Evaluation of Groundwater Quality and Potential Pollution Risk Analysis: The Case of Botor Tolay District, Jimma Zone, Oromiya National Regional State, Ethiopia

Abstract

Water quality is determined by physical, chemical and microbiological properties of water. The quality of water degrade through pollution from point and non-point sources. Water quality degradation is one of the major environmental problems of these days. The study was conducted to evaluate the physico-chemical parameters of groundwater quality for drinking and irrigation suitability and to assess the potential pollution risk of groundwater in Botor Tolay district, Jimma Zone, Oromiya National Regional State, Ethiopia. A total of 16 samples were collected from borehole, shallow well, hand dug well and protected springs by representative sampling technique and analyzed for physical and chemical parameters. Electric conductivity, sodium absorption ratio, magnesium hazard, residual sodium carbonate and kelly ratio were evaluated for irrigation suitability assessment. Potential pollution risk of groundwater samples were assessed using D8 flow direction algorithm. The analyzed data was presented by using table, graphs, piper diagram and figures and were compared with WHO guideline value for drinking suitability. The result showed that for all the groundwater samples the concentration of pH, TH, CO3 -2 , Cl- NO3 - and SO4 -2 were below the recommended WHO value which were suitable for drinking in terms of these parameters. For most of the groundwater samples the concentration of EC, TDS, TA, Mg+2 , Na+2, K+2 , Ca+2, F – and Fe+2 were found below the WHO standards thus, suitable for drinking purpose whereas the obtained value of Mn+2 , turbidity and temperature of all the groundwater samples were exceeds the limit of WHO standards which were not suitable for drinking purpose. Interpretation of all physico chemical parameters were carried out using AquaChem software (Version 2014.2), Microsoft excel (Version 2013) and SPSS (Version 20). All groundwater samples were found suitable for irrigation water according to EC and SAR whereas only 50% water sample were suitable based on MH and KR. According to RSC all groundwater samples were suitable for irrigation water except sample S4, S7, S9 and S12. The potential pollution risk assessment of groundwater samples were classified as no, low, medium and high with sample number of 8, 3, 4, and 1, respectively