Multi-Site Calibration of Hydrological Model and Spatio-Temporal Assessment of Water Balance in a Monsoon Watershed

Understanding hydrological processes using hydrological model parameters can improve the management of water resources in a watershed. This research uses the Soil and Water Assessment Tool (SWAT) model in examining the water balance in the Yeongsan River Basin, South Korea. Summer monsoon dominates the region, accounting for about 60–70% of the rain between June to September. The basin is facing significant challenges in water management due to the limited availability of water and the high demand for agricultural water due to the construction of two weirs on the river. To this end, a new multi-site calibration approach-based SWAT hydrological model that can accurately reproduce the hydrological trend and average discharges of the Yeongsan basin for 42 years (1980–2021) was developed. Some statistical matrices (such as Nash–Sutcliffe model efficiency) were utilized in calibrating and validating the model. Results show that the performance indicators for the four investigated stream flow stations were satisfactory. In addition, the water balance study revealed that the highest precipitation and evapotranspiration occurred in August, whereas the highest water yield, lateral flow, and surface flow occurred in July. Further, the model revealed that the Yeongsan river basin receives the majority of its water from the rains during the monsoon season. The model developed in this study can aid planners in managing water resources in the Yeongsan river basin.