Assessment of Climate Change Impact on Water Resources in the Senegal River Basin at Bakel

Abstract

In this study we assess the impact of climate change on water resources by using uncorrected and bias corrected data from the regional climate model REMO simulations over the Senegal River Basin (SRB). Both simulations were used as input of the Max Planck Institute for Meteorology – Hydrological Model (MPI-HM) over the Upper Senegal Basin (USB). Applying the bias correction simulations of present day climate (1971-2000) substantially improved for both temporal and spatial variations of the analyzed climate parameters (precipitation, temperature) when compared to interpolated gridded observations and station data. Additionally, the bias corrected input give better representation of the mean river flow, the low flows (10th percentile) and the high flows (90th percentile) at the outlet of the USB. For the future, the regional climate model projections for precipitation show a general decrease by the end of 21st century (2071-2100) for both scenarios (Representative Concentration Pathways RCP4.5 and RCP8.5) and datasets in the majority of the basin, except the Guinean highlands where a slight increase is found. In case of the potential changes of the maximum consecutive number of dry days and wet days, the northern basin is likely to face the most pronounced increase of dry days and decrease of wet days, although a slight increase of heavy rainfall is found with similar spatial patterns in both data. Higher decadal variability of the maximum 5-day precipitation with the uncorrected data in RCP8.5 is projected, while uncorrected and bias corrected data depict similar temporal variability for extremely wet days. Furthermore, a general temperature increase is projected over the entire basin for both scenarios, but more pronounced under the RCP8.5 scenario. Warm night’s percent is found to be higher than warm day’s percent. As for the potential changes of the basin’s hydrology, a general decrease of river discharge, runoff, actual evapotranspiration, soil moisture is found under RCP4.5 and RCP8.5 in all simulations. The decrease is higher under RCP8.5 with uncorrected data in the northern basin. However, there are some localized increases of runoff in some parts of the basin (e.g. Guinean Highlands). Furthermore, the available water resources are projected to substantially decrease by more than -50% in the majority of the basin for all data, except the southern basin in Guinea where no change is projected. The impact of the bias correction on the projected climate change signal, affects mainly the magnitude of the signal rather than its direction of change although some modifications may occur in particular months and localities.