ADDIS ABABA UNIVERSITY SCHOOL OF GRADUATE STUDIES GROUNDWATER FLOW SYSTEM AND HYDROCHEMISTRY OF ZIWAY-KOKA CORRIDOR IN THE MAIN ETHIOPIAN RIFT. A THESIS SUBMITTED TO THE SCHOOL OF GRADUTE STUDIES OF ADDIA ABABA UNIVERSITY IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTERS OF SCIENCE IN HYDROGEOLOGY. ABIYU KEBEDE FEBRUARY 2007 ADDIS ABABA GROUNDWATER FLOW SYSTEM AND HYDROCHEMISTRY OF ZIWAY-KOKA CORRIDOR IN THE MAIN ETHIOPIAN RIFT. A THESIS SUBMITTED TO THE SCHOOL OF ADDIS ABABA UNIVERSITY IN PARTIAL FULFILMENT OF THE REQUIRNMENT FOR THE DEGREE OF MASTERS OF SCIENCE IN HYDROGEOLOGY. BY ABIYU KEBEDE FEBRUARY 2007 (1999 E.C) ADDIS ABABA UNIVERSITY SCHOOL OF GRADUATE STUDIES GROUNDWATER FLOW SYSTEM AND HYDROCHEMISTRY OF ZIWAY-KOKA CORRIDOR IN THE MAIN ETHIOPIAN RIFT. BY: ABIYU KEBEDE DEPARTMENT OF EARTH SCIENCE APPROVED BY THE EXAMINING BOARD: DR. BALEMWAL ATNAFU --------------- Chairman, Department Graduate Committee DR. TAMIRU ALEMAYEHU --------------- Advisor ATO ZENAW TESESMA --------------- External Examiner Dr. DAGNACHEW LEGESSES --------------- Internal Examiner ACKNOWLEDGEMENT I wish to express my appreciation for assistance I have received, during the academic year and research of Masters Program. I would like to express my deepest gratitude to my families Getnet A. Birke k. Mulu K. Ashu K. Gizachew K. for their tireless inspiration and encouragement. Special thanks for my sister Mulu Kebede for covering of my personal expenses throughout my stay in the academic years. My special thanks go to my supervisor, Dr. Tamiru Alemayehu for his sound full guidance, constructive criticism, and constant encouragements though out the research and for exposure in Djibouti to present this work at the MAWARI project. I soundly thank CRS, especially Ato Bekele Abaire (Program Manager Watsan), Ato Alemayehu W/M., and Mekides A. for their financial support for the research work and allowance of printing of the thesis report in CRS Office. My sincere thanks to UNICEF/ WASH section for their afford of vehicle and daily allowance during data collection in the field. I am also grateful to Mr. Hans S., Ato Getachew H/ M., Ato Dereje A., W/t Seblewongeil T., and W/t Wossen M. for their cooperative response during stay in the section as an intern. I would like to express my deepest gratitude to Saba Engineering P.L.C. (Ato Negash Awoke), Meki Catholic Church (Eng. Enaugaw), Oromia Water quality controlling Center and Hydro water well drilling and Engineering. Last but not least, I need to thank my friends Shimelis F., Aychiluhim D. and Beza wondwossen for their supportive and encouraging ideas. Groundwater Flow & Hydrochemistry of Ziway-Koka Corridor Abiyu K. Table of Content Content page ACKNOWLDGMENTS…………………………………………………………………………………………………………….i ABSTRACT………………………………………………………………………………………………………………………………Vii 1. INTRODUCTION ............................................................................................................ - 1 - 1.1. GENERAL .................................................................................................................... - 1 - 1.2. PREVIOUS WORK .................................................................................................. - 2 - 1.3. OBJECTIVE OF THE STUDY ....................................................................... - 3 - 2. STUDY SITE DESCRIPTION ..................................................................................... - 5 - 2.1. LOCATION , ACCESSIBILITY AND AERIAL EXTENT ............................ - 5 - 2.2. CLIMATE .................................................................................................................. - 6 - 2.3. TOPOGRAPHY ......................................................................................................... - 7 - 2.4. DRAINAGE ............................................................................................................... - 8 - 2.5. POPULATION .......................................................................................................... - 9 - 2.5.1 Human ......................................................................................................... - 9 - 2.6. GROUND WATER DEVELOPMENT .................................................................. - 10 - 2.6.1. Public Consumption ................................................................................. - 10 - 2.6.2. Irrigation ................................................................................................ - 11 - 3. GEOLOGY ......................................................................................................................... - 12 - 3.1. REGIONAL GEOLOGY ......................................................................................... - 12 - 3.2. GEOLOGY OF THE STUDY AREA ................................................................... - 15 - 3.2.1. MAIN RIFT ............................................................................................ - 15 - 3.2.2. SYN-RIFT .............................................................................................. - 17 - 3.3. GEOLOGICA STRUCTURE ........................................................................... 22 3.3.1. Fault ............................................................................................................. 22 3.3.2. Jointe and Fracture .................................................................................. 22 3.3.3. Caldera ........................................................................................................ 22 3.3.4. Fissure, Cones and Domes ....................................................................... 22 4. SURFACE WATER HYDROLOGY ................................................................................... 25 4.1. SURFACE WATER HYDROLOGY ............................................................................ 25 4.1.1. AWASH RIVER .......................................................................................... 25 4.1.2. MEKI RIVER ............................................................................................... 25 4.1.3. BULBULA RIVER ........................................................................................ 26 ii Groundwater Flow & Hydrochemistry of Ziway-Koka Corridor Abiyu K. 4.1.4. KATAR RIVER ............................................................................................ 26 4.1.5. LAKE ZIWAY ............................................................................................. 26 4.1.6. KOKA DAM ................................................................................................. 28 4.1.7. ELEN LAKE ................................................................................................. 30 5. H Y D R O G E O L O G Y ............................................................................................. 31 5.1. GENERAL ....................................................................................................................... 31 5.2. Hydrogeological units and aquifer systems......................................................... 32 5.2.1. AQUIFER FORMATION ........................................................................... 34 5.2.2. AQUIFER TYPES, DEPTH AND LATERAL EXTENT .......................... 36 5.3 HYDRAULIC CHARACTERISTICS ......................................................................... 37 5.3.1 Pumping test type and duration .............................................................. 37 5.3.2. Hydraulic conductivity .............................................................................. 43 5.3.3. Transmisivity .............................................................................................. 45 5.4. GROUNDWATER SOURCES INVENTORY ......................................................... 45 5.4.1. Hand dug wells ........................................................................................... 45 5.4.2. Boreholes .................................................................................................... 46 6. GROUNDWATER FLOW SYSTEMS .............................................................................. 48 6.1. GENERAL ...................................................................................................................... 48 6.2. GROUND WATER SOURCE, RECHARGE AND DISCHARGE ....................... 49 6.2.1. Ground water Source ................................................................................ 49 6.2.2. Groundwater Recharge ............................................................................. 49 6.2.3. Groundwater Discharge ............................................................................ 51 6.3. GROUNDWATER MOVMENT ................................................................................. 51 6.3.1. Flows in the vicinity of Koka Dam for shallow aquifers ..................... 52 6.3.2. Flows in the vicinity of Lake Ziway from shallow aquifer System .. 53 6.3.3. Flows in the vicinity of Lake Ziway from Deep aquifer System ...... 55 6.3.4. Flows with in the corridor in Shallow aquifer System ....................... 56 6.3.5. Flows with in the corridor in Deep aquifer System ............................ 59 6.3.6. Flows with in the corridor from hand dug Wells near to lakes ....... 63 7. H Y D R O C H E M I S T R Y .................................................................................... 65 7.1. GENERAL ......................................................................................................................