Abstract

Global climate change (cc) might have severe impacts on every economy, and water resource is not an exception. The rainwater harvest (RWH) is considered a substitute water source, mostly in developing nations. The study presents the climate change (cc) impact on Edo State, Nigeria's rainwater harvesting system. Future daily precipitation was statistically-downscaled from an ensemble of three (3) general circulation models (GCMs) derived with climate change scenario (RCP 4.5) for the 2040s (2030-2060) and 2080 (2070-2100). Historical precipitation data from 1980- 2010 were extracted from CRU 2.1 from eighteen (18) meteorological stations over the study region. Comparing the baseline and projected precipitation from all the GCMs simulation run showed that rainfall events decreased for the periods the 2040s and 2080s. The Centre for Canadian Climate Modeling & Analysis (CCCMA) model predicted the highest precipitation reductions of 15.4% and 24.4% for 2030-2060 and 2070-2100. In contrast, MPI projected 8.4% and 12.4% for the two future time slots. The changes in precipitation datasets were used to estimate future harvestable rainwater. Conversely, the selected GCMs predicted decreases in RWH for 2030-2060 and 2070-2100 in response to the historical period (1980-2010). Predicted changes in rainfall events affect the RWH system's performance, and thus, in turn, could force 2.1 million and 2.7 million people out of water security in the near and long term.