Pollution Risk Assessment of Groundwater at Kamkuywa Market Center, Bungoma Using Geospatial Technology

Abstract

Background: Pathogenic contamination of groundwater, due to poor sanitation, has continuously posed a significant health risk to human health. Kamkuywa market center, a peri-urban settlement, relies heavily on shallow wells contamination. This study used GIS-based risk mapping to establish the extent of groundwater pollution by coliforms and determine the relationship between selected risk factors, namely: depth to the water table, distance from a shallow well to the nearest pit latrine, pit latrine depth, soil permeability and ground slope for purposes of establishing the optimal well-pit latrine separation distances under different hydro-geological conditions. Material and Methods: All shallow wells and pit latrines in the study area were mapped and the separation distances compared to the recommended standards. Water samples in 32 shallow wells were collected and analyzed for fecal content. The regression model was used to determine the relationship between coliform concentration and the selected risk factors as well as establish the extent of contamination and optimal distancing. Results: The results indicate that 67.6% of shallow wells did not meet the World Health Organization and the Kenya safe distance criteria. In terms of relationship, pit latrine depth and soil permeability positively correlated with contamination. A negative relationship was established between groundwater contamination and water table depth and no relationship with surface slope. Out of 32 shallow wells sampled for fecal coliform analysis, 31 tested positive for fecal coliforms. Over 75% of the study area was established to be high risk for groundwater contamination. Finally, the predicted optimal distance between wells and pit latrines in the study area ranged between 31m-33m. Conclusion: The study concluded that Kamkuywa Market Center is water scarce as a result of extensive groundwater contamination. Lastly, safe distances can vary from area to area depending on the climatic and hydro-geological conditions of an area.