Assessment of Climate and Land Use Change Impacts on the Water Balance Components in the Vea Catchment, West Africa

Abstract

This study assessed the impact of climate and land use/land cover (LULC) change on the water balance components in the Vea catchment, West Africa using the Soil and Water Assessment Tool (SWAT) model. The specific objectives of the study were to, (i) predict the changes in LULC of the Vea catchment based on different LULC change scenarios, (ii) investigate the impact of the Representative Concentration Pathways (RCP4.5) climate change scenario on rainfall, temperature and climate extremes in the future 2020-2049, and (iii) assess the impact of climate and LULC change scenarios on the water balance components. Data used for the study includes, observations (stations and satellite) climate data, Landsat images (1990, 2001, 2011 and 2016) for LULC mapping and prediction, Regional Climate Models (RCMs) and Statistical Downscaling Model- Decision Centric (SDSM-DC) for RCP4.5 scenario for historical and future (2020-2049) period for climate change impact assessment. The study found a decrease in natural vegetation due to cropland expansions over the past years, and a continuous decrease in forest/mixed vegetation and increase in cropland in the future 2025 under business-as-usual (BAU) scenario. The multi-model ensemble mean projected a warmer climate in the future (2020-2049) with a 1.3oC increase in mean annual temperature and a 4.2% increase in mean annual rainfall relative to the baseline (1981-2010) period. Surface runoff was found more sensitive to climate change (-42.7% changes) than land use change under BAU (+18.7 change) and afforestation scenarios (-19.6% change), followed by water yield which under climate change decreased by 43.8% compared to +18.4% and -15.7% changes under BAU and afforestation scenarios of land use change, respectively. The actual evapotranspiration was however found to be less sensitive to land use change (-2.7 and +0.6 % changes) than climate change (+9% changes).