarey
Muger
DebreZeyit
DebreBirhan
FicheGebreGuracha
Chacha
Asebot
Sheno
SholaGebeya
Ambo
Ginchi
TejiGodina
ChefeDonsa
MelkaJilo Metehara Bedesa
Sire WHararghe
AncharBedeyi
AddisHiwot
Abomsa(TinsaeBirhan)
ModjoBantuLibenDilila
Bu-i MidreKebda
Ombole
Koshim
TibilaTeferiBirhan
Magna
Hujufa
BeleArsi
HobeRobi
Roepeyh
Ziway
HurutaEndibir
Bube
Woliso
AdisAlem
AsebeTeferi
Asela
HaroKile
Kula
Dera
Kibet
Meki
MukeTure
Dida Adi
Merewa
Sodoma
TuluBolo
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Arara
AgemtiIteya
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Chancho
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Gola
Welenchiti
Rukeyisa
Arerti
Diksis
SagureDalocha
Wanje
DebreTsige
Nazret
AddisAbeba
Omo-Gibe
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The Project for Groundwater Resources Assessment JICA in the Middle Awash River Basin, Final Report (Geological/Hydrogeological Maps) KOKUSAI KOGYO CO., LTD.
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Figure 1.2.3: ALOS Satellite Image
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AddisHiwot Abomsa
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Koshim
Tibila
TeferiBirhan
Magna
Huruta
Dera
Guna
GubaKoricha
Melkasa
Mine
Iteya
Welenchiti
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KachisiFitale
MelkaWerer
SirtuAger
Delajebo
MelkaKunture
DinkitiSheikHussein
AlemGebeya
HagereSernay
Sembo
Deneba
Berehet
Gebiba
AlemTena
Mechara
Chifara
Ginager
Duber
Sululta Arba
Bofa
Koshe
Segele
KechemoJimaArsi
Ankober
Eurdo
Adulala
Bulbula
AdamiTulu
Wilbarey
Muger
DebreZeyit
DebreBirhan
FicheGebreGuracha
Chacha
Asebot
Sheno
SholaGebeya
Ambo
Ginchi
TejiGodina
ChefeDonsa
MelkaJilo Metehara Bedesa
Sire WHararghe
AncharBedeyi
AddisHiwot
Abomsa(TinsaeBirhan)
ModjoBantuLibenDilila
Bu-i MidreKebda
Ombole
Koshim
TibilaTeferiBirhan
Magna
Hujufa
BeleArsi
HobeRobi
Roepeyh
Ziway
HurutaEndibir
Bube
Woliso
AdisAlem
AsebeTeferi
Asela
HaroKile
Kula
Dera
Kibet
Meki
MukeTure
Dida Adi
Merewa
Sodoma
TuluBolo
Arb GebeyaW Shewa
Guna
Gunchire
GubaKoricha
Melkasa
Mine
Suten
Arara
AgemtiIteya
Gelemso
Chole
Butajira
Chancho
Akaki
Lemi
Gojo(Jeldu)
Gola
Welenchiti
Rukeyisa
Arerti
Diksis
SagureDalocha
Wanje
DebreTsige
Nazret
AddisAbeba
Omo-Gibe
Awash
Abbay
RiftValley
WabiShebele
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The Project for Groundwater Resources Assessment JICA in the Middle Awash River Basin, Final Report (Geological/Hydrogeological Maps) KOKUSAI KOGYO CO., LTD.
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c. Surface interpretation
The Digital Elevation Model (DEM) has been generated from the SRTM for shaded relief model and Aster Satellite imagery (refer to Figure 1.2.4). The data has been applied to create contours and shaded relief model to understand the surface characteristics of the Study area. The shaded relief model has been utilized to assess the lineaments and other geomorphological marks (such as volcanic craters and bodies) to support the structural evidence in relation to its geological setting and history. The major faults, lineaments and volcanic topographic aspects are presented in Figure 1.2.5 for using the shaded relief model, SPOT and ALOS imageries.
