ADDIS ABEBA UNIVERSITY SCHOOL OF GRADUATE STUDIES DEPARTMENT OF EARTH SCIENCE GROUNDWATER EVALUATION OF THE WUKRO-GENFEL SUB-BASIN TIGRAY, NORTHERN ETHIOPIA A THESIS SUBMITTED TO THE SCHOOL OF GRADUATE STUDIES OF ADDIS ABABA UNIVERSITY IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTERS IN HYDROGEOLOGY BY DANIEL HAGOS ARAYA July, 2007 Addis Ababa Ethiopia Acknowledgement I would like to express my sincere gratitude to my advisor Dr. Tamiru Alemayehu for his critical comments on the over all thesis work. And also may thanks goes to Dr. Shimeles Fisiha for his humble approach and helping me in interpreting the vertical electrical sounding results. I would also like to thank Relief Society of Tigray (REST) for giving me this marvelous chance to join Addis Ababa University covering all my expenses. All organizations and persons who helped me in providing data and sharing their idea during my work also are thanked. Last but not least , I would like to thank my father ,mother and my wife who stand by me from the beginning to put an end my work and my little sons Elias and Musie who kept waiting during my work time. i Groundwater Evaluation of The Wukro-Genfel Sub-basin Table of contents Acknowledgment ---------------------------------------------------------------------------------i Lists of Contents ---------------------------------------------------------------------------------ii Lists of Figures -----------------------------------------------------------------------------------v Lists of Tables -----------------------------------------------------------------------------------vi Lists of Annexes ---------------------------------------------------------------------------------vi Abstract ------------------------------------------------------------------------------------------vii CHAPTER 1 1 . Introduction........................................................................................1 1.1 LOCATION AND ACCESSIBILITY..............................................................................................2 1.2 CLIMATE..................................................................................................................................3 1.3 GEOMORPHOLOGY AND LAND USE .........................................................................................3 1.4 PREVIOUS WORK.....................................................................................................................6 1.5 OBJECTIVE OF THE STUDY ......................................................................................................6 1.6 METHODOLOGY.......................................................................................................................7 CHAPTER 2 2 Geology .................................................................................................9 2.1 REGIONAL GEOLOGY ..............................................................................................................9 2.1.1 Precambrian Basement complex ...........................................................................9 2.1.1.1 Tsaliet Group........................................................................................................................ 10 2.1.1.2 Tembien Group .................................................................................................................... 11 2.1.1.3 Didikama Formation............................................................................................................ 11 2.1.1.4 Matheos Formation.............................................................................................................. 11 2.1.2 Basement Intrusive...............................................................................................12 2.1.3 Sills, Dykes and Plugs (other intrusion)..............................................................12 2.1.4 Palaeozoic rocks ...................................................................................................12 2.1.4.1 Enticho Sandstone................................................................................................................ 13 2.1.4.2 Edaga Arbi Glacials .............................................................................................................13 2.1.5 Mesozoic Sediments..............................................................................................14 2.1.5.1 Adigrat Sandstone................................................................................................................ 14 2.1.5.2 Antalo Limestone ................................................................................................................. 14 2.1.5.3 Agulae shale.......................................................................................................................... 15 2.1.5.4 Amba Aradom Formation................................................................................................... 15 2.1.6 Tertiary Volcanic..................................................................................................15 2.2 LOCAL GEOLOGY ..................................................................................................................16 2.2.1 Basement ..............................................................................................................17 2.2.1.1 Metavolcanics ....................................................................................................................... 18 2.2.1.2 Metasediment ....................................................................................................................... 19 b) Pebbly Slate........................................................................................................................................... 19 2.2.1.3 Metamorphosed Black Limestone....................................................................................... 20 2.2.1.4 Metamorphosed dolomite dominated Slates. ..................................................................... 20 2.2.2 Palaeozoic Sediments ...........................................................................................21 2.2.2.1 Enticho Sandstone................................................................................................................ 21 2.2.2.2 Edaga Arbi Glacial............................................................................................................... 22 2.2.3 Mesozoic Sediments..............................................................................................23 Daniel Hagos Araya, 2007 ii Groundwater Evaluation of The Wukro-Genfel Sub-basin 2.2.3.1 Adigrat Sandstone................................................................................................................ 24 2.2.3.2 Antalo Limestone ................................................................................................................. 25 2.2.3.3 Agulae Shale ......................................................................................................................... 26 2.2.4 Mekelle Dolerite ...................................................................................................26 2.2.5 Quaternary Alluvial and Colluvial deposits ........................................................26 CHAPTER 3 3 Hydrometeorology .............................................................................29 3.1 PRECIPITATION......................................................................................................................30 3.1.1 Thesien Polygon Method .....................................................................................31 3.1.2 Arithmetic Mean...................................................................................................33 3.1.3 Isohyetal method ..................................................................................................34 3.1.4 Relationships between elevation and depth of precipitation...............................36 3.1.5 Seasonality of Rainfall.........................................................................................37 3.2 TEMPERATURE ......................................................................................................................39 3.3 RELATIVE HUMIDITY ............................................................................................................39 3.4 WIND SPEED ..........................................................................................................................40 3.5 SUNSHINE HOURS ..................................................................................................................41 3.6 EVAPOTRANSPIRATION .........................................................................................................42 3.6.1 Potential Evapotranspiration...............................................................................42 3.6.1.1 Penman combination (Penman –Mentioth) method.......................................................... 42 3.6.1.2 Thornthwaite Equation ....................................................................................................... 48 3.6.1.3 Masmstrom method (1969).................................................................................................. 49 3.6.2 Actual Evapotranspiration...................................................................................49 3.6.2.1 Turc Method (1961) ............................................................................................................. 50 3.6.2.2