Simulation of Runoff and Sediment Yield in Ungauged Small Watersheds Around the Henan Boundary Area of the Sanmenxia Reservoir

ABSTRACT Simulating hydrological and sediment conditions in data‐scarce regions is a key challenge in hydrology. This study focused on 14 data‐scarce tributaries in the Henan boundary area of the Sanmenxia Reservoir. Using methods like parameter transfer, coefficient of variation, and watershed similarity evaluation, we selected data‐rich reference watersheds and applied the Soil and Water Assessment Tool (SWAT) model to simulate runoff and sediment yield. Calibrated parameters were then transferred to the study watersheds. Results showed: (1) The Ba River and Hongnongjian River had a similarity of 0.89, while the Jian River and other small watersheds in the area had similarities between 0.75 and 0.95, indicating the Ba River and Jian River were suitable as reference watersheds. (2) The SWAT model simulated runoff and sediment yield for these watersheds from 1960 to 2022, with results calibrated and validated. (3) Transferred parameters were used to simulate runoff and sediment transport in each small watershed, yielding multi‐year averages with low errors (1.54% for runoff, 7.1% for sediment). These findings provide valuable references for managing small watersheds in the Sanmenxia Reservoir area.