Performance evaluation of multiple satellite rainfall products for Dhidhessa River Basin (DRB), Ethiopia

Precipitation is a crucial driver of hydrological processes. Ironically, a reliable characterization of its spatiotemporal variability is challenging. Ground-based rainfall measurement using rain gauges is more accurate. However, installing a dense gauging network to capture rainfall variability can be impractical. Satellite-based rainfall estimates (SREs) could be good alternatives, especially for data-scarce basins like in Ethiopia. However, SRE rainfall is plagued with uncertainties arising from many sources. The objective of this study was to evaluate the performance of the latest versions of several SRE products (i.e., CHIRPS2, IMERG6, TAMSAT3 and 3B42/3) for the Dhidhessa River Basin (DRB). Both statistical and hydrological modeling approaches were used for the performance evaluation. The Soil and Water Analysis Tool (SWAT) was used for hydrological simulations. The results showed that whereas all four SRE products are promising to estimate and detect rainfall for the DRB, the CHIRPS2 dataset performed the best at annual, seasonal and monthly timescales. The hydrological simulation-based evaluation showed that SWAT's calibration results are sensitive to the rainfall dataset. The hydrological response of the basin is found to be dominated by the subsurface processes, primarily by the groundwater flux. Overall, the study showed that both CHIRPS2 and IMERG6 products could be reliable rainfall data sources for the hydrological analysis of the DRB. Moreover, the climatic season in the DRB influences rainfall and streamflow estimation. Such information is important for rainfall estimation algorithm developers.

Automated summary

Precipitation plays a vital role in hydrological processes and its spatiotemporal variability is difficult to characterize accurately. Ground-based rainfall measurement is more precise but installing a dense gauging network is impractical. Satellite-based rainfall estimates offer good alternatives, but come with uncertainties. This study evaluated the performance of various SRE products for the DRB, with CHIRPS2 showing the best results. Hydrological simulations revealed sensitivity to rainfall datasets and the dominance of subsurface processes in the basin, especially groundwater flux. CHIRPS2 and IMERG6 products are reliable data sources for hydrological analysis in the DRB, with climatic season affecting rainfall and streamflow estimation.