Hydrological Evaluation of Satellite and Reanalysis-based Rainfall
Estimates Over the Upper Tekeze Basin, Ethiopia
Abstract
Spatial rainfall data is an essential input to physically based,
parametrically distributed hydrological models, and a main contributor
to hydrological model uncertainty. Two important issues should be
addressed before use of satellite and reanalysis rainfall product at
basin level: 1) how useful are these rainfall estimates as forcing data
for regional hydrological modeling? 2) which should be preferred for
hydrological modelling at high flow and low flow seasons? To this end,
rainfall estimates from a satellite-based product, CHIRPSv8, and
reanalysis data, EWEMBI, were used as input to SWAT model, and mode
performances were evaluated against streamflow measured at three gauge
stations in the Upper Tekeze River basin, northern Ethiopia for the
period of 2006-2015. Results showed that (I) the daily rainfall from
both CHIRPSv8 and EWEMBI are close to the rain gauge data, with relative
errors 2.12% and 3.85%, respectively; (II) the monthly streamflow
simulated by the SWAT model driven by the CHIRPSv8 and EWEMBI had a
Kling-Gupta Efficiency value of 0.6-0.79 and 0.58-0.64, respectively;
(III) the SWAT model calibrated with the CHIRPSv8 and EWEMBI rainfall
estimates has shown an improvement in hydrological performance compared
with that calibrated with interpolated ground observations; (IV) the
hydrological performance during high flow seasons is superior to low
flow seasons for both CHIRPSv8 and EWEMBI, thus promoting the use of the
products for applications focusing on the high flow conditions. In
particular, CHIRPSv8 showed relatively better hydrologic performance
than EWEMBI. This study provides insight on the usefulness of the
gridded rainfall products for hydrological modeling and under which
conditions they can be used to generate a plausible level of adequacy
and reliability over the Upper Tekeze River basin.