The geological structures in this area are characterized by the MER distributed from Rift Valley Lakes Basin (hereafter refer to as “RVLB”) and the Southern Afar Rift lied next to the northeast of the MER. The MER extends from the southern Afar margin to the Lake Chamo area in RVLB, whereas the South-western Ethiopian Rift (hereafter refer to as “SWR”) is located to the west and represents roughly N-S trending basins related to the Kenya Rift. The Gregory rift of Kenya links to the north with Chew Bahir rift. In accordance with Halcrow 2008, the character of the faults in the two rifts is explained
In a large sense, the central MER direction has been changed from NNE-SSW in the southwest Study area to NE-SW in the main Study area, and the western and eastern rift escarpment run in NE-SW direction (refer to Figure 1.2.5).
This area is called as northern MER, and the northern MER continues to run to the south Afar Rift in NE-NNE direction. The east rift escarpment come to the rift floor as the step faults in the east rift of the Study area, but the west escarpment is unclear. The rift floors, plain area bounded by the both side escarpment, lie in the grabens from the northern part of RVLB to the northeast of the Study area. The scablands have distributed continuously in the rift floor, and runs to the south Afar Rift. These volcanic bodies have lined from the Corbetti, Aluto volcanos (the Aluto is active volcano) in the central MER of RVLB to the Tullu Move, Gedemsa, Boset, Kone and Fantale volcanoes in NE-SW direction in the eastern MER, and have accompanied with caldera and rhyolitic pyroclastic flows largely. There are lots of scoria pyroclastic cones in surrounding volcanic lines. The floor of northern MER is dissected by clear, fresh NE-SW to NNE-SSE trending faults known as the WFB, and WFB can be traced to the southern Afar Rift.
The Project for Groundwater Resources Assessment JICA in the Middle Awash River Basin, Final Report (Geological/Hydrogeological Maps) KOKUSAI KOGYO CO., LTD.
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Figure 1.2.4: ASTER DEM
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DelajeboMelka
Kunture
Alga
Sedika
Dinkiti SheikHussein
HaderoTunto
BurkaJere
Kobo(Harar)
MamaMidir
AlemGebeya
Kurkura
HagereSernay
SemboHareto
Deneba
Jihur
Siba
Yemistina
Yeweynit
SireGino
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Saja
AlemTena
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Dole
Ginager
Kutara
Duber
Fetra
Sululta
Delo
Arba
Kulubi
Bofa
Koshe
Gena
Segele
Boreda
Nefera
Taza
Kechemo
Gamoji
JimaArsi
GoroBale
Loko
Ejersa
Ankober
Eurdo
Adulala
Banta
Bulbula
AdamiTulu
Wilbarey
Deneba
Baso
Kose
Omonada
Dinkore
Muger
AlemKetema
DebreZeyit
GohaTsion Robit
TarmaBer
DebreSina
DebreBirhan
EnewariEjere NShewa
FicheGebre
Guracha
Fincha-aChacha Bike
GotaErer
BedenoHarawacha
Doba
Mesala
Asebot
Sheno
SholaGebeyaGoben
Sheboka
HamusGebeya WShewa
Guder AmboGinchi
Teji Godina
ChefeDonsa
MelkaJilo Metehara Bedesa
Sire WHararghe
Harew
MuchaRoba
Tirtira
HmeroAncharBedeyi
AddisHiwot
Abomsa(TinsaeBirhan)
ModjoBantuLibenDilila
SilkAmba
Alem GenaW Shewa
BotorKetar
ToleJima Abelti
WelkiteBu-i
MidreKebda
Ombole
Koshim
Tibila TeferiBirhan
Magna
Hujufa
BeleArsi
Hobe
Gobesa
Robi
Meliyu
HisuSinana
Goba
Agarfa
Mio
KoreArsi
Kofele
Shashemene
ArekaWaka
LomaBale Zima
Sodo
OfaBoditiAbelaLida Selka Sof Umar
AlidiAdejijo
Tibe
Robe
Roepeyh
Ziway
Timbite
Tiro
Hunte
HurutaEndibir
Ejaji
Bube
Woliso
Ramis
HajoAfati
Shinshicho
AdisAlem
Goda
Rago
Asasa
AsebeTeferi
Asela
HaroKile
Haydro
Kula
Shambu
Dera
Deder
Burka
ArsiNegele
KersaChilalo
Kibet
Meki
MukeTure
Shone
Dida Adi
Yejube
Merewa
Sodoma
TuluBolo
