ASSESSMENT OF GROUNDWATER CONTAMMINATION BY AGRICULTURAL CHEMICALS AND URBAN EFFLUENTS IN ARBAMINCH AREA, SNNPR, ETHIOPIA

Abstract

Groundwater is a major source for all purpose of water requirements and it plays a vital role to human life and economic activities. But unplanned and non-scientific action on groundwater has led to sharp depletion in quantity and degradation in quality of the resource Therefore, the prime focus of this study was to holisticallt understand groundwater contamination by agricultural fertilizers and sewage effluents by evaluating the groundwater contaminant parameters and their spatial distribution using geostatistical methods at Arba Minch University farm. To achieve this objective a total of nine observation wells were established by hand auger manually in study area for sampling of groundwater. These groundwater wells samples were analyzed in the field for physico-chemical parameters (Temperature, pH and EC) and depth to water levels was measured, and in the laboratory for parameters such as BOD, Nitrite, Nitrate and Phosphate. The physico-chemical parameters result were compared to the standard guideline values as recommended by the World Health Organizations (WHO) for drinking and public health in order to have an overview of the present groundwater quality. The results of the Laboratory analysis were examined by the use of the software package ArcGIS and AquaChem. Using GIS interpolation technique with ArcGIS 9.3, spatial distribution maps of BOD, Nitrate, Nitrite and Phosphate have been created. Using AquaChem software package, interpretation and graphical representation methods such as Detection Summary, Map plot and scatter plot of agricultural chemicals and sewage effluents were established. Groundwater level contour map was produced by ArcGIS for the identification of groundwater flow direction to understand pollutant flow direction. According to the overall assessment of the study area, all parameters analyzed for agricultural fertilizers (Nitrate and Phosphate) are below the maximum desirable limits of WHO and from the parameters analyzed for AMU sewage effluents contamination BOD is below the maximum desirable limit of WHO but Nitrite of 66% samples was found to be above the maximum desirable limit of WHO. Groundwater flow direction was identified to be in East-East North direction