• Journal of Soil and Groundwater Environment
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• v.28 no.6
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• pp.71-89
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• 2023

A groundwater potential map (GPM) was built for the Nakdonggang River Basin based on ten variables, including hydrogeologic unit, fault-line density, depth to groundwater, distance to surface water, lineament density, slope, stream drainage density, soil drainage, land cover, and annual rainfall. To integrate the thematic layers for GPM, the criteria were first weighted using the Analytic Hierarchical Process (AHP) and then overlaid using the Technique for Ordering Preferences by Similarity to Ideal Solution (TOPSIS) model. Finally, the groundwater potential was categorized into five classes (very high (VH), high (H), moderate (M), low (L), very low (VL)) and verified by examining the specific capacity of individual wells on each class. The wells in the area categorized as VH showed the highest median specific capacity (5.2 m³/day/m), while the wells with specific capacity < 1.39 m³/day/m were distributed in the areas categorized as L or VL. The accuracy of GPM generated in the work looked acceptable, although the specific capacity data were not enough to verify GPM in the studied large watershed. To create GPMs for the determination of high-yield well locations, the resolution and reliability of thematic maps should be improved. Criterion values for groundwater potential should be established when machine learning or statistical models are used in the GPM evaluation process.

• Journal of Korea Water Resources Association
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• v.57 no.7
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• pp.471-479
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• 2024

Flood damage is becoming more serious due to the heavy rainfall caused by climate change. Physically based hydrological models have been utilized to predict stream water level variability and provide flood forecasting. Recently, hydrological simulations using machine learning and deep learning algorithms based on nonlinear relationships between hydrological data have been getting attention. In this study, the Long Short-Term Memory (LSTM) algorithm is used to predict the water level of the Seomjin River watershed. In addition, Climate Prediction Center morphing method (CMORPH)-based gridded precipitation data is applied as input data for the algorithm to overcome for the limitations of ground data. The water level prediction results of the LSTM algorithm coupling with the CMORPH data showed that the mean CC was 0.98, RMSE was 0.07 m, and NSE was 0.97. It is expected that deep learning and remote data can be used together to overcome for the shortcomings of ground observation data and to obtain reliable prediction results.

• Journal of the Korean Association of Geographic Information Studies
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• v.8 no.3
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• pp.74-83
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• 2005

The Riparian Buffer Zone has many potential values including the preservation of water quality as well as being ecologically friendly. This study aims to quantitatively analyze the landscape structure index of the Riparian Buffer Zone in the Kyoung-an stream and to produce base information necessary for proper management. The study used aerial images that were applied to geometric corrections for a time series from 1966 to 2000 for land data and also used FRAGSTATS, which is a type of ARCVIEW extension module, as an analysis tool. An analysis of land use change and the Landscape Index revealed that the area of farm land has decreased and that the area of residential property has increased. In addition, there was a slight change for land used for purposes other than farming or for residence. The results of analyzing the Landscape Structure Index, revealed that the NP has increased from 437 in 1966 to 695 in 2000. This data reveals that the change of land use is influenced by various artificial factors. The NPS, which represents the declining degree of patch, decreased from 9.441 to 5.934, revealing that the change of land use has been progressing considerably. In regard to forest areas, land use reduced somewhat but did not indicate a significant change. Therefore, an analysis of the total index reveals that the edge of patch has become more complicated and that the variation index of patch has increased significantly. However, this study reveals that barriers to block pollution have weakened as a result and that there is a need to concentrate on the implementation and the management of the Riparian Buffer Zone. Consequently, this study reveals that substantial research is necessary in order to carry out the proper management of the Riparian Buffer Zone, especially in light of the distribution type of each patch and the change in conditions regarding them.

