Author(s): Grmay Kassa
This paper assesses the groundwater quality and evaluates its quality for drinking purpose using GIS technology and Water Quality Index (WQI) approach and compare with WHO and Ethiopia water quality standards in Adigrat area (38.94 km2) in Tigray, northern Ethiopia. Chemical composition of the groundwater in the area varies widely depending up on the human activities. A total of 22 (13, 4, 4 and 1 from Bore hole, shallow wells, 4 handug well and reservoirs respectively), Depth integrated groundwater samples were collected by purpose sampling technique. These samples were analyzed for their Physico- chemical components. 26 physical and chemical parameters were assessed to evaluate the groundwater quality for drinking use and the Na+, Ca+2 and Mg+2 from cation and Cl-, HCO3-and SO4-2 from anions are the major ions. The groundwater is suitable for drinking purpose with respect to pH, EC, TDS and hardness as CaCO3 as well as physical parameters but, with parameters of Alkalinity and total hardness, iron, calcium, magnesium and chromium concentration, the groundwater needs some water treatment for quality adjustment. It is also suitable for drinking purpose taking in to account all anionic concentrations (SO4-2, PO4-2, NO3-2, NO2-, Cl- , F- and HCO3-). The ionic concentration and the chemical parameters, generally is high around the town and the old waste disposal sites and in the highly cultivated agricultural fields where point and non sources of domestic, factories as well as feltrizer beside the nature sources. 95.45% of the water quality index is classified under excellent but, 4.55% indicated the water quality index poor and unsuitable class and the groundwater is suitable generally with some restrictions. The objectionable groundwater is restricted around the town with main of contaminants domestic and factories wastes. The hydro chemical data reveal that the groundwater of the study region consists of six hydro chemical facies, Including Ca-Mg-HCO3-SO4, Ca-SO4-HCO3, Mg-Ca-SO4-HCo3, Ca-Mg-SO4-HCO3, Mg- Ca -HCO3-SO4and Ca-HCO3-SO4.