Climatic, topographic, and groundwater controls on runoff response to precipitation: evidence from a large-sample data set

Runoff responses to precipitation can vary widely across catchments and climates, shaped by hillslope water storage and release dynamics and by the transmission of hydrological signals through channel networks. Understanding these controls is critical for interpreting hydrological behavior and informing water resource management.

Here, we apply ensemble rainfall–runoff analysis (ERRA) to characterize runoff responses across 189 Iranian catchments spanning diverse landscapes and climates. ERRA quantifies the increase in lagged streamflow attributable to each unit of additional precipitation while accounting for nonlinear catchment behavior.

Peak runoff response, as quantified by ERRA across Iran, is higher in more humid climates, in steeper and smaller catchments, and in catchments with shallower water tables. The direction and approximate magnitude of these effects persist after accounting for correlations among the drivers (e.g., deeper water tables are more common in more arid regions).

These findings highlight the importance of catchment attributes in shaping runoff behavior, particularly in arid and semi-arid regions, where climatic variability and groundwater dynamics play a crucial role in sustainable water resource management and effective flood risk mitigation.