SIMULATION OF THE EFFECT OF CLIMATE CHANGE ON THE STREAM-FLOW OF ALA RIVER, AKURE, NIGERIA

Abstract

Climate change is one of the notable changes experienced around the world today and this is as a result of Global warming. The environmental impact of climate change, especially in densely populated developing countries such as Nigeria cannot be overlooked without seeking to provide useful information that will avert the consequences arising from it. Therefore, the aim of this research is to simulate the effect of climate change on the stream-flow of Ala River, Akure, Nigeria. This aim is achieved by projecting climate change, simulating a hydrologic and hydraulic model. Precipitation, one of the changes experienced in the world climate system was considered and projection of precipitation for Ala, Akure was done by statistically downscaling General Circulation Model (GCM) under the Representative Concentration Pathways (RCP 4.5 and RCP 8.0) climate scenario. The projected climate change data alongside other hydrologic parameters were input into Hydrologic Engineering Centre-Hydrologic Modeling System (HEC-HMS) version 4.2 to simulate a hydrologic model to get the peak discharges at different cross-section along the river reach. Finally, the peak discharges were input into Hydrologic Engineering Centre-River Analysis System (HEC-RAS) version 5.0.6 to simulate a hydraulic model to get the water surface and spread distance of the flood. The hydrologic model simulated peak discharges of 275.0 m3/s, 289.1 m3/s, 302.8 m3/s, 329.6 m3/s, 368.9 m3/s, 373.6 m3/s for RCP 4.5 and 298.8 m3/s, 332.3 m3/s, 350.2 m3/s, 374.3 m3/s, 430.7 m3/s, 538.1 m3/s for RCP 8.0 for the year 2020, 2025, 2030, 2045, 2070 and 2100 respectively. The maximum flood inundation of the River Ala catchment which will occur in the year 2100 under the RCP 8.0 climate scenario was simulated to be 2.50 km2. These results suggests that the River Ala catchment is susceptible to high flooding in the future and water resources managers can adopt these results in the implementation of policies and strategies to tackle these projected climate impact on the river stream-flow