• Korean Journal of Environmental Agriculture
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• v.21 no.4
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• pp.243-247
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• 2002

Irrigation water quality along Donjin river watershed was monitored to find a possible pollutant, for maintaining water quality to achieve food safety through water quality preservation of river. As a pollution indicators, such as Biological Oxygen Demand(BOD), Chemical Oxygen Demand(COD), Total Nitrogen(T-N), and Total Phosphate(T-P) in Dongjin river were examined from May to November in 2001. The results were as follows : The BOD level of Dongjin river ranged from 2.84 to 6.45 mg/L, which would be in a II$\sim$IV grade of the potable water criteria by Ministry of Environment. Averaged BOD level of downstream DJ6(After Jeongupcheon confluence) was 4.07 mg/L. The average COD level of Dongjin river ranged from 11.20 to 32.96 mg/L. COD level of DJ6 rapidly increased rapidly after the junction of Dongjin river and Jungupcheon because it showed the latter had relatively high pollution level. T-N content were significantly high in all sites of Dongjin river ranged through 4.16 to 5.84 mg/L. T-P examined high concentration than another thing point by 0.19 mg/L after Jeongupcheon confluence as BOD and COD. COD of main stream was expressed high concentration to dry season after rainy season. In case of T-P, pollution degree of dry season before rainy season appeared and examined that quality of water was worsened go by dry season after rainy season. The water quality of Dongjin river was deteriorated with inflow of Jungupcheon polluted by municipal and industrial sites near Jungup city.

• Journal of Environmental Policy
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• v.10 no.1
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• pp.49-70
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• 2011

The numerous efforts have been made in understanding generation and transportation mechanism of nonpoint source pollutants from agricultural areas. Also, the water quality degradation has been exacerbated over the years in many parts of Korea as well as other countries. Nonpoint source pollutants are transported into waterbodies with direct runoff and baseflow. It has been generally thought that groundwater quality is not that severe compared with surface water quality. However its impacts on groundwater in the vicinity of stream quality is not negligible in agricultural areas. The SWAT model has been widely used in hydrology and water quality studies worldwide because of its flexibilities and accuracies. The spatial property of each HRU, which is the basic computational element, is not presented. Thus, the SWAT HRU mapping module was developed in this study and was applied to the study watershed to evaluate recharge rate and $NO_3-N$ loads in groundwater. The $NO_3-N$ loads in groundwater on agricultural fields were higher than on forests because of commercial fertilizers and manure applied in agricultural fields. The $NO_3-N$ loads were different among various crops because of differences in crop nutrient uptake, amount of fertilizer applied, soil properties in the field. As shown in this study, the SWAT HRU mapping module can be efficiently used to evaluate the pollutant contribution via baseflow in agricultural watershed.

• Korean Journal of Environmental Agriculture
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• v.25 no.2
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• pp.147-156
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• 2006

This study was conducted to investigate natural distribution of aquatic plane and to find out natural aquatic plants which highly absorb nutrient N and P. We surveyed vegetation within ${\pm}2m$ from streamside in 12 tributaries of the West Nakdong river watershed during May to October in 2003. Hydrophytes surveyed in tributaries of the West Nakdong river watershed were 27 families, 61 genera, 76 species, 3 varieties. Major dominance species of aquatic plants were Z. latifolia, P. communis, P. thunbergii, P. arundinacea, P. japonica, and P. distichum var. indutum. Aquatic plants having high production ability of biomass were Z. latifolia, P. communis, P. arundinacea, P. japonica, and E. crus-galli var. echinata. In the vertical distribution of hydrophytes within streams, dominant species were P. thunbergii and P. japonica in the upper stream, but dominant species in the downstream were P. communis and Z. latifolia. Species diversity or aquatic, plants was reduced, but their biomass and nutrient (T-N and T-P) content per the natural area unit $(m^2)$ were increased in the downsteaam. Nutrient N and P content of aquatic plants per the natural area unit were high at Joman river, Pyeonggangcheon, Bulam drainage canal, and Hogyecheon. Fifty-seven species of aquatic plants having high biomass were grounped into 4 categories $(I{\sim}IV)$ according to their nutrient content per dry weight unit. I group $(T-N,\;\geqq20gkg^{-1}\;&\;P_2O_5,\;\geqq7gkg^{-1})$ was comprised of 3 submerged plants (H. verticillata, P. crispus, and C. demersum), e emergent plants (O. javanica, P. distichum var. indutum, and R. sceleratus), 1 suspended plant (T. japonica), and 1 riparian plant (A. lobatum). Otherwise, in classification of natural hydrophytes according to their nutrient content per natural area unit, Z. latifolia, P. communis, P. longiseta, P. arundinacea, and P. distichum var. indutum possessing great biomass productivity as emergent plants were included in I group $(T-N,\;\geqq1gm^{-2}\;&\;P_2O_5,\;\geqq0.7gm^{-2})$.

