Quantifying vegetation canopy interception drivers and runoff effects using a coupled RS-Gash-WEP model

The canopy interception driving mechanism and its watershed-scale runoff influence are urgent research priorities. The WEP model was improved by coupling it with the RS-Gash canopy interception model and incorporating remote-sensing vegetation cover and leaf area index. The coupled model was applied to the upper Pihe River Basin, and structural equation modeling was used to identify interception drivers and runoff effects. Results showed the improved WEP model boosted simulation accuracy (NSE = 0.79, R 2 = 0.80), with the canopy retention module raising NSE by 0.07–0.17 in upstream and downstream regions. Canopy saturated rainfall (path coefficient=0.69), regulated by rainfall intensity, leaf area index, and vegetation cover, dominated interception; vegetation cover exerted weak direct effects (path coefficient=0.20). Enhanced interception reduced runoff intensity, mitigating hydrological cycles by decreasing surface runoff (impact coefficient=0.47). This study provided a scientific basis for revealing the regulatory mechanisms of canopy interception on watershed hydrological processes and improving watershed-scale hydrological modeling methods.