• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.2
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• pp.194-207
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• 2021

It is necessary to assess and manage the different elements of the marine ecosystem, such as climate change, habitat, primary and secondary production, energy flow, food web, potential yield, and fishing, to maintain the health of the ecosystem as well as support sustainable development of fishery. We set up an ecosystem model around the Korean peninsula to produce scientific predictions necessary for the assessment and management of marine ecosystems and presented the usability of the model with scenario experiments. We used the Atlantis ecosystem model based on the marine food web; Atlantis is a three-dimensional end-to-end model that includes the information and processes within an entire system, from an abiotic environment to human activity. We input the ecological and biological parameters, such as growth, mortality, spawning, recruitment, and migration, to the Atlantis model via functional groups using existing research and local measurements. During the simulation period (2018-2019), we confirmed that the model reproduced the observed data reasonably and reflected the actual ecosystem characteristics appropriately. We thus identified the usability of a marine ecosystem model with experiments on different environmental change scenarios.

• Journal of Korean Society on Water Environment
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• v.36 no.6
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• pp.636-650
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• 2020

A modeling system that can consider the overall water environment and be used to integrate hydrology, water quality, and aquatic ecosystem on a watershed scale is essential to support decision-making in integrated water resources management (IWRM). In adapting imported models for evaluating the unique water environment in Korea, a platform perspective is becoming increasingly important. In this study, a modeling platform is defined as an ecosystem that continuously grows and provides sustainable values through voluntary participation- and interaction-of all stakeholders- not only experts related to model development, but also model users and decision-makers. We assessed the conceptual values provided by the IWRM modeling platform in terms of openness, transparency, scalability, and sustainability. I We also reviewed the technical aspects of functional and spatial integrations in terms of socio-economic factors and user-centered multi-scale climate-forecast information. Based on those conceptual and technical aspects, we evaluated potential modeling platforms such as Source, FREEWAT, Object Modeling System (OMS), OpenMI, Community Surface-Dynamics Modeling System (CSDMS), and HydroShare. Among them, CSDMS most closely approached the values suggested in model development and offered a basic standard for easy integration of existing models using different program languages. HydroShare showed potential for sharing modeling results with the transparency expected by model user-s. Therefore, we believe that can be used as a reference in development of a modeling platform appropriate for managing the unique integrated water environment in Korea.

• Journal of Korean Society on Water Environment
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• v.36 no.6
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• pp.592-610
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• 2020

In South Korea, the concept of water environment was expanded to include aquatic ecosystems with the Integrated Water Management implementation. Watershed-scale modeling is typically performed for hydrologic component analysis, however, there is a need to expand to include ecosystem variability such that the modeling corresponds to the social and political issues around the water environment. For this to be viable, the modeling must account for several distinct features in South Korean watersheds. The modeling must provide reasonable estimations for peak flow rate and apply to paddy areas as they represent 11% of land use area and greatly influence groundwater levels during irrigation. These facts indicate that the modeling time intervals should be sub-daily and the hydrologic model must have sufficient power to process surface flow, subsurface flow, and baseflow. Thus, the features required for watershed-scale modeling are suggested in this study by way of review of frequently used hydrologic models including: Agricultural Policy/Environmental eXtender(APEX), Catchment hydrologic cycle analysis tool(CAT), Hydrological Simulation Program-FORTRAN(HSPF), Spatio-Temporal River-basin Ecohydrology Analysis Model(STREAM), and Soil and Water Assessment Tool(SWAT).

• Journal of Ecology and Environment
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• v.43 no.1
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• pp.14-21
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• 2019

Background: Stoichiometry plays an important role in understanding nutrient composition and cycling processes in aquatic ecosystems. Previous studies have considered C:N:P ratios constant for both DOM (dissolved organic matter) and POM (particulate organic matter). In this study, water samples were collected in the six major rivers in Korea and were incubated for 20 days. C:N:P ratios were determined during the time course of the incubations. This allowed us to examine the changes in N and P contents of organic matter during decomposition. Results: POM and DOM showed significant differences in N and P content and the elemental ratios changed during the course of decomposition; DOM showed higher C:N and C:P ratios than POM, and the C:N and C:P ratios increased during decomposition, indicating the preferential mineralization of P over N and N over C. Conclusions: The N and P contents of organic matter in aquatic ecosystem are far from constant and vary significantly during decomposition. More detailed information on the changes in C:N:P ratios will provide improved understanding of decomposition processes and improved modeling of aquatic ecosystems.

