Hydrogeological characterization of the groundwater resources in Lwengo District, Central Uganda.

Abstract

This study presents a hydrogeological characterization of groundwater resources in Lwengo District, Central Uganda, focusing on aquifer properties, groundwater flow dynamics, hydrochemical composition and the factors influencing groundwater recharge using secondary datasets from the Directorate of Water Resources Management (DWRM/MWE), including borehole logs, aquifer test reports, topographical information and hydrochemical datasets. Aquifer parameters were estimated from four long-duration pumping tests using the Theis (1935) and Cooper-Jacob (1946) methods, while hydrochemical analyses were used to classify groundwater types and identify controlling geochemical processes. Results indicate that groundwater occurs mainly within weathered and fractured crystalline basement rocks under confined to semi-confined conditions. Water bearing zones occur at depths of 22–50 m below ground level, with static water levels ranging from 8–20 m. Aquifer parameters indicate low to moderate productivity, with transmissivity values of 0.3–5.5 m²/day, hydraulic conductivity of 0.02–0.2 m/day and storativity ranging from 2 × 10⁻⁵ to 1 × 10⁻⁴. Groundwater recharge is influenced by rainfall, topography, land use and the weathered and fractured basement geology, resulting in spatial variability across the district. Groundwater is predominantly characterized by Ca-Mg-HCO₃ and Ca-Mg-SO₄-Cl facies, controlled mainly by rock–water interaction and silicate weathering. Moderate mineralization was observed, while elevated nitrate and phosphate concentrations in some boreholes suggest localized agricultural and sanitation impacts. The findings demonstrate that groundwater occurrence in Lwengo District is structurally controlled and spatially heterogeneous, highlighting the importance of integrating geological, structural, geophysical, recharge and water quality assessments for sustainable groundwater resource development and management.