Assessing the Impact of Climate Change on Hydrological Responses and Sediment Budget in the Ruzizi River Basin

Abstract

Evaluating the effects of climate change on water resources is crucial for their sustainable management, particularly in hydrologically sensitive regions like the Ruzizi River Basin (RRB) in the Great Lakes area of Africa. This research investigates the impact of climate change on hydrological responses and sediment budget within this critical basin, utilizing the Soil and Water Assessment Tool (SWAT) and advanced climate models. The study is grounded in robust methodologies including the use of Coupled Model Intercomparison Project Phase 6 (CMIP6) datasets under Shared Socioeconomic Pathways (SSP) scenarios SSP2-4.5 and SSP5 8.5. These datasets were downscaled and bias-corrected for fourteen stations using the climate model data for hydrologic modeling (CMhyd) tool, employing the distribution mapping method. The methodology involved comprehensive simulations, sensitivity analysis, and rigorous phases of calibration and validation, achieving a Nash-Sutcliffe Efficiency (NSE) of 0.64 and a Coefficient of Determination (R²) of 0.76 during calibration, with validation results showing an NSE of 0.70 and an R² of 0.74. The research meticulously evaluates historical climatic patterns against future projections, analyzing temperature and rainfall trends through Mann-Kendall tests and exploring the spatial distribution of these variables to ascertain changes across different periods. Results indicated a projected decrease in mean annual precipitation by as much as 35% under both SSP2-4.5 and SSP5-8.5 scenarios by mid and end of the century, leading to significant reductions in water yield by nearly 50% and marginal variations in evapotranspiration. These changes suggest profound impacts on water availability and sediment dynamics within the basin. The study underscores the necessity for proactive and adaptive management strategies in water resource planning and agricultural practices, highlighting the critical need for developing responsive policies and infrastructure investments to enhance resilience against the anticipated disruptions of climate change. This approach will ensure the sustainable management of water resources in the Ruzizi River Basin, preparing for an increasingly uncertain future.