Evaluating the impact of local scale groundwater abstraction on groundwater storage under changing climate in Mpologoma Sub-Catchment, Eastern Uganda

Abstract

Freshwater is an important resource for sustainable socio-economic development around the world. Groundwater that forms 33% of freshwater around the globe is used to support livelihoods and ecosystem services, yet the resource is under pressure from increased water demand, and climate change and climate variability. Limited information on available groundwater resources has led to intensive and unsustainable abstraction of groundwater. In River Mpologoma catchment of the Lake Kyoga basin in Eastern Uganda, over 90% of the catchment population entirely depends on the groundwater. Consequently, since 2000, up to 35% of the constructed groundwater boreholes are non-functional and 5% of them dried up within 5 years of construction. This study therefore aimed at evaluating the likely behavior of groundwater resources in the context of climate change and increased water demand based on projected population growth, socio-economics and urbanization. The Water Evaluation and Planning (WEAP) model was applied to simulate the hydrologic outcomes of increased groundwater demand in three micro catchments of Busia, Malaba, and Namutumba of the River Mpologoma catchment. Estimated potential recharge within the three micro catchments was 175, 135, and 75 MCM/year, respectively. The estimated groundwater abstraction over the period (2003 - 2017) was 2.8, 2.1 and 1.0 MCM in Busia, Malaba and Namutumba micro catchments, respectively; these groundwater abstraction rates in all the micro catchments are still sustainable. The current drying up of boreholes is considered not to be substantially influenced by current groundwater use. Projections for socio economic growth rate of 14% indicated that Namutumba aquifer will take 18 years to deplete under current climate conditions and 17 years under both the RCP 4.5 and RCP 8.5; Malaba aquifer will deplete after 25 years under current climate conditions and 24 years under both the RCP 4.5 and RCP 8.5; Busia aquifer will take 27 years to deplete under current climate conditions and 25 years under both the RCP 4.5 and RCP 8.5. A detailed study to determine actual aquifer architecture, hydraulic parameters and storage is recommended to better understand aquifer response to intensive abstraction over the study area