Evaluation of vegetation-wetland-soil ecological water retention capacity in the source region of the Yangtze and Yellow rivers (SRYY)

• V-shaped ecological resilienceEcological water retention showed V-shaped recovery (2000–2020), driven by permafrost-wetland feedback. • Elevation-season patternsLow-altitude areas and summer seasons exhibited superior water retention, influenced by climate-vegetation interactions. • Soil-dominated regulationSoil contributed >45 % to water retention, surpassing wetland (>35 %) and vegetation systems (<15 %). • Vegetation synergy: Canopy-litter coupling enhanced seasonal retention (peak in July–August), correlating with NDVI dynamics. Ecological Regulation and Storage (ERS), a crucial natural regulatory mechanism in river basins, is vital in assessing watershed resilience and guiding water resource management. This study establishes a novel tripartite framework (vegetation-wetland-soil) to quantify ERS dynamics in the ecologically fragile Source Region of the Yangtze and Yellow Rivers (SRYY). Integrating multi-source hydrological data (2000–2020) with improved modeling approaches, including a modified SCS-CN method incorporating organic matter dynamics and NDVI-driven vegetation modules, we reveal three key insights: (1) Total ERS exhibited a distinct V-shaped trajectory during 2000–2020, underscoring the system’s resilience and recovery potential; (2) Wetland regulation dominated temporal fluctuations, followed by soil regulation, while canopy interception and litter retention functioned as stabilizing components; (3) Vegetation regulation displayed pronounced seasonal variability, with a robust positive correlation between canopy interception and litter retention (r = 0.94, p = 0.019), revealing synergistic hydrological coordination within the vegetation layer.