Arb GebeyaW Shewa
Farichu
Guna
Gunchire
MumichaGubaKoricha
Miaw
Mazorya
Dodola
Abebe
Hosaina
AlemGena EShewa
Melkasa
Mine
Molale
Morocho
Morsito
Mana
Ada-a
Niso
Obo
Sura
Suten
GurandaArsi
Gurlero
Arara
ArbaReketi
Guracha
AgemtiIteya
Boko
Gelemso
Chofira
Chole
Fonko
FulensaTawla
Butajira
Chancho
Akaki
Lemi
WeyabetaWeyge
AbdelaBale
AdisAmba
Durame
Edeneba
Gojo(Jeldu)
Gola
Welenchiti
Rukeyisa
Yilu
Arerti
AroDimtu
Bele
Giyorgis
Aje
Diksis
Sagure
Sirba
Dalocha WanjeFofa
Gibe Asendabo
GimbichuDoyoGena Alaba
Kulito
Aweli
Gedeb
GunaArsi
Jara
Ginir
Hirna
Adaba
DebreTsige
Nazret
Awasa
AddisAbeba
Omo-Gibe
Awash
Abbay
Genale-Dawa
RiftValley
WabiShebele
LakeErtele
LakeDendi Lake Ala
Semite
LakeAbijata
LakeShalla
Lake AwassaLake O'ACheleleku
LakeGoletsho
LakeChomen
LakeKoka
LakeLangano
LakeZiway
Lake Dalay
LakeWenchi
LakeBeseka
41°0'0"E
41°0'0"E
40°0'0"E
40°0'0"E
39°0'0"E
39°0'0"E
38°0'0"E
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0"N
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Source: the Project Team, Data: ASTER
The Project for Groundwater Resources Assessment JICA in the Middle Awash River Basin, Final Report (Geological/Hydrogeological Maps) KOKUSAI KOGYO CO., LTD.
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Figure 1.2.5: Topographical Information Map by Satellite Images
(m)
(m)
Source: the Project Team, Data: SRTM+ Result of survey in this project
The Project for Groundwater Resources Assessment JICA in the Middle Awash River Basin, Final Report (Geological/Hydrogeological Maps) KOKUSAI KOGYO CO., LTD.
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d. Creating of the geological map
The main existing geological maps in the Project area and its surrounding areas are as follows;
Geological map of Nazret, Ethiopian Institute of Geological Surveys (EIGS), 1978 Geology and Developing of the Nazret area, northern Ethiopia rift, Kazmin etc. EIGS
1978 Geological map of Dire Dawa, EIGS, 1985 Geological map of Debre Birhan, Geological Survey of Ethiopia (GSE), 1993 Geology of Debre Birhan area, Daniel Mesheha etc. compiled, GSE, 2010 Geological map of Akaki Beseka area, GSE, 1997 Geology of Akaki Beseka, Efrem Beshawered compiled, GSE, 2010 Geology of Addis Ababa map sheet, GSE, 1997 Geology of Addis Ababa city, Getahun assigned, GSE, 2007
A reliable hydrogeological map was created based on a detailed geological map. Therefore, in the preliminary survey of geology in the field, the middle Awash River Basin was divided into four areas in accordance with the aspects of geology and distribution. The strata of each area were correlated based on the specific geology (a key bed), and the correlation chart was described. Finally, the stratigraphy in the entire area was created and the geological map was completed in the middle Awash River Basin (Map scale of 1:250,000 in the entire area and 1:100,000 in Lake Beseka area).
Chapter 2
Summary of Geography and Geology
The Project for Groundwater Resources Assessment JICA in the Middle Awash River Basin, Final Report (Geological/Hydrogeological Maps) KOKUSAI KOGYO CO., LTD.
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2 Summary of Geography and Geology
2.1 Summary of geography a. Landform
The Study area is located in the northern sector of the Main Ethiopian Rift (hereafter referred to as “MER”), and the Study area of the northeast broadens northward into the Afar Rift (refer to Figure 2.1.1: : Northern; : Central and : Southern of MER respectively). The geological tectonic direction in the rift escarpment of MER has been changed from NE-SW to ENE-WSW between and (refer to Figure 2.1.1), and it made an aperture at the Aden junction in the Afar Rift.
