An integrated assessment of groundwater resources and their sustainable use in the Lake Kyoga basin, Uganda.

Groundwater faces pressures from climate change, population growth and development. Over the Lake Kyoga basin (57,233 km²) in Uganda, threats to groundwater resources are manifested in terms of drying streams and boreholes. The question that remains open is; "what is the sustainability of groundwater use amidst conflicting natural and anthropogenic pressures?". Such a question requires an understanding of the current and future socio-ecological aspects, information that is not readily available. Here, we present preliminary results for a Volkswagen Foundation funded multidisciplinary project that aims to assess the sustainability of groundwater use over the basin, by addressing these objectives; 1) quantify groundwater use under current conditions, 2) characterize the spatial-temporal variability in groundwater storage and recharge that results from groundwater use, 3) assess the perception of groundwater users with respect to threats to sustainable groundwater use, 4) develop suitable indicators and characterize future sustainability of groundwater use considering different scenarios of climate and water use.

Preliminary results (based on the water supply network of Uganda) show that the amount of groundwater withdrawn for domestic use is approximately 7,124 m³/day over the basin, which is similar orders of magnitude with the 5,450 m³/day from the WaterGAP hydrologic model (0.5° x 0.5° resolution). Based on the coarse-scale model simulations, there seems to be a low general impact of human water use on river discharge and changes in basin water storage, indicating that groundwater use is - as simulated by WaterGAP - not a major threat to total water availability. However, uncertainties regarding subsurface characterization, water use estimates and the model resolution of WaterGAP are high, which makes regional modelling approaches and feedback-mechanisms at finer resolutions necessary.

We present the general approach of the project, its recent achievements and the ongoing work that covers set up and evaluation of 1) climate and water use scenario simulations with WaterGAP model and 2) MODFLOW-WEAP simulations at a finer resolution, to evaluate the changes in groundwater storage that result from groundwater use scenarios, in order to provide the basis to answer the research objectives above.