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

Abstract: Wonji Shoa Sugar Estate (WSSE), located in the flood plain of Awash river (Ethiopia), has been 5 under long-term (>60 years) irrigation, industrial activities and agro-chemical usage. In this 6 study, the hydrochemical properties of groundwater bodies available at WSSE have been 7 characterized for quality compositions. Water samples were collected from groundwater 8 monitoring piezometers distributed in the sugarcane plantation and then analysed for physico- 9 chemical quality parameters (pH, EC, major cations and anions) following standard 10 procedures. Other chemical indices (e.g., TDS, TH, MAR, r1, r2) were derived from the 11 measured water quality parameters. The compositional variability and groundwater 12 classification has been presented using the Box and Piper plots. The potential sources of 13 minerals were suggested for each of the considered water sources based on their quality 14 characteristics. Both trilinear Piper plot and meteoric genesis index revealed that groundwater 15 of the area is shallow meteoric water percolation type with a changing of hydrochemical facis 16 and mixing trend. Groundwater of the area, is group 1 (Ca-Mg-HCO3) type, with no dominant 17 cations and HCO3 are the dominant anions. Overall, the study result elucidates that the 18 chemical composition of GW of the area showed spatial variability depending upon the 19 variations in hydrochemical inputs from natural processes and/or anthropogenic activities 20 within the region. The local anthropogenic processes could be discharges from sugar factory, domestic sewage and agricultural activities