Seasonal Variability of Groundwater Levels, Horton Infiltration Constant and Soil Moisture Content in Coastal Aquifers Case Study-Kilifi, Kenya

Abstract

Infiltration is important in determining the surface runoff, groundwater recharge, evapotranspiration, soil erosion, and transport of chemicals on surface and in subsurface waters. Kilifi County heavily depends on groundwater exploitation resulting to poor well drilling, overexploitation and salt water intrusion problems ; there is no monitoring data in place. This research employs the Horton infiltration model to determine infiltration parameters, the soil moisture probe to determine the soil moisture content and the dipper to measure the groundwater levels. Results reveal that; 56% of the boreholes had either; broken hand pumps, malfunctioning generators, had caved in, or had been abandoned. 172 boreholes and shallow wells identified, were predominantly in urban centres, 90% did not adhere to the environmental, safety and construction standards. Rainfall variability had little impact on the deep wells but groundwater levels in shallow wells increased in the wet season. Soil moisture content in Kilifi South was high pointing to the prevalent swampy clay soil. Results from double ring infiltrometer indicate that initial soil moisture content is critical in determining the rate of infiltration. The infiltration rate was lower in the wet season and high in dry season. The Horton decay constant (k) was equally higher during the dry season