Future Impact of Climate and Land Use Change on Streamflow in the Rokel-Seli River Basin, Sierra Leone

Abstract

Water availability in river basins is a global concern due to its increasing demand, thus making it essential for a nation's development. Understanding the future effect of climate and land use land cover (LULC) changes on the water cycle is fundamental for consistent access to water resources. This study's objective is to use a physically based semi-distributed model to explore streamflow seasonal projection of the Rokel-Seli River basin (RSRB) using separate and combined impacts of climate and LULC changes from 2021 to 2060, under projected scenarios (RCP2.6 and RCP8.5). The LULC results showed agricultural, urban, and bare land expansion at the expense of forest land historically, with a projected increase in bare and urban land. The hydrological model calibration and validation of statistical indicators for R and P factors, NSE, R², and KGE performed very well, despite limited data, in replicating the flows. The mean seasonal streamflow is projected to decrease due to different LULC changes, with urban and bare land expansion. The projected streamflow decrease is noticeable under climate change compared with LULC change. As various aspects are responsible for both changes (farming, deforestation, infrastructural development, mining and hydropower supply), this study will enable land and water management authorities to develop suitable strategies to enhance streamflow sustainability in a changing environment.