Changes in Groundwater and Surface Water Interactions due to Weir Operation in the Nakdonggang River Basin, Korea, Using an Integrated Hydrological Model

Hydraulic structures affect rive environment, leading to changes in groundwater and surface water interactions. In South Korea, 8 weirs were installed in Nakdonggang River, in 2012, to secure sufficient water resources. This study aims to analyze the impacts of weir operation on the integrated water environment in the Nakdonggang River basin, South Korea. A basin-scale hydrological model for Nakdonggang River basin was developed to simulate the groundwater and surface water dynamics using HydroGeoSphere, three-dimensional fully integrated surface-subsurface hydrological model. Our results showed that the overall fluctuations in river flow decreased, while the river temperature increased during weir operation. In addition, groundwater delays hydrological responses within the integrated water environment of the study area and, in particular, plays a critical role in mitigating seasonal fluctuations in surface water flow. This study highlights the importance of integrated groundwater and surface water management to sustain the health of the integrated water environment, address future climate change, and reduce vulnerability to anthropogenic environmental changes and climatic variability.