An Assessment of Climate Change Impact on Water Related Ecosystem Services (WRES) including Hydropower Potential in the Kandadji Catchment in West Africa

Abstract

This study assesses the impacts of climate change on water related ecosystem services (WRES) including hydropower potential in the Kandadji catchment in West Africa using the conceptual rainfall-runoff modeling HBV-Light and two regional climate simulation datasets. Daily observations of streamflow, rainfall, and potential evapotranspiration (derived from temperature, wind speed, air humidity and solar radiation) from meteorological and hydrological stations within the catchment for the period of 1980 to 2011 were used to calibrate, and validate the HBV model prior to the streamflow prediction. The Coefficient of determination, Model efficiency (NSE), and Kling-Gupta efficiency (KGE) achieved during the calibration and validation ranged between 0.69 and 0.84. Future climate signals of rainfall and temperature,wind speed and relative humidity were analysed using two regional climate model datasets (GCM-RCMs) retrieved from WASCAL high resolution regional climate simulation under RCP 4.5.The evaluation of historical simulated climate datasets showed diversions from the observations, therefore simulated climate data were corrected using the quantile mapping bias correction method. The calibrated HBV model was then forced with the spatial average of the RCM-based hydro-climate variables to simulate future daily runoff at the catchment outlet for the historical (1980-2005), the near future (2020-2049) and future (2070-2099). Compared to the reference period, projections in the catchment showed (i) a mixed trend for precipitation (+310 to -102 mm/year), (ii) increase of temperature (up to 330C), and (iii) both increase and decrease trends for discharge (+185 to – 68 mm/year) with both bias corrected and non bias corrceted climate data. Tis mixed trend for projected discharge suggests that both discharge increase and decrease should be considered in climate adaptation strategies in the region. The study further suggests investigations to be extended on arrigated agriculture development as well as hydropower production considering the estimated high potentiels for these water related ecosystem services in the catchment. However, projections indicated that the additional domestic water demand created by the population growth will not be fulfilled by surface water in the future under RCP4.5.The overall findings of the study can assist the water managers and the community of the Kandadji catchment in managing the usage of future water resources in a more sustainable way.