The Study area is bounded by the western rift escarpment along the northwest highlands heading towards Addis Ababa, and the altitude of the highlands ranges from 1500m to 2600m above mean sea level (hereafter refer to as “amsl”). The graben in MER runs in NE-SW direction. The altitude of the lowlands in the Study area changes from 1750m amsl of Tuluri Mountain in the southeast, to 1000m amsl at Awash area in the east. The rift floors are subjected to recent volcanic activities from Moye volcano (altitude 2349m amsl) in the southwest, to Fantale volcano (altitude 2007m amsl) in the east. In between of the two volcanoes, several volcanoes and pyroclastic cones are distributed continuously. In Arsi zone, located in south and southwest in the Study area, the rift escarpment is located between the central rift of MER to the west and the Arsi plateau to the east. The altitude of this escarpment ranges from 1500m amsl to 2500m amsl. The Arsi plateau bounded by the lowland in the east and the altitude of the lowland changes from 1000m to 1900m amsl. The Arsi plateau elevation ranges from 2000m amsl at Sire to 3625m amsl at Arba Gugu Mountain.
Figure 2.1.1: The Central Sector of the MER
b. Watershed classification
In Ethiopia, there are 12 major basins and each is subdivided into minor sub-basins (divided by the Ministry of Water Resources (hereafter refer to as “MoWR”) (old name) refer to Figure 2.1.2). The Study area lies next to the northeast of Rift Valley Lakes Basin and the topographical elevation decreases toward the northeast in general. The Awash River flows
Source: G. Woldegabriel, 1990
The Project for Groundwater Resources Assessment JICA in the Middle Awash River Basin, Final Report (Geological/Hydrogeological Maps) KOKUSAI KOGYO CO., LTD.
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toward the northeast, in which direction the elevation of topography also decreases, and its flow direction changes to the north in its middle area.
Source: Ministry of Water, Irrigation and Electricity: MoWIE
Figure 2.1.2: Major Basins in Ethiopia
c. Hydrographic system
The Awash River source is Mt. Warque in the west of Addis Ababa. The river runs toward south-eastern direction for around 130 km and then changes its direction to the northeast at around Mt. Zuqualla. After passing through the Awash National Park, the Awash River is being joined by the Kesem River, the biggest tributary, from its left bank side. The river finally flows into Lake Abbe located on the national boundary with Djibouti. Since Lake Abbe has no water outfall, the Awash River Basin forms a closed water area. The total length of the Awash River is 1,200 km and the total catchment area is 112,700 km2.
The Middle Awash River Basin is defined by the Ministry of Water, Irrigation and Energy (MoWIE) as the watershed area upstream Melka Werer town in Afar Region. Total catchment area of the Middle Awash is 29,280 km2 according to the measurement by the JICA Study Team with available Digital Elevation Models (DEMs). The length of the Middle Awash reaches around 380 km.
General topographic view and river system of the Middle Awash River Basin are shown in Figure 2.1.3 and Figure 2.1.4, respectively.
MEREB GASH
TEKEZE
ABBAY
AWASH
DENAKIL
BARO AKOBO
OMO GIBE
AYSH
WABI SHEBELE
OGADEN
GENALE DAWA
RIFT VALLY
Ministry of Water Recourses Water Recourses information,
Natural Recourses & Environmental Meta data Center
GIS & Remote Sensing Group
Major River Other Rivers
Fresh Water Safety Lakes Sandy Salt Plain
International Border
River Basins Border
The Project for Groundwater Resources Assessment JICA in the Middle Awash River Basin, Final Report (Geological/Hydrogeological Maps) KOKUSAI KOGYO CO., LTD.
