Groundwater Potential of Upper Tumet Catchment
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Groundwater potential of 34°30'0"E 34°40'0"E 34°50'0"E Upper Tumet catchment: To Gizen 10°30'0"N BEBE BEBE 10°30'0"N SAEDA A Guide for Groundwater BEBE TOBE Road SHOGEL Specialists Towns BEBE Kebele boundary MALLO This is one of three fliers produced to illustrate how, TUMET MEKUWAR Menge woreda BENE based on the same information, different types of maps EWADANE can target different types of users. We have three komesha woreda BALGAL TUMET MENDERA different users in mind: map developers such as GIS MANAJA ALFASHER GUAGUYO BERBER specialists, deep users (this present map), such as JEMEA HALFA hydro-geologists who have a good technical understanding KUDIYU 02 BELL FERFER KUDIYU 01 Menge BALA FAYA of the input data and shallow users such as planners who ABORA KESHEFA DIGNIDO BELDIWESA ABUNDUDU 10°20'0"N do not necessarily understand input data but need to use 10°20'0"N ASHURA METEMA TSLENGER groundwater information for planning purposes. AUSHMEN TUMET ALGELA KARTUM AZIZ TUMET JEDEDA This map shows the groundwater potential of Upper OBE TUMET MENGDEL ABJINDO Tumet catchment. The map can help the planning and TUMET BARIA AFIGALA TUMET ADMUGU GOSHO implementation of new water supplies, by indicating HOLO ABAGUSHA where groundwater resources are likely to be more SHAGA KELSHE YEJIE MEGELE KETEMA plentiful, easier to develop, and sustainable throughout FATSKO SHEKETO 036Kilometers TSRA ALMETEMA ® the year; The map also shows the kebele and woreda o Asosa boundaries, the towns, and all-weather roads, so that T 34°30'0"E 34°40'0"E 34°50'0"E information on population and water demand, and village access, can be combined with groundwater availability. Groundwater Potential Groundwater Excellent groundwatwer potential potential Explanation Good groundwater potential Moderate to high groundwater storage; groundwater easily found and can be successfully exploited for village supplies using hand-dug Excellent wells. Larger supplies likely to be possible from machine drilled or deep wells. Moderate groundwater potential Moderate groundwater storage; groundwater found relatively easily and in most cases can be successfully exploited for village supplies Poor groundwater potential Good through hand-dug wells. Sometimes, machine-drilled shallow wells may be needed even for village supplies. Very poor groundwater potential Groundwater occurs only in certain areas, such as where weathering is particularly deep or where the rock is particularly fractured near Moderate a fault. Low to moderate groundwater storage; hand dug wells likely to dry up in longer drought periods and sometimes even in normal This flier was produced by dry seasons, but machine-drilled wells can usually provide sustainable village supplies if carefully sited, e.g. using geophysical surveying. Gezahegn Lemacha based on Groundwater difficult to find; low and seasonal groundwater storage; careful siting needed to develop even hand-dug wells, and his MSc work in Upper Tumet Poor machine-drilled wells are unlikely to more successful. Wells typically dry up shortly after the rainy season ends. catchment, Menge and Komosha woredas, Benishangul-Gumuz Groundwater difficult to find; very low and seasonal groundwater storage; even carefully sited hand-dug wells only provide small Very poor amounts of water during the rainy season, and dry up at the end of the rains. Machine-drilled wells are unlikely to be more successful. region, Ethiopia for WaterAid Ethiopia and RIPPLE. Main controls on groundwater potential The groundwater potential map is based on a combination of eight different hydro-geological factors, but three of these factors are the most important at controlling groundwater potential: lithology, structural lineaments and the depth of weathering. These three input layers are shown and explained below. Lineament Map Lithologic Map Depth of Weathering Map 672000 681000 690000 699000 708000 672000 681000 690000 699000 708000 672000 681000 690000 699000 708000 Rock Type Aquiclude 1162000 1162000 1162000 1162000 1162000 Low Productive 1162000 Very Deep (>18m) Moderately productive Deep (11-18m) Moderately Deep (9-11m) Shallow (6-9m) 1153000 1153000 1153000 1153000 1153000 1153000 Study_Area Very Shallow (<6m) Lineament 1144000 1144000 1144000 1144000 1144000 1144000 1135000 1135000 1135000 1135000 1135000 4 1135000 4 Kilometers Kilometers 4 Meters 010205 010205 06,250 12,500 25,000 1126000 1126000 1126000 1126000 1126000 672000 681000 690000 699000 708000 1126000 672000 681000 690000 699000 708000 672000 681000 690000 699000 708000 Lineaments are structural lines such as faults, Groundwater is found in rock pores and/or In hard rocks with little primary porosity and which in many circumstances have created or fractures. The rock lithology (type of rock) is permeability, groundwater can be found in increased secondary porosity and permeability the main control on the primary porosity and weathered zoones which form in the uppermost by fracturing the rocks. Lineaments can permeability. Higher porosity contributes to parts of the rock, near the ground surface. The therefore contain groundwater, even in rocks higher groundwater storage, and higher thicker the weathered zone is, the more with low porosity and permeability. permeability contributes to higher groundwater can be stored and the better potential groundwater yields. In this catchment there is for larger and year-round sustainable yields. are two main lithology types – crystalline. RiPPLE is a DFID-funded Research Precambrian basement rocks (mainly schists Programme Consortium. You can find and metagranitic rocks), which have secondary out more about RiPPLE’s work at: fracture permeability, form low productivity aquifers aor occasionally aquicludes (contains www.rippleethiopia.org essentially no groundwater); and tertiary volcanics, which have primary permeability or by emailing: from vertical cooling joints, and which form [email protected] moderately productive aquifers..