A New Process‐Based Approach for Evaluating Gridded Precipitation Products in Mountain Watersheds: Test Cases From the Central Andes of Argentina

Abstract

Adequate quantification of precipitation and its spatiotemporal variability is crucial for understanding the physical and biological processes within a watershed. Mountain watersheds pose particular challenges due to strong spatial heterogeneity in precipitation and typically sparse in situ monitoring networks. The increasing availability of gridded precipitation products can help address these limitations, but their reliability at local or sub-regional scales remains difficult to assess. This study proposes a novel, process-based approach that incorporates daily streamflow data to evaluate the performance of four widely used gridded precipitation datasets (CHIRPS-v2, MSWEP-v2.8, GPCC-v2022 and TerraClimate). Five key watersheds in central-western Argentina (ca. 30°–37° S) serve as case studies. The evaluation framework is based on five process-informed expectations derived from the region's climate and topography: (a) most annual precipitation should fall as snow during winter (April–September); (b) a strong positive relationship should exist between winter precipitation and summer streamflow; (c) interannual variability of precipitation should exceed that of streamflow due to basin-scale damping effects; (d) runoff coefficients should be statistically lower than unity, reflecting mass conservation; and (e) winter precipitation should be concentrated at higher elevations. We apply simple non-parametric statistical tests to evaluate how well each dataset meets these expectations. A comparative assessment identifies the most reliable product for each watershed. Our findings show that MSWEP and TerraClimate perform best overall, particularly in capturing total precipitation and its seasonality. Other datasets fail to reproduce key hydrological signals, likely due to a lack of physically based inputs (e.g., reanalysis). Overall, this process-based, catchment-integrative evaluation offers a promising framework for assessing precipitation products in other snow-dominated mountain regions with limited ground observations, provided that the dominant hydroclimatic processes are well understood.