Abstract
The impact of climate and land use/land cover (LULC) change continues to threaten water resources availability for the agriculturally used inland valley wetlands and their catchments in East Africa. This study assessed climate and LULC change impacts on the hydrological processes of a tropical headwater inland valley catchment in Uganda. The hydrological model Soil and Water Assessment Tool (SWAT) was applied to analyze climate and LULC change impacts on the hydrological processes. An ensemble of six regional climate models (RCMs) from the Coordinated Regional Downscaling Experiment for two Representative Concentration Pathways (RCPs), RCP4.5 and RCP8.5, were used for climate change assessment for historical (1976–2005) and future climate (2021–2050). Four LULC scenarios defined as exploitation, total conservation, slope conservation, and protection of headwater catchment were considered. The results indicate an increase in precipitation by 7.4% and 21.8% of the annual averages in the future under RCP4.5 and RCP8.5, respectively. Future wet conditions are more pronounced in the short rainy season than in the long rainy season. Flooding intensity is likely to increase during the rainy season with low flows more pronounced in the dry season. Increases in future annual averages of water yield (29.0% and 42.7% under RCP4.5 and RCP8.5, respectively) and surface runoff (37.6% and 51.8% under RCP4.5 and RCP8.5, respectively) relative to the historical simulations are projected. LULC and climate change individually will cause changes in the inland valley hydrological processes, but more pronounced changes are expected if the drivers are combined, although LULC changes will have a dominant influence. Adoption of total conservation, slope conservation and protection of headwater catchment LULC scenarios will significantly reduce climate change impacts on water resources in the inland valley. Thus, if sustainable climate-smart management practices are adopted, the availability of water resources for human consumption and agricultural production will increase.
Highlights
The impacts of climate change such as rising temperatures and unpredictable precipitation intensity and patterns have become undeniably unequivocal in East Africa [1,2,3], impacting the fragile ecosystems such as wetlands in the region
The comparison between daily observed and simulated discharge for the calibration and validation periods indicated the ability of the Soil and Water Assessment Tool (SWAT) model to capture the flows in the inland valley, as evidenced by the model performance statistical measures (R2, NSE and KGE) (Figure 3)
An ensemble of six bias-corrected regional climate models (RCMs) from the CORDEX-Africa project were utilized in the SWAT model as input to simulate the hydrological response to climate change by the mid-21st century
Summary
The impacts of climate change such as rising temperatures and unpredictable precipitation intensity and patterns have become undeniably unequivocal in East Africa [1,2,3], impacting the fragile ecosystems such as wetlands in the region. Human and environmental stressors such as land use changes associated with rapid urbanization and uncoordinated expansion of intensive agricultural production in these wetlands negatively impair their water availability, quality and other ecosystem services and functioning [2,4,5]. Wetlands offer numerous ecosystem services and functions ranging from provisioning to regulation and cultural services [9,10,11,12]. Their integrity in offering ecosystem services and functions are being jeopardized due to factors such as anthropogenic activities, including population growth, degradation of arable upland soils, and increasing unpredictability of precipitation [13,14]. Inland valleys are the most affected wetland types and are seen to possess a huge potential for agricultural production due to their soil water availability throughout the year and the inherent soil fertility [15,16,17,18], which encourage continuous agricultural production
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