Abstract

The impact of Climate variability on water resources (surface and ground) was conducted to assess the effect of meteorological forcing on isotopic and recharge characteristics of the granitic and fractured aquifer, located in Pallisa District (Kyoga basin), eastern Uganda. The paper investigated the application of environmental isotopes and using the EARTH Model in determining the groundwater levels response to rainfall of the fractured aquifer. The granitic fractured aquifer is characterized by shallow to deep water table conditions that vary between 5-50 meters below ground level and quick groundwater level response to rainfall events which justified the application of the EARTH model to demonstrate the groundwater level fluctuations of the single monitoring Well-002. Groundwater fluctuations from the observed hydrograph at the monitoring station vary between 8.8 and 13.48 mamsl with an average hydrostatic fluctuation of 11.42 mamsl. Oxygen-18 (δ18O) and deuterium (δ2H) compositions mostly plot below the Local Meteoric Water Line (LMWL) indicating that the surface water and groundwater in the aquifer was exposed to evaporation before or in the recharging process. In the study, groundwater levels response to rainfall events by the EARTH method is the quantitative estimation of groundwater recharge for Pallisa District watershed. Generally, the study findings suggest that applications of precipitation isotopic rainfall data for light and heavy mean monthly rainfall (mean rainfall of 138 mm) and the EARTH model to assess groundwater recharge can improve the understanding of the process under climate variability.

Keywords: Climate variability; Isotopes; Rainfall recharge; Earth model; Groundwater level fluctuation; Fractured aquifer; Pallisa district; Eastern Uganda