Spatiotemporal Variability of Runoff Coefficients and Rainfall–Runoff Responses in a Mountainous Basin Using Integrated Hydrological Analogy and SCS–CN Models
摘要
Urbanization and climate change have substantially altered rainfall–runoff processes, intensifying seasonal hydrological imbalances in mountainous basins. While widely used models such as hydrological analogy, the SCS-CN method, and reciprocal formulations are individually established, their systematic integration for mechanism-oriented runoff analysis remains limited. In this study, a structured three-stage coupling framework was developed in the Feng gao River basin (Southwest China) to quantify spatiotemporal variability of runoff coefficients (RCs) and to diagnose rainfall–runoff mechanisms across land-use types. First, regionalized runoff scaling based on hydrological analogy provided basin-level runoff constraints under ungauged conditions. Second, these constraints were used to calibrate SCS–CN parameters, reducing seasonal bias in conventional applications. Third, a reciprocal diagnostic model was introduced to characterize nonlinear rainfall–RC relationships and to extract physically interpretable parameters representing structural runoff ceilings (1/a) and rainfall sensitivity (b). Results show strong consistency between the calibrated SCS-CN outputs and regionalized runoff estimates (r = 0.9732), while revealing systematic seasonal contrasts between dry and wet periods. Land-use heterogeneity exerted pronounced control on runoff generation: water bodies (84.37%) and transportation land (67.69%) exhibited high and stable RCs, cropland (34.40%) and built-up land (32.50%) showed transitional responses, whereas forest (22.39%), grassland (25.53%), and shrubland (16.63%) functioned as hydrological buffers. The reciprocal model successfully captured nonlinear rainfall–runoff dynamics across all land-use categories (R² > 0.85), enabling explicit linkage between land-use structure and runoff sensitivity. By bridging empirical regional scaling with process-based calibration and parameter-diagnostic modeling, this study advances a transferable framework for runoff estimation in data-scarce mountainous basins. The integration strategy enhances both predictive reliability and mechanistic interpretability, providing practical support for watershed management under accelerating urbanization and climate variability.