Modelling the impact of land use management on water resources in a tropical inland valley catchment of central Uganda, East Africa

Abstract

A combination of climate change, food demand, population growth, and other driving forces are causing land use and land cover change (LULC) in wetlands of Sub Saharan Africa (SSA). This has a profound effect on water resources, thus it is imperative that such consequences arising from these changes are predicted accurately to support land use management. For that, local scale studies are required to understand the system and to perform scenario analysis. The focus of this study was on small scale inland valleys which are common in SSA. The impact of LULC on the hydrological processes in a tropical inland valley was investigated. A hydrological response unit (HRU)-based (ArcSWAT2012) and a grid-based setup (SWATgrid) of the Soil Water Assessment Tool (SWAT) model are applied. Good model performance was achieved after calibration and validation with daily discharge (R2 and NSE > 0.7 for both model setups). Annual water balance indicates that 849.5 mm representing 65% of precipitation is lost via evapotranspiration. Surface runoff (77.9 mm) and lateral flow (86.5 mm) are the highest contributors to stream flow in the inland valley. Four land use management options are developed in addition to the current land use system, with different water resources conservation levels (Conservation, Slope conservation, Protection of headwater catchment, and Exploitation). There is a strong relationship between the first three management options with decreasing surface runoff, annual discharge and water yield while the fourth option will increase annual discharge and total water yield. This suggests that if poor management and increasing exploitation of the inland valleys persist, the availability of water resources for human consumption and plant growth will decrease. This study contributes to improving the scientific knowledge on the impact of land use change on hydrological processes in the catchment-wetland nexus to support sustainable water resources management.