Evaluation of the Potential of Kericho Aquifer as a Source of Groundwater

Abstract

Groundwater is a major source of water supply in Kericho County, Kenya. However, this water source is threatened by the rise in the human population and climate change. Under these conditions, it is crucial to assess the sustainability of the groundwater resource in Kericho County. Thus, this study aimed to characterize hydraulic and hydrogeological parameters controlling groundwater occurrence and also to investigate the potential of groundwater in Kericho County, Kenya. To achieve this objective, the study utilized a combination of geophysical and pumping test data. Consequently, fifty Vertical Electric Soundings (VES) were carried out to determine the aquifer properties of the study area. Further, seven out of fifty surveyed sites were drilled to depths ranging between 30m and 230m, and test pumping was done for 24 hours. The GIS-based conceptual groundwater model was developed using Groundwater Modelling System (GMS) software. The model was calibrated in a steady state. Geophysical results show that the average hydraulic conductivity in the study area varies from 1.96 m/day to 6.2 m/day. The transmissivity ranged from 35.83 m2/day to 5166.4 m2 /day, while the yield ranged between 0.7 and 9.7 m3/hr. The aquifer hydraulic parameters determined from geophysical and pumping test data were analysed using one-way analysis of variance (ANOVA). The results show no significant difference (p = 0.95> 0.05) on hydraulic conductivity between geophysical and pumping test methods. Results from calibration showed hydraulic conductivity values varying from 0.28 to 1.12 m/d, while the recharge rates ranged from 0.5 to 2.2 x 10-4 m/d. A predictive run was done in the calibrated model to examine the aquifer's response to abstractions under three different scenarios of increasing water demand due to population growth; the effects of climate change and a combination of both increasing water demand and climate change. The results showed that excessive pumping rates interfere with the surface water and groundwater interactions. Also, locations near the river recorded a slight decline in the constant head. However, the recharge rate was higher than the abstraction, indicating that groundwater will remain sustainable as the primary source of water supply for the residents. Moreover, the volumetric budget for the three scenarios shows that the aquifer has sufficient water supply to be used by the population despite the effects of climate change and population growth. These findings provide vital information for the sustainable and effective planning and management of groundwater resources for the Kericho Aquifer