• Journal of Korean Society on Water Environment
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• v.36 no.6
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• pp.621-635
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• 2020

Water quality models are scientific tools that simulate and interpret the relationship between physical, chemical and biological reactions to external pollutant loads in water systems. They are actively used as a key technology in environmental water management. With recent advances in computational power, water quality modeling technology has evolved into a coupled three-dimensional modeling of hydrodynamics, water quality, and ecological inputs. However, there is uncertainty in the simulated results due to the increasing model complexity, knowledge gaps in simulating complex aquatic ecosystem, and the distrust of stakeholders due to nontransparent modeling processes. These issues have become difficult obstacles for the practical use of water quality models in the water management decision process. The objectives of this paper were to review the theoretical background, needs, and development status of water quality modeling technology. Additionally, we present the potential future directions of water quality modeling technology as a scientific tool for national environmental water management. The main development directions can be summarized as follows: quantification of parameter sensitivities and model uncertainty, acquisition and use of high frequency and high resolution data based on IoT sensor technology, conjunctive use of mechanistic models and data-driven models, and securing transparency in the water quality modeling process. These advances in the field of water quality modeling warrant joint research with modeling experts, statisticians, and ecologists, combined with active communication between policy makers and stakeholders.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.4
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• pp.386-394
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• 2002

Carrying capacity model focused on interactions between the filter-feeder growth and their environments is presented, and differences among existing various carrying capacity models are reviewed. For carrying capacity modeling of shellfish system, we constructed a new numerical model coupled oyster growth model with an ecosystem model (EUTRP2). Physical and biological processes such as water transport and mixing, primary production, feeding and growth of the cultivated oyster, Crassostrea gigas and benthic-pelagic exchange were included in the model, Simulated results for validation showed that the more phytoplankton biomass decreased, the more oyster meat weight and nutrients increased, suggesting a powerful tool for reasonable management of shellfish aquaculture. The model was sensitive to parameters controlling the primary production. Among the ecosystem compartments, the oyster growth is highly influenced by small changes in the physiological parameters of phytoplankton and oyster. This sensitivity analysis indicated the importance of experimental data on biological parameters for calibration of the model.

• Water Engineering Research
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• v.7 no.1
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• pp.29-41
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• 2006

The Imha watershed is vulnerable to severe erosion due to the topographical characteristics such as mountainous steep slopes. Sediment inflow from upland area has also deteriorated the water quality and caused negative effects on the aquatic ecosystem of the Imha reservoir. The Imha reservoir was affected by sediment-laden density currents during the typhoon 'Maemi' in 2003. The RUSLE model was combined with GIS techniques to analyze the mean annual erosion losses and the soil losses caused by typhoon 'Maemi'. The model is used to evaluate the spatial distribution of soil loss rates under different land uses. The mean annual soil loss rate and soil losses caused by typhoon 'Maemi' were predicted as 3,450 tons/km2/year and 2,920 ton/km2/'Maemi', respectively. The sediment delivery ratio was determined to be about 25% from the mean annual soil loss rate and the surveyed sediment deposits in the Imha reservoir in 1997. The trap efficiency of the Imha reservoir was calculated using the methods of Julien, Brown, Brune, and Churchill and ranges from 96% to 99%.

