• Journal of Korea Water Resources Association
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• v.47 no.6
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• pp.547-559
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• 2014

The objective of this study is to evaluate the performance of the complementary relationship-based evapotranspiration models, namely, advection-aridity (AA) model of Brutsaert and Stricker and the CRAE model of Morton for estimating actual evapotranspiration. Both models were applied to the Bokhacheon middle-upper watershed, and their estimates were evaluated against the water balance estimate. The calculation was made on a daily basis and comparison was made on monthly and annual bases. For comparison, the water balance estimates were not obtained from the observed precipitation and streamflow data but were based on the simulated data by using integrated watershed model, SWAT-K which is the revised version of SWAT. The reason not to directly use the observed data for water balance estimate is that the credible record period is not sufficient and the streamflow has been altered due to water use and release. Overall, the results showed that both AA model and CRAE model with their original parameters overestimate annual and monthly evapotranspiration, and the large difference between the complementary relationship-based approach and the water balance approach occurs especially for the dry season from Nov. to Mar. It was found out that the parameters, particularly for the advection related parameter, must be recalibrated to accurately produce monthly and annual regional evapotranspiration for this study area.

• Journal of Korea Water Resources Association
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• v.47 no.12
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• pp.1121-1134
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• 2014

The distributed watershed model of rainfall-runoff-soil erosion-sedimen transport was constructed for the Naesung Stream Watershed with high potentiality and risk of sediments produced by soil erosion. The sensitivity analyses of roughness coefficient and hydraulic conductivity which affected the modeling results of runoff and sediment concentration were performed in this study. As a result, the change of the roughness coefficient for the forest area from 0.4 to 0.45 did not affect the change in runoff and stream discharge and the average value and range of sediment concentration were also insignificantly increased with few difference. As a result of the sensitivity analysis of the hydraulic conductivity, the total amount of runoff and maximum runoff were gradually increased as the hydraulic conductivity was reduced. In the case of sediment concentration modeling, the average and the range of sediment concentration for all stations were increased as the hydraulic conductivity was decreased. For the Hyangseok Station, in case of the hydraulic conductivity reduced by 50%, the simulation result of sediment concentration was most similar to the estimated value by the sediment rating curve.

• Korean Journal of Ecology and Environment
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• v.50 no.4
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• pp.403-410
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• 2017

We collected fishes at the 12,873 sites in stream order (1~7) from 2008 to 2016. In the results, two populations(Zacco platypus and Zacco koreanus) represented distributional differences in the stream order gradient, and correlation analysis showed that the two populations had a potential competitive relationship. The ecological characteristics of the fish except for the Z. platypus and the Z. koreanus, according to the gradient of stream order showed a pronounced gradient in the species such as intermediate species, sensitive species, carnivores, herbivores and omnivores. The two populations showed a high correlation between intermediate species, sensitive species of the tolerance guild and omnivores, insectivores of the trophic guild. Fish assessment index (FAI) was negative relation with stream order. According to the stream order gradient, the two populations showed different correlations with FAI.

• Journal of Korea Water Resources Association
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• v.54 no.9
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• pp.681-692
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• 2021

Vegetation processes have a significant impact on rainfall runoff processes through evapotranspiration control, but are rarely considered in the conceptual lumped hydrological model. This study evaluated the model performance of the Hapcheon Dam watershed by integrating the ecological module expressing the leaf area index data sensed remotely from the satellite into the hydrological partition module. The proposed eco-hydrological model has three main features to better represent the eco-hydrological process in humid regions. 1) The growth rate of vegetation is constrained by water shortage stress in the watershed. 2) The maximum growth of vegetation is limited by the energy of the watershed climate. 3) The interaction of vegetation and aquifers is reflected. The proposed model simultaneously simulates hydrologic components and vegetation dynamics of watershed scale. The following findings were found from the validation results using the model parameters estimated by the SCEM algorithm. 1) Estimating the parameters of the eco-hydrological model using the leaf area index and streamflow data can predict the streamflow with similar accuracy and robustness to the hydrological model without the ecological module. 2) Using the remotely sensed leaf area index without filtering as input data is not helpful in estimating streamflow. 3) The integrated eco-hydrological model can provide an excellent estimate of the seasonal variability of the leaf area index.

• Journal of Wetlands Research
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• v.24 no.1
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• pp.25-37
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• 2022

Climate change is becoming increasingly unpredictable. This has led to changes in various systems such as ecosystems, human life and hydrological cycles. In particular, the recent unpredictable climate change frequently causes extreme droughts and torrential rains, resulting in complex water resources disasters that cause water pollution due to inundation and retirement rather than primary disasters. SWAT was used as a watershed model to analyze future runoff and pollutant loads. The climate scenario analyzed the RCP4.5 climate scenario of the Meteorological Agency standard scenario (HadGEM3-RA) using the normal quantitative mapping method. Runoff and pollutant load analysis were performed by linkage simulation of climate scenario and watershed model. Finally, the results of application and verification of linkage model and analysis of future water quality change due to climate change were presented. In this study, we simulated climate change scenarios using artificial neural networks, analyzed changes in water temperature and turbidity, and compared the results of dams with artificial neural network results through W2 model, a reservoir water quality model. The results of this study suggest the possibility of applying the nonlinearity and simplicity of neural network model to Hapcheon dam water quality prediction using climate change.

