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Groundwater property and composition variability under long-term irrigated area of Wonji Plain, Ethiopia

Dinka, Megersa Olumana
Journal of water and land development 2019 v.41 no.1 pp. 37-46
absorption, anions, anthropogenic activities, bicarbonates, cations, electrical conductivity, floodplains, groundwater, hydrochemistry, irrigated farming, irrigation, magnesium, minerals, mixing, monitoring, pH, piezometers, rivers, sewage, sugar industry, sugarcane, sugars, total dissolved solids, water hardness, Ethiopia
Wonji Shoa Sugar Estate (WSSE), located in the flood plain of the Awash River (Ethiopia), has been under long-term (>60 years) irrigation, industrial activities and agro-chemical usage. In this study, the hydrochemical properties of groundwater bodies available at WSSE have been characterized for quality compositions. Water samples were collected from groundwater monitoring piezometers distributed in the sugarcane plantation and then analysed for physico-chemical quality parameters (pH, EC, major cations and anions) following standard procedures. Other chemical indices (e.g., total dissolved solids (TDS), total hardness (TH), magnesium absorption ratio (MAR), base exchange (r₁), meteoric genesis (r₂)) were derived from the measured water quality parameters. The compositional variability and groundwater classification has been presented using the Box and Piper plots. The potential sources of minerals were suggested for each of the considered water sources based on their quality characteristics. Both trilinear Piper plot and meteoric genesis index revealed that groundwater of the area is shallow meteoric water percolation type with a changing of hydrochemical facies and mixing trend. Groundwater of the area, is group 1 (Ca-Mg-HCO₃) type, with no dominant cations and HCO₃ are the dominant anions. Overall, the study result elucidates that the chemical composition of GW of the area showed spatial variability depending upon the variations in hydrochemical inputs from natural processes and/or anthropogenic activities within the region. The local anthropogenic processes could be discharges from sugar factory, domestic sewage and agricultural activities.