• Ecology and Resilient Infrastructure
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• v.2 no.3
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• pp.198-205
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• 2015

Impacts of climate change on aquatic ecosystems range from changes in physiological processes of aquatic organisms to species distribution. In this study, MaxEnt that has high prediction power without nonoccurrence data was used to simulate fish distribution changes in the Geum river watershed according to climate change. The fish distribution in 2050 and 2100 was predicted with RCP 8.5 climate change scenario using fish occurrence data (a total of 47 species, including 17 endemic species) from 2007 to 2009 at 134 survey points and 9 environmental variables (monthly lowest, highest and average air temperature, monthly precipitation, monthly lowest, highest and average water temperature, altitude and slope). The fitness of MaxEnt modeling was successful with the area under the relative operating characteristic curve (AUC) of 0.798, and environmental variables that showed a high level of prediction were as follows: altitude, monthly average precipitation and monthly lowest water temperature. As climate change proceeds until 2100, the probability of occurrence for Odontobutis interrupta and Acheilognathus yamatsuatea (endemic species) decreases whereas the probability of occurrence for Microphysogobio yaluensis and Lepomis macrochirus (exotic species) increases. In particular, five fish species (Gnathopogon strigatus, Misgurnus mizolepis, Erythroculter erythropterus, A. yamatsuatea and A. koreensis) were expected to become extinct in the Geum river watershed in 2100. In addition, the species rich area was expected to move to the northern part of the Geum river watershed. These findings suggest that water temperature increase caused by climate change may disturb the aquatic ecosystem of Geum river watershed significantly.

• Journal of Korea Water Resources Association
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• v.54 no.9
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• pp.719-730
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• 2021

The objective of this study is to develop the water quality and aquatic ecosystem model for Andong lake using SWAT-WET (Soil and Water Assessment Tool-Water Ecosystem Tool) and to evaluate the applicability of WET. To quantify the pollutants load flowing into Andong lake, a watershed model of SWAT was constructed for Andong Dam basin (1,584 km²). The calibration results for Dam inflow and water quality loads (SS, T-N, T-P) were analyzed that average R² was more than 0.76, 0.69, 0.84, and 0.60 respectively. The calibrated SWAT results of streamflow and nutrients concentration was used into WET input data. WET was calibrated and validated for water temperature, dissolved oxygen, and water quality concentration (T-N, T-P) of Andong lake. The WET calibrated results was analyzed that PBIAS was +19%, -13%, +4%, and +26.5% respectively and showed that it was simulated to a significant level compared with the observation data. The observed dry weight (gDW/m²) of zoobenthos was less than 0.5, but the average value of simulation was analyzed to be 0.8, which is because the WET model considers zoobenthos with a broader concept. Although accurate calibration is difficult due to the lack of observed data, SWAT-WET can analyze the effects of environmental change in the upstream watershed on the lake based on long-term simulation based on watershed model. Therefore, the results of this study can be used as basic data for managing the aquatic environment of Andong lake.

• Journal of Ecology and Environment
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• v.36 no.1
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• pp.73-83
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• 2013

The object of this study was to evaluate lotic ecosystem health using multiple eco-metric approaches such as water chemistry diagnosis, physical habitat health evaluations, and biological integrity modeling at 100 streams of four major watersheds. For the study, eight chemical water quality parameters such as nutrients (N, P) and organic material were measured and 11-metric models of Qualitative Habitat Evaluation Index (QHEI) and multiple eco-metric health assessment model (MEHA) were applied to the four major watershed. Nutrient analysis of nitrogen (N) and phosphorus (P) in all watersheds indicated a eutrophic state depending on the locations of sampling streams. Physical habitat health, based on the QHEI model, averaged 114 (range: 56 - 194), judging as a "good condition" by the criteria of Plafkin et al. (1989). In addition, primary (H1 - H4), secondary (H5 - H7), and tertiary habitat metric variables (H8 - H11) were analyzed in relation to the physical habitat degradations. The plots of tolerant species ($P_{TS}$) and sensitive species ($P_{SS}$) to water quality showed that the proportions of $P_{TS}$ had positive linear functions with nutrients, and that the $P_{SS}$ had inverse linear relations with the chemical variables. The model of eco-metric health assessment showed that mean MEHA was 20.4, indicating a fair condition. Overall, our data suggest that water chemistry, based on nutrients and organic matter, directly modified the trophic structures in relation to food chain in the aquatic ecosystems, and then these directly influenced the compositions of tolerance/sensitive species, resulting in degradations of overall ecological health.