HGS RESEARCH HIGHLIGHT – Impact of Baseflow on Fish Community in the Ungcheon Stream, Korea
Choi, B., Oh, W. S., Kim, N. S., Cha, J. Y., & Lim, C. H. (2021). Impact of Baseflow on Fish Community in the Ungcheon Stream, Korea. PROCEEDINGS OF THE NATIONAL INSTITUTE OF ECOLOGY OF THE REPUBLIC OF KOREA, 2(4), 235–246. https://doi.org/10.22920/PNIE.2021.2.4.235
“The HydroGeoSphere (HGS) model was used to optimize baseflow from the seepage of groundwater into the river.”
Fig. 1. The study area.
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In this research highlight, researchers have explored how groundwater baseflow influences fish habitat in the Ungcheon stream, located downstream of the Boryeong Dam in Korea.
This investigation revealed five dominant fish species in the Ungcheon Stream, accounting for 75% of the total fish community: Zacco platypus, Zacco koreanus, Tridentiger brevispinis, Rhinogobius brunneus, and Pungtungia herzi, serving as focal species for the study. HydroGeoSphere (HGS) and River2D models were used in conducting hydrologic and hydraulic simulations, while a habitat suitability index model was employed to assess fish habitat.
By examining representative discharges with and without baseflow, the study observed a gradual increase in baseflow as the distance from the dam increased, significantly impacting the habitat suitability for the entire fish community. These findings highlight the role of baseflow in shaping physical habitat conditions in streams.
In light of historical perceptions of baseflow and surface water as isolated resources, this study emphasizes the interconnectedness of these elements in aquatic ecosystems. Understanding baseflow contributions to stream processes becomes pivotal for water policy and management decisions.
Traditionally, assessing baseflow relied on indirect methods, each with inherent assumptions. However, computational flow dynamics analysis emerges as a promising alternative, offering detailed insights into the hydrologic cycle.
Flow regulation by upstream impoundments can disrupt natural flow regimes, altering surface and subsurface waters and affecting downstream habitats. Despite the application of physical habitat simulations in various environmental contexts, the impact of baseflow on stream flow and aquatic ecosystems remains underexplored.
This research highlight fills this gap by investigating the influence of baseflow on fish habitats downstream of the Boryeong Dam, Korea. By integrating hydrological modelling, hydraulic simulations, and habitat suitability assessments, the research provides valuable insights into the intricate relationship between baseflow dynamics and aquatic ecosystem health.
Fig. 4. Distributions of water surface elevation and velocity; (a) Longitudinal distribution of the cross section-averaged water surface elevation, (b) Distribution of velocity.
Within the study, a HydroGeoSphere (HGS) model was used in optimizing baseflow from groundwater seepage into the river. By calculating baseflow within the study reach, HGS contributed to understanding how baseflow gradually increased with longitudinal distance, further illuminating its impact on fish habitat suitability.
Plain Language Summary:
In this study, researchers examined how baseflow affects the fish community in the Ungcheon stream in Korea. They found that five main fish species dominate this stream, making up 75% of the total fish population: Zacco platypus, Zacco koreanus, Tridentiger brevispinis, Rhinogobius brunneus, and Pungtungia herzi. Using HydroGeoSphere (HGS) and River2D models, the team simulated the hydrology and hydraulics of the stream. They also used a habitat suitability index model to predict fish habitat. By comparing discharge scenarios with and without baseflow, they discovered that baseflow gradually increased along the stream's length. Validating their hydraulic model, they confirmed that including baseflow led to a more accurate representation of water surface elevation. Analysis of composite suitability index distributions showed that baseflow significantly improved habitat suitability for the entire fish community. These findings emphasize the importance of considering baseflow in simulations of fish habitats, suggesting that it plays a crucial role in shaping the physical environment for aquatic life in streams.
Abstract:
This study investigated the impact of baseflow on fish community in the Ungcheon stream (16.5 km long) located downstream of the Boryeong Dam, Korea. Based on field monitoring, there were five dominant fish species in the Ungcheon Stream accounting for75% of the total fish community: Zacco platypus, Zacco koreanus, Tridentiger brevispinis, Rhinogobius brunneus, and Pungtungia herzi. These five fish species were selected as target species. HydroGeoSphere (HGS) and River2D models were used for hydrologic and hydraulic simulations, respectively. A habitat suitability index model was used to simulate fish habitat. To assess the impact of base-flow, each representative discharge was examined with or without baseflow. The HGS model was used to calculate baseflow within the study reach. This baseflow was observed to increase gradually with longitudinal distance. Validation of the hydraulic model demonstrated that computed water surface elevated when baseflow was included, which was in good agreement with measured data, as opposed to the result when baseflow was excluded. Composite suitability index distributions and weighted usable area in the study reach were presented for target species. Simulations indicated that the baseflow significantly increased habitat suitability for the entire fish community. These results demonstrate that there should be a substantial focus on the baseflow for physical habitat simulation.