Hydrological evaluation of satellite and reanalysis-based rainfall estimates over the Upper Tekeze Basin, Ethiopia

Spatial rainfall data is an essential input to parametrically distributed hydrological models and is a main contributor to hydrological model uncertainty. Two important issues should be addressed before the use of satellite and reanalysis rainfall product at the basin level: (1) How useful are these rainfall estimates as forcing data for regional hydrological modelling? and (2) Which product should be selected at high-flow and low-flow conditions? This paper presents the hydrological performance of satellite and reanalysis rainfall products (CHIRPSv8 and EWEMBI) at three hydrological stations in the Upper Tekeze River Basin (UTB), northern Ethiopia. Results showed that the daily rainfall data from both CHIRPSv8 and EWEMBI are close to the rain gauge data, with relative errors 2.12 and 3.85%, respectively. The monthly stream-flow simulated by the Soil and Water Assessment Tool (SWAT) model driven by CHIRPSv8 and EWEMBI had a Kling-Gupta Efficiency of 0.6-0.79 and 0.58-0.64, respectively. The hydrological performance during high-flow seasons is superior to low-flow seasons for both CHIRPSv8 and EWEMBI. In particular, CHIRPSv8 showed a relatively better hydrological performance than EWEMBI. This study provides insights on the usefulness of gridded rainfall products for hydrological modelling and conditions under which they can be used over the UTB and other similar basins.