ASSESSMENT OF CURRENT AND FUTURE CLIMATE CHANGE IMPACT ON SMALL DAMS’ SEDIMENTATION IN THE BENINESE SECTION OF THE NIGER RIVER BASIN

Abstract

The evaluation of the relationship between climate changes and sedimentation in dams constitutes a pivotal aspect of environmental research. This study focused on the Beninese Section of the Niger River Basin and assessed the intricate interplay between climate change and sedimentation of small dams in the area. Current heavy rainfall trends were determined for 15 rain gauges by non-parametric trend detection methods followed by the projection of future heavy rainfall patterns using the WRF-Had GEM2 and WRF-GFDL models. Soil and Water Assessment Tool (SWAT) was also configured, calibrated, and validated for the Sota catchment. The results revealed that for the period 1980 - 2022, no spatial pattern emerged in heavy rainfall, with both positive and negative trends recorded. Noteworthy break years in 2006 impacted Natitingou and Djougou stations distinctly. Also, the WRF-GFDL model simulated well the rainfall event in the northern Benin. However, the HadGEM2 model projected predominantly positive heavy rainfall trends, indicating potential increased intensity under RCP 4.5 scenario in the Beninese Section of the Niger River Basin for the period 2020-2049. Sediment yield using the SWAT model indicated an average of 18.6 ton/ha/year across the Sota basin located in the Niger River Basin, posing challenges in southeast regions. The model predicted a decrease of the sediment load to 12.8 ton/ha/year at the horizon 2049 despite the simulated increase of discharge in the area. This study offers insights into the dynamic relationship between climate-induced changes in heavy rainfall and the consequential sedimentation of small dams, contributing to the understanding of sedimentation processes in northern Benin.