Evaluation of dams and weirs operating for water resource management of the Geum River

• We assessed the water supply capacity, energy generation and flow duration.
• We assessed the environmental management class of the changing riverine environment.
• We assessed to take countermeasures to mitigate resulting adverse environmental impacts.
• The presence of dam/weir controls optimizes the river flow for socioeconomic and the environment.

As part of the Four Major Rivers Restoration Project, 16 multi-functional weirs have recently been constructed in each river system in Korea. The Project has pursued ecological approaches through constructing artificial weirs in waterways to ensure sufficient flow even in the dry seasons, improving agricultural reservoirs to supply environmental flow for the rivers, and thereby enhancing the water quality of the rivers. However, these anthropogenic activities have been accompanying a significant change in the riverine environment. In this study, the SSARR (Streamflow Synthesis and Reservoir Regulation) model was used to estimate natural flow in the 14 sub-basins of the Geum River. The natural flow determined by the SSARR model was used in estimation of environmental flow and input data of reservoir operation model. Hec-ResSim was used to assess runoff variations, water supply and energy generation based on the protocols for the associated operation of dams and multi-functional weirs. In addition to this, a method developed by the IWMI (International Water Management Institute) was also used to analyze the environmental flow, considering channels, water fronts and flow variations, and thereby assess the environmental management class of changing the riverine environment and to take countermeasures to mitigate the resulting adverse environmental impacts. It is hoped that the results of this study will provide basic data to establish policies for the effective operation and management of the existing dams and the newly constructed multi-functional weirs, and the effective monitoring and preservation of aquatic ecosystems in the Geum River basin.