GROUNDWATER QUALITY ASSESSMENT AND CHARACTERIZATION OF AQUIFERS IN GUDER RIVER WATERSHED, SNNPR, ETHIOPIA

Abstract

Groundwater quality problems and improper management of aquifer either from geogenic or anthropogenic sources has become a thing of health concern and aquifer damage in Guder River Watershed, Southern Ethiopia. This study was conducted to assess groundwater quality and characterize the aquifer. In order to assess the water quality, 30 groundwater samples were gathered and examined for 17 parameters such as pH, temperature, EC, TDS, TH, K+ , Na+ , Ca2+, Mg2+, Fe2+, Cl- , HCO3 - , CO3 2- , SO4 2- , F- , PO4 2- and NO3 - . The research depend on secondary and primary data which was collected from SWWCE, SDCSE, SNNPRWMEB and HZWMED, literature, journals and reports,and field observation on site. The chemical parameters were analyzed and water quality index was determined. To characterize the aquifer of the study area pumping test data, well completion reports, well logs and geology of the area were analyzed. The chemical analysis concentration of the pH, EC, TDS, Na+ , HCO3 - and F shows an increasing trend from the highland water toward the rift floor water along the groundwater flow path. In this regard, water quality indices were considered for drinking and irrigation purposes. Finally, the analytical results were taken to generate the numerical spatial distribution of parameters using geographic information system (GIS) environment. Results of groundwater quality assessment and aquifer characterization show that Ca2+ and HCO3 - are the main cation and anion in the groundwater, respectively. According to the results of the drinking water quality index showed that groundwater sampling were classified 70% as excellent, 27% as good, 3% as poor, and 0% as very poor and unfit for drinking purposes. In addition, Irrigation water quality index illustrated that 100% samplings were placed in the “good” and “ excellent” class. The pumping tests analysis results indicate that the hydraulic conductivity of the study area ranges from 1.26 x 10-5 -4.39 x 100 m/sec and transmissivity were 1.16 x 10-3 -7.71 x 10-2 m 2 /sec this indicates that the productivity of the wells in the watershed ranges from low to high productivity from high land water. In general, the hydraulic conductivity and transmissivity decreases radially from the center of Boyo plain towards the periphery of the area. The findings of this study was not only useful for understanding of groundwater sustainability for different purposes but also useful for supporting water management and protection in the future