Prepared in cooperation with the United States Geological Survey Groundwater Exploration and Assessment in the Eastern Lowlands and Associated Highlands of the Ogaden Basin Area, Eastern Ethiopia: Phase 1 Final Technical Report By Saud Amer, Alain Gachet, Wayne R. Belcher, James R. Bartolino, and Candice B. Hopkins Contents EXECUTIVE SUMMARY ............................................................................................................................................... 1 1. Introduction ................................................................................................................................................................ 4 1.1. Background ......................................................................................................................................................... 4 1.2. Purpose and scope ............................................................................................................................................. 5 2. Study Area ................................................................................................................................................................. 6 2.1. Geographic location ............................................................................................................................................ 6 2.2. Climate ................................................................................................................................................................ 7 3. Geology ..................................................................................................................................................................... 7 3.1. General geologic setting .................................................................................................................................... 7 3.2. Stratigraphy ......................................................................................................................................................... 8 3.3. Derived geologic map ........................................................................................................................................11 3.4. Geologic structure ..............................................................................................................................................14 3.4.1. General setting ............................................................................................................................................14 3.4.2. Lineament (fracture) Analysis ......................................................................................................................15 4. WATEX© (WATerEXploration) Process ...................................................................................................................16 4.1. WATEX© methodology ......................................................................................................................................17 4.1.1. Size and shape of the WATEX© bright anomaly .........................................................................................17 4.1.2 Amount of upstream watershed drainage .....................................................................................................17 4.1.3. Hydrogeologic Considerations .....................................................................................................................18 4.1.4. Major fault structures ...................................................................................................................................18 4.1.5. Riverbed slope and structural dip ................................................................................................................18 4.2. Summary of WATEX© results ............................................................................................................................18 4.2.1. East Karamara aquifer structure ..................................................................................................................19 4.2.2. Other features .............................................................................................................................................21 5. GEOCHEMISTRY .....................................................................................................................................................21 5.1. Available Information from Reports and UNESCO Database.............................................................................21 5.2. Findings from Previous Reports .........................................................................................................................22 5.3. Findings from country-wide database ................................................................................................................23 5.4. Analytical results from USAID wells drilled by IRC .............................................................................................23 6. HYDROGEOLOGIC FRAMEWORK .........................................................................................................................24 6.1. Water-level information ......................................................................................................................................25 6.2. Hydrogeologic units............................................................................................................................................29 6.3. Hydraulic properties of primary aquifers .............................................................................................................31 6.4. Water budget for the Groundwater System ........................................................................................................32 6.4.1. Recharge estimates.....................................................................................................................................34 6.4.2. Volume of potentially recoverable groundwater ...........................................................................................35 6.5. Perennial yield ...................................................................................................................................................35 6.6. Summary description of the hydrogeologic framework .......................................................................................36 7. Analysis of drilling success for USAID wells .............................................................................................................37 7.1. Economic analysis of well success rates ...........................................................................................................38 7.3 Cost/benefit analysis for the WATEX© Process ..................................................................................................39 8. Summary and suggestions for future work ...............................................................................................................42 8.1. Summary of results ............................................................................................................................................42 8.2. Applications implementation ..............................................................................................................................42 8.3. Recommendations for future work .....................................................................................................................43 8.3.1. Recharge estimates.....................................................................................................................................43 8.3.2. Volumetric analysis and visualization of the hydrogeologic framework .......................................................44 ii 8.3.3. Hydraulic properties.....................................................................................................................................44 9. References ...............................................................................................................................................................45 Appendices ...................................................................................................................................................................47 Appendix 1: List of products delivered ......................................................................................................................47 Appendix 2: Capacity building ...................................................................................................................................48 Figures Figure 1. The Eastern lowlands and associated highlands of the Ogaden Basin area, eastern Ethiopia. ..................... 6 Figure 2. Lithostratigraphy and lithology between Mandera Ogaden in Ethiopia , South-West of the survey area, and Mudugh Basins in Somalia, South-East of the survey area (From Fugro Robertson Limited, 2007) ............. 9 Figure 3. Comparison of published geologic map (left) with Landsat Sultan-processed image (right) ........................ 11 Figure 4. Revised geologic and structural map of the Ogaden Basin Area, Eastern Ethiopia based on processed Landsat 7 images (Sultan Processed), radar, SRTM and WATEX Processed image. .............................. 13 Figure 5. Cross section illustrating the southern part of the Marda Fault System between the oil wells of Calub-1, XEF-2, and Las Anod, outside of the current study area (Author Sestini 1993 from