Effects of Climate Change and Human Activities on Water Resources in the Comoe River Basin (West Africa)

Abstract

This study was carried out on the Comoe River Basin (78,000 km2) in West Africa where climate change is supposed to affect many sectors like water resources, biodiversity, food, energy, housing, tourism, transportation and health. This study used the GR4J model and three RCM, namely, the COnsortium for SMall scale MOdeling (COSMO) Climate Limited-area Modeling-Community (CCLM4-8-17), the KNMI Regional Atmospheric Climate Model (RACMO) and the Rossby Centre Atmospheric model 4 (RCA4) to assess the robustness of a lumped hydrological model in modelling streamflow and to examine climate change effects on streamflow in the Comoe River Basin using the RCP 4.5 and 8.5 scenarios. Future period’s streamflow were simulated under these scenarios using the GR4J model. The comparison of mean yearly discharge for 2041-2060 and 2081-2100 periods to 1981-2000 periods at M’Basso revealed that flows will decrease respectively for 2041-2060 and 2081-2100 periods about 41% and 45% according to the scenario RCP 4.5 KNMI-RACMO22T model. The decrease of flows following RCP 8.5 for the same periods is about 46% and 44%. High flow and low flow periods are quit the same for the three RCM. The two scenarios and the three RCM reveal an increase of temperature up to 5.6°C for 2041-2060 and 2081-2100 periods at Abidjan, Adiake, Dimbokro, Bondoukou and Bobo Dioulasso stations. Also, temperatures for 2081-2100 period are higher than the ones of 2041-2060 period. The highest values are generally observed in January. Findings from this study revealed an underestimation of mean annual rainfall, 0.4 to 0.6 for RCP4.5 and 0.5 to 0.8 for RCP8.5 for 2041-2060 and 2081-2100 periods. Whereas, SMHI-RCA4 and KNMI-RACMO22T are overestimating mean annual rainfall, 0.2 to 0.3 for RCP4.5 and 0.1 to 0.5 for RCP8.5. Hydrologic and climatic parameters comparison at M’Basso station for 1981-2000, 2041-2060 and 2081-2100 periods revealed an increase of potential evopotranspiration for the two horizons and for the three RCM and a decrease of discharge. The vulnerability of water users to climate change was assessed and communities’ adaptation strategies were defined. Results revealed that 95% of water users are perceiving changes in climate. They have heard of climate change and they attested that there is an increasing occurrence of this phenomenon. Reduced water level in rivers, delay in cropping season, crop failure, new pests and diseases, drop in income and decline in crop yield, food insecurity, changes in economic activity and cropping pattern are different ways that they are experiencing climate change. Findings also revealed that water users use many adaptation strategies like agroforestry, substitution and calendar redefinition, increasing fertilizer application, crops diversification, borrowing from friends and money lenders.