Modeling the impact of past and future land cover changes on a reservoir catchment hydrology in Semi-arid, Africa

Abstract

Land-use change influences watershed hydrology and eventually, the sustainability of reservoirs. Understanding how reservoir catchment land use dynamic influences hydrology is imperative to devise effective land management and planning strategies for sustainable management of reservoir storage. This study evaluated the response of hydrological components of the Vea reservoir catchment (a sub-catchment of the White Volta Basin in West Africa) to past, present, and future land-use change scenarios (1985, 1996, 2006, 2020, 2030, 2040) using the Soil Water Assessment Tool (SWAT). The model performed satisfactorily with NSE values of 0.738 and 0.782 for calibration and validation respectively. The land cover change analysis revealed a continuous increase in farmland and built-up areas from 1986 to the projected 2040 resulting in increased Curved Numbers (CN). The model results revealed that an increase in CN from 81.26 to 86.06 between 1986 and projected 2040 resulted in a -7.8% and − 26.2% decrease in ET and base flow respectively, 46.9%, and 5.1% increase in surface runoff, and water yield respectively. Despite the general decline in base flow, the seasonal trend shows that base flow extends to January, indicating that the shallow aquifer store enough water that can be extracted for dry season gardening. While vegetation restoration is critical to reducing eroded sediment yield from the catchment to guarantee reservoir storage, constructing dams and dugouts within the catchment to harness the high surface runoff water for irrigation and livestock watering in the long dry season is also needful.