Estimating the effect of climate change on water resources: Integrated use of climate and hydrological models in the Werii watershed of the Tekeze river basin, Northern Ethiopia

This paper presents the effect of climate change on water resources in the Werii watershed (1797 km2) using climate (SDSM) and hydrological (WetSpa) models. A fully distributed model (WetSpa) was used to simulate the water resources of the base (2004-2010) and future (2015-2050) periods. The digital elevation model (DEM), land-use, soil and hydro-meteorological features of the Werii watershed were used as inputs to the WetSpa model. Likewise, the statistical downscaling model (SDSM) was used to downscale climate projections from the regional climate model (REMO) which in turn would be used as input for the WetSpa model for future water resources simulation based on A1B and B1 special report for emission scenarios (SRES). Simulations of the SDSM and WetSpa models showed that rainfall will be increased by 24% under A1B and 25.3% under B1. The minimum and maximum temperatures will also increment by 0.17 and 0.09 °C, respectively, under A1B and by 0.16 and 0.07 °C under B1, respectively. Similarly, for A1B and B1, positive changes are likely to occur for baseflow by 14% and 8%, respectively, for recharge by 5% and 2%, respectively, and for evapotranspiration by 15% and 18%, respectively. However, the surface runoff would decrease by 13% and 14%, respectively, under similar trends from the base period. This implies that a positive change is likely in the future water balance components of the watershed with the exception of runoff. As a result, increased exploitation of the water resources comparable to the resources increment is advised. However, optimized water resources allocation is worthwhile, providing it is in a sustainable way.