Multi-Scale Validation of Satellite-Based Precipitation Products and Their Impacts on Hydrological Simulation in a Humid Mountainous Basin

Accurate precipitation information is crucial for hydrological simulation and water resources management, especially in humid mountainous regions where complex terrain and spatially heterogeneous rainfall introduce considerable uncertainties. Satellite-based precipitation products provide important data sources for hydrological applications; however, their reliability and impacts on runoff simulations remain uncertain across different spatial and temporal scales. This study presents a multi-scale validation of four precipitation products, including GSMaP, PERSIANN, GPM IMERG, and CLDAS, and evaluates their effects on hydrological simulation in the Oujiang River Basin, a typical humid mountainous basin in southeastern China. Daily precipitation estimates from 2015 to 2020 were compared with gauge observations using statistical metrics and precipitation event indicators. The hydrological applicability of each product was further assessed by driving a semi-distributed Xin’anjiang model, with evaluations conducted at the basin outlet, seasonal periods, extreme rainfall events, and internal subbasins. Results showed that CLDAS achieved the best overall agreement with gauge observations, with lower systematic bias and higher capability in detecting precipitation variability. Satellite-only products exhibited larger uncertainties, particularly during extreme rainfall events and in areas with complex terrain. These precipitation uncertainties were further propagated into runoff simulations, leading to differences in hydrological performance among products. CLDAS-driven simulations showed the highest accuracy, achieving R2, NSE, and KGE values of 0.706, 0.681, and 0.815, respectively, which were comparable to simulations driven by gauge-based precipitation. Multi-scale analysis revealed that product performance varied among subbasins due to differences in topography, rainfall characteristics, and human regulation. This study demonstrates the importance of multi-scale validation for quantifying uncertainties in satellite-based precipitation products and improving their application in hydrological modeling over mountainous regions.