Hand dug wells, boreholes and springs are developed and used to meet the demands. Especially in the arid and semi-arid parts of the country it remains the sole source of water supply for different uses. Like in many countries, groundwater is the main source of water supply for domestic, irrigation, livestock’s and industrial uses in both urban and rural areas of Ethiopia. According to United Nations Environment Program report (UNEP) approximately one-third of the world’s population depends on groundwater for drinking purpose. Groundwater is the world’s largest accessible freshwater and an important resource for domestic water supply, irrigation, livestock’s, and industrial uses as well as for global food security. Since, this study is based on groundwater from hand dug wells, the conclusions of this study should be further verified using groundwater from deep wells that are drilled in these successions. The intercalated shale beds are the source of sodium and chloride ions. Dissolution of calcite and gypsum, and hydrolysis of feldspars, plagioclase, biotite and pyroxene are the major geochemical processes that control the chemistry of groundwater in the area. Among eight hydrochemical facies identified, Ca-Na-HCO 3 (40%), Ca-HCO 3 (20%), Ca-Mg-Na-HCO 3 (10%) and Ca-Na-HCO 3-SO 4 (10%) types dominate water chemistry. Ca 2+, Na +, HCO - 3 and SO 2- 4 are dominant ions compared to Mg 2+, K +, and Cl - ions which show low to very low concentrations. The results indicate that groundwater is acidic to neutral, fresh, and hard to very hard. The major water bearing formations are gravely sand, weathered shale and weathered and fractured limestone, and intercalated weathered and fractured limestone and mudstone. Twenty groundwater samples were collected from hand dug wells using depth-integrated sampling techniques from both confined and unconfined aquifers. The sub basin is dominated by Paleozoic-Mesozoic sedimentary successions. Groundwater is the main source of water supply in the sub basin extracted using hand dug wells, for domestic, irrigation and livestock uses. This was done by considering a sedimentary aquifer basin, namely the Hantebet sub basin (24.4 km 2), Tekeze basin, northern Ethiopia. The present paper provides evidence of the possible impact of shale-limestone-mudstone successions aquifers on groundwater chemistry by assessing the different hydrogeochemical processes.
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