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Figure 2.1.3: Digital Elevation Model of the Middle Awash River Basin
Figure 2.1.4: River System of the Middle Awash
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Addis Abeba
Adama (Nazret)
Gola
Mine
Guna
Meki
Dera
Kula
Bube
RobiHobe
Bu-i
Teji
Wanje
Akaki
Chole
Iteya
Suten
Kibet
AselaZiway
Magna
Modjo
Sheno
Diksis
Arerti
Agemti
Sodoma
Merewa
Woliso
Huruta
HujufaTibila
Koshim
Dilila
BedesaGodina
Ginchi
Asebot
Chacha
Chancho
Gelemso
Melkasa
Endibir
RoepeyhHombole
Butajira Dida Adi
Metehara
Tulu Bolo
Muke Ture
Haro Kile
Adis Alem
Welenchiti
Melka Jilo
Debre Tsige
Midre Kebda
Bantu Liben
Addis Hiwot
Chefe Donsa
Gojo (Jeldu)
Guba Koricha
Shola Gebeya
Debre Birhan
Teferi Birhan
Anchar Bedeyi
Arb Gebeya W Shewa
Abomsa (Tinsae Birhan)
Bishoftu (Debre Zeyit)
Bofa
Arba
Muger
Koshe
Duber Sembo Segele
Deneba
Fitale
Adulala
Ankober
Kechemo
Sululta
Ginager
Chifara
Mechara
Berehet
Mendida
Delajebo
Jima Arsi
Alem Tena
Adami Tulu
Sirtu Ager
Alem Gebeya
Melka Werer
Hagere Sernay
Melka Kunture
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38°0'0"E
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Elevation (m. amsl)
Source: the Project Team, Data: Result of survey in this Project
Source: the Project Team, Data: Result of survey in this Project
The Project for Groundwater Resources Assessment JICA in the Middle Awash River Basin, Final Report (Geological/Hydrogeological Maps) KOKUSAI KOGYO CO., LTD.
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2.2 Regional geological and tectonic setting a. Regional geological setting
The study area belongs to northern part of the Main Ethiopian Rift (MER). MER developed over a span from the Oligocene to the Quaternary. During that period, major volcanic episodes are recognized in Oligocene, middle Miocene, late Miocene, early-middle Pleistocene and Holocene (WoldeGabriel et al. 1990). An overview of the history of MER development is as follows;
The oldest volcanic activities are basalt and rhyolite flows in Oligocene, exposed in and around the rift margins (e.g. Blue Nile gorge), which formed lava plateau in the surrounding area. By middle Miocene, the rift was formed in some parts with containment basaltic flows. In Pliocene, a huge pyroclastic flow covered the northern part of study area. This characteristic pyroclastic flow deposit is currently observed at the depth of around 2100m in the basin floor by geothermal well, indicates a minimum of 2km of downthrown in the rift basin since its eruption (WoldeGabriel et al. 1990, WoldeGabriel et al, 2000).
In Pleistocene, Wonji Fault Belt (WFB), which is the main spreading axis of MER, is formed at the rift floor, and floor basalt and rhyolite are erupted along WFB. The volcanic activities are characterized by peralkaline fissure basaltic eruptions and rhyolitic eruptions which make volcanoes and calderas. MER was formed as symmetrical depression zone in this period and many lakes appeared and disappeared by obstruction of volcanic deposit and/or climate change.
b. Regional tectonic setting
The initial stage of MER formation is closely related to that of the Red Sea and Aden Sea. In Mesozoic time, north – central MER was bulged. That is deduced by the existence of thick Mesozoic sediments in Kella horst (North of Butajira) and the Blue Nile gorge.
In Oligocene, large and huge volcanic activity created a lava plateau. In early Miocene, three radial rifts might have been formed in the plateau. After that, two rifts spread open and were downthrown to the sea, which became the Red Sea and Aden Sea. The other rift, which was not spread well, became the MER.
Such kind of tectonic activity is considered to have occurred in the initial stage when the continent started splitting, and caused by rising of hot plumes from the mantle (refer to Figure 2.2.1).
Structural and stratigraphic relations of volcanic rocks along both rift escarpments of MER indicate a two-stage rift development. The early phase started during late Oligocene – early Miocene and was characterized by a series of alternating and opposed half grabens. The half-grabens evolved into a symmetrical rift during the late Miocene. The area also was characterized by active rifting during Plio-Pleistocene, around 2000m of subsidence was estimated (WoldeGabriel et al, 1990).
The rift floor is nowadays covered by lakes, lacustrine sediments, basalts from fissure eruptions, and silicic tephra from the nearby Quaternary volcanoes.
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Figure 2.2.1: Schematic Diagram for Development of Red Sea Rift and Aden Sea Rift, and failed African Rift (MER), (Source: http://www3.interscience.wiley.