DETERMINATION OF THE EXTEND OF GROUNDWATER CONTAMINATION WITHIN THE VICINITY OF KIPKENYO DUMPSITE IN ELDORET MUNICIPALITY, UASIN GISHU COUNTY, KENYA

Abstract

The increasing demand for groundwater as a primary source of water supply has raised concerns about its vulnerability to contamination, particularly in areas surrounding unmanaged dumpsites. Kipkenyo Dumpsite in Eldoret Municipality, Uasin Gishu County, Kenya, presents a potential risk of leachate infiltration into groundwater, threatening water quality and public health. This study aimed to evaluate the impact of leachate contamination in groundwater quality by integrating geoelectrical resistivity surveys and physicochemical analyses. The specific objectives were to determine the physicochemical characteristics of groundwater contamination, map the spatial distribution of leachate contaminant plumes using geoelectrical methods, analyze the vertical and horizontal flow dynamics of leachate, and assess the hydrogeological and environmental factors influencing leachate migration and contaminant transport. This study was anchored in Dacy’s Law developed Darcy's Law in 1856 which is based on experiments that studied the flow of water through sand filters. The study was conducted in the Kipkenyo Dumpsite vicinity, focusing on shallow wells and boreholes used by the local community. A descriptive research design incorporating both geophysical and laboratory analyses was adopted. The sample size comprised groundwater samples were collected from selected wells, with sampling points determined through stratified random and purposive sampling techniques. Physicochemical parameters, including pH, electrical conductivity (EC), total dissolved solids (TDS), nitrates, chlorides, phosphates, sodium and potassium, were analyzed using standard laboratory procedures. The geoelectrical resistivity survey employed two-dimensional (2D) and three-dimensional (3D) resistivity imaging to map subsurface contamination zones. Data analysis involved statistical techniques such as one-way ANOVA to assess spatial variations in water quality parameters, and geophysical inversion modeling to interpret resistivity variations indicative of leachate infiltration pathways. Results indicated that groundwater quality parameters varied across different wells, with pH levels ranging from 5.94 to 11.70, electrical conductivity from 42 to 113 μS/cm, total dissolved solids from 21 to 57 ppm, nitrate from 0.01 to 0.67 mg/L, chloride from 1.90 to 4.40 mg/L, phosphate from 0.26 to 1.04 mg/L, sodium from 5 to 10 mg/L, and potassium from 6 to 58 mg/L, suggesting potential leachate contamination. Further, the findings revealed significant variations (p<0.05) in physicochemical parameters across different wells, with some locations exhibiting elevated ion concentrations linked to leachate percolation. While most parameters remained within World Health Organization (WHO) and National Environment Management Authority (NEMA) limits, localized areas displayed elevated levels of pH and ion concentrations, indicating contamination hotspots. Geoelectrical resistivity imaging identified subsurface zones with low resistivity values, suggesting potential leachate infiltration pathways and groundwater contamination zones. The findings further indicated that groundwater contamination was not uniform across the study area, with hydro geological conditions influencing contaminant transport and distribution. The study concluded that leachate infiltration from Kipkenyo Dumpsite may pose a potential risk to groundwater quality, with localized contamination requiring continuous monitoring. The study recommended the implementation of proper waste management strategies, regular groundwater quality assessments and the establishment of protective buffer zones to mitigate contamination risks. Additionally, future research should incorporate seasonal variations to better understand leachate dynamics under different climatic conditions