Author(s): Joo-Heon Lee; Jong-Suk Kim; Seo-Yeon Park; Young-Jun Kim

Linked Author(s): Joo-Heon Lee

Keywords: Drought; Ecosystem; HEC-EFM

Abstract: Drought is traditionally classified into meteorological drought, agricultural drought, and hydrological drought, and is monitored and managed. However, the damage caused by water shortage due to prolonged drought is not limited to human activities, but also causes serious damage to the ecosystem and the environment. Recently, studies for monitoring and evaluating environmental or ecological drought have been actively conducted. In this study, an environmental drought monitoring method was developed in the river ecosystem considering the fish habitat, and the role of the dam on the restoration of the river aquatic ecosystem and environmental drought management is analyzed. To analyze the flow regime, fish habitat, and environmental flow change before and after dam construction, a multidisciplinary approach linking ecology, hydrology, hydraulics and GIS was applied. A two-dimensional hydrodynamic habitat simulation model was applied to estimate the ecological flow required to secure habitats for each target fish species in the Gam river in Korea. HEC-EFM (Ecosystem Function Model), HEC-RAS (River Analysis System), Geo-EFM, Geo-Ras was operated in conjunction to quantitatively evaluate environmental flow and fish habitat changes required for river ecosystems. EcoDI_FH(Ecological Drought Index for Fish Habitat) was developed using the results of calculating the ecological flow required to secure the habitat of the target fish species. As a result of comparing SPI, which is a meteorological drought index calculated by applying precipitation from the Gam river basin, and EcoDI_FH based on fish habitat, the severity of ecological drought was similar in the meteorological drought period (2008-2009) before dam construction. However, after the dam construction, it was found that the ecological drought situation was maintained for a considerable period of time due to the supply of environmental flow from the dam even during the meteorological drought period (2014-2015). By applying HEC-EFM and Geo-EFM, the effect of the Buhang Dam, built in 2013 in the Gam river basin, on changes in the environmental flow required for various ecosystems including downstream vegetation, benthic organisms, and fish was analyzed. It was analyzed that both positive and negative changes were brought about for each type of ecosystem and for each required period of environmental flow. The negative impact of dam construction on the disconnection of habitat connectivity cannot be ignored. Nevertheless, sophisticated dam operation for the river environment was expected to be the most efficient alternative to the restoration of the damaged ecosystem and the restoration of the natural flow regime. It is judged that real-time monitoring of ecological drought is possible by using the EcoDI_FH proposed in this study, and it is expected that the dam operation method during the drought period to respond appropriately to environmental drought can be technically presented.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022948

Year: 2022