• Journal of Korean Society on Water Environment
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• v.36 no.5
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• pp.385-391
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• 2020

Soil loss is a serious problem frequently caused by local torrential rainfalls due to climate change. In particular, soil loss is occurring in agricultural areas rather than urban areas, and many pollutants are introduced into rivers, causing environmental problems. To reduce soil loss, the Ministry of Environment has designated and managed non-point source management areas. The Jaun-district in Hongcheon-gun, which was designed as a non-point pollution source management area in Gangwon-do, is located in the upper stream of Soyang Lake. Most of the agricultural fields are composed of highland agriculture fields. The highland agricultural fields in the Jaun-district are also composed of large-scale farming areas, and the ditches located near the agricultural fields have been illegally used for farmland. Therefore, the local government in Hongcheon-gun is conducting a project to restore the ditches occupied by agricultural fields. However, an analysis of the amount of soil loss that can be reduced by the restoration of the ditches has not been conducted yet. Thus, the purpose of this study was to analyze the effect of reducing the soil loss from the restoration of the ditches used as agricultural fields in the Jaun-district. The SATEEC L Module was used to analyze the reduction in soil loss by ditch restoration. The SATEEC L Module was constructed to estimate the LS factor using Moore and Burch's method after calculating the slope length using the digital elevation model and the maximum allowable slope length. The LS factor and the USLE formula were used to estimate the amount of soil loss that could be reduced by ditch restoration. The analysis showed that the ditch restoration could reduce about 16.6% of the soil loss in the Jaun-district. The results of this study will contribute to the study of methods to reduce soil loss in non-point pollution management areas.

• Korean Journal of Remote Sensing
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• v.38 no.6_3
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• pp.1777-1788
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• 2022

The reservoir is a major water supply source in the domestic agricultural environment, and the monitoring of water storage of reservoirs is important for the utilization and management of agricultural water resource. Remote sensing via satellite imagery can be an effective method for regular monitoring of widely distributed objects such as reservoirs, and in this study, image classification and image segmentation algorithms are applied to Sentinel-1 Synthetic Aperture Radar (SAR) imagery for water body detection in 53 reservoirs in South Korea. Six algorithms are used: Neural Network (NN), Support Vector Machine (SVM), Random Forest (RF), Otsu, Watershed (WS), and Chan-Vese (CV), and the results of water body detection are evaluated with in-situ images taken by drones. The correlations between the in-situ water surface area and detected water surface area from each algorithm are NN 0.9941, SVM 0.9942, RF 0.9940, Otsu 0.9922, WS 0.9709, and CV 0.9736, and the larger the scale of reservoir, the higher the linear correlation was. WS showed low recall due to the undetected water bodies, and NN, SVM, and RF showed low precision due to over-detection. For water body detection through SAR imagery, we found that aquatic plants and artificial structures can be the error factors causing undetection of water body.

• Journal of Korean Society on Water Environment
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• v.39 no.2
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• pp.142-152
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• 2023

Infiltration is a process by which precipitation infuses into subsurface soils. The process determines the surface flow and baseflow volume, and it is one of most important hydrological processes regarding nonpoint source pollution management. Therefore, the Ministry of Environment has developed a guideline to determine the impervious area ratio to understand the hydrological process in administrative districts and watersheds. The impervious area ratio can be determined using land use or land cover maps. Three approaches were explored to determine the impervious area ratio in 25 districts in Seoul. The impervious area ratio was determined by employing the Land registration map and Land property data in the first approach, Land property map in the second approach, and Land cover map in the third approach. The ratio ranged from 38.96% to 83.01% in the first approach, 38.98% to 83.02% in the second approach, and 37.62% to 76.63% in the third approach. Although the ranges did not provide any significant differences in the approaches, some districts displayed differences up to 9.48% by the approach. These differences resulted from the fact that the data were land use or land cover, especially in the area of airport, residential complex area, and school sites. In other words, division of the pervious and impervious areas in an individual plot was not allowed in the Land registration map, while it was allowed in the Land cover map. Therefore, it was concluded that there is a need to revise the guideline so that a reasonable impervious area ratio can be determined in the districts.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.10 no.1
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• pp.36-43
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• 2007

This study was carried out to know how erosion control function of forests varies as forests develop in watersheds. The erosion control function among the forest welfare functions can be estimated by comparing sediment yield in stocked with non-stocked area. Sediment yield of reservoirs in stocked area were collected from farmland improvement associations. The sediment yields in non-stocked area were using USLE (Universal Soil Loss Equation) in the same reservoirs. Forests' erosion control function estimated by differences of the sediment yield between stocked and non-stocked area was static model because of no consideration on forest aging. Dynamic model was developed to consider a forest stand age. The model comprises the relationship between average forest age in watershed and sediment yield. The amount of sediment yield was different depending mother rocks. It decreased exponentially according to the forest's grow up. In case of igneous rock, the volume of sediment yield $Y_{ig}=1.4431e\;^{0.023x}$(x=average forest age), metamorphic rock $Y_{me}=4.7115e\;^{0.0694x}$, and sedimentary rock $Y_{se}=1.2808e\;^{0.028x}$.

• Journal of Korean Society on Water Environment
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• v.28 no.3
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• pp.426-435
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• 2012

The variation of stream flow is the one of the most important factors which influence on that of water quality in the unit watershed. The target water quality goal is established and permissible load is allotted in the base of the standard flow condition along with its water quality for the management of Total Maximum Daily Loads (TMDLs). A standard flow selected could cause problems in the load allotment if it was not properly arranged. This study reviewed the acquisition of water quality data, the self-variation and the retainability in water quality on the specific flow conditions. This study also proposed the median and the adjusted average flow condition out of general flow conditions as alternative standard flow conditions. It is considered that the alternatives can make the water quality data easily acquired and the water quality representativeness more enhanced on the standard flow conditions.