Linking Hydrodynamic Transport and Nutrient Fluxes to Land‐Use Patterns: A Predictive Framework for Soil Conservation in a Mountainous Catchment

ABSTRACT This study investigates the influence of land use on total suspended solids (TSS) flux and nutrient leaching within a mixed land‐use catchment. The primary objective was to enhance predictive accuracy for soil erosion and water quality by assessing hydrologic drivers critical for managing degradation risks. Our findings demonstrate a significant land‐use impact: stream reaches adjacent to arable land exhibited the highest concentrations of nitrate nitrogen (up to 6.25 mg dm −3 ) and phosphates (0.89 mg dm −3 ), whereas forests and permanent grasslands showed significantly lower levels. Arable lands also recorded the highest transport intensity (1.02 m 3 s −1 ), reflecting increased surface runoff and diminished water retention capacity compared to forested reaches (0.47 m 3 s −1 ). Furthermore, the complete transverse mixing distance, a proxy for natural purification efficiency, was longest in arable‐dominated reaches (52.26 m), contrasting with shorter distances in forests (35.26 m) and grasslands (31.21 m). Spatial autoregression (SAR) modeling identified significant correlations between phosphate levels and agricultural zones, as well as nitrate nitrogen and grasslands. These results underscore the necessity of integrating land‐use management into forest engineering and maintaining permanent riparian grasslands to optimize nutrient retention and sediment control in erosion‐prone regions.