• Journal of Korea Water Resources Association
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• v.51 no.10
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• pp.863-874
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• 2018

The purpose of this study is to evaluate the future climate change impact on stream aquatic ecology health of Han River watershed ($34,148km^2$) using SWAT (Soil and Water Assessment Tool) and random forest. The 8 years (2008~2015) spring (April to June) Aquatic ecology Health Indices (AHI) such as Trophic Diatom Index (TDI), Benthic Macroinvertebrate Index (BMI) and Fish Assessment Index (FAI) scored (0~100) and graded (A~E) by NIER (National Institute of Environmental Research) were used. The 8 years NIER indices with the water quality (T-N, $NH_4$, $NO_3$, T-P, $PO_4$) showed that the deviation of AHI score is large when the concentration of water quality is low, and AHI score had negative correlation when the concentration is high. By using random forest, one of the Machine Learning techniques for classification analysis, the classification results for the 3 indices grade showed that all of precision, recall, and f1-score were above 0.81. The future SWAT hydrology and water quality results under HadGEM3-RA RCP 4.5 and 8.5 scenarios of Korea Meteorological Administration (KMA) showed that the future nitrogen-related water quality in watershed average increased up to 43.2% by the baseflow increase effect and the phosphorus-related water quality decreased up to 18.9% by the surface runoff decrease effect. The future FAI and BMI showed a little better Index grade while the future TDI showed a little worse index grade. We can infer that the future TDI is more sensitive to nitrogen-related water quality and the future FAI and BMI are responded to phosphorus-related water quality.

• Journal of Environmental Impact Assessment
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• v.27 no.6
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• pp.685-694
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• 2018

We measured ecological niche space (ENS) using carbon and nitrogen stable isotope ratios of benthic macroinvertebrates to estimate its applicability for large river assessment. In particular, we compared ENSs of selected macroinvertebrates between upper and lower area of Seungchon Weir in Yeongsan River to estimate the impact of weir on biological community. We also measured basic water quality and community indices including benthic macroinvertebrates index (BMI) to estimate their correlations with calculated ENS. ENS was calculated using the Bayesian Stable Isotope in R statistics (package "SIBER"). The results showed that seasonal variations in water quality and community indices were found, but there was no apparent tendency between upper and lower area of the Seungchon Weir in June (before rainy season) and August (after rainy season). However, ENS of benthic macroinvertebrates markedly decreased across the weir in both June and August regardless of changes in water quality. This means the physical change of the stream due to the weir cause decrease of ecological isotopic niche space of benthic macroinvertebrates regardless of water quality, suggesting physical modification by the weir can affect the interaction between habitat condition and macroinvertebrates. Therefore, the ecological isotopic niche space can be a useful supplementary indicator for the river ecosystem assessment.

• Korean Journal of Environmental Agriculture
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• v.27 no.2
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• pp.105-110
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• 2008

The main purpose of this work is the development of water quality level model using the data such as DO, EC, BOD, $COD_{Cr},\;NH_3-N,\;NO_3-N,\;PO_4-P$, T-N, T-P, and SS in 88 agricultural streams of the Han river watersheds. To grant water quality level for each parameters, it divided into 20% respectively in the order of water quality level. On the basis of the lowest water quality level, water quality of streams was assigned. As the result, number of stream corresponding to Level Ⅰ was 0, Level II was 1 stream, Level III was 3 streams, Level IV was 22 streams, and Level V was 62 streams. By standardized canonical discriminant function coefficient, $NO_3-N$ was the highest in 0.427 at the discriminant power. According to discriminant function for water quality level, it was equal to $-4.648+3.246{\times}[NO_3-N],\;-5.084+3.456{\times}[NO_3-N],\;-4.298+3.067{\times}[NO_3-N],\;and\;-7.369+4.396{\times}[NO_3-N]$ from Level II to Level V, respectively. As a result of test at real data of the Han river watersheds in 2007, the suitability of water quality level model was high to 88.4%.

• Korean Journal of Ecology and Environment
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• v.36 no.4 s.105
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• pp.455-462
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• 2003

This study evaluated the change of water quality and chlorophyll - a at the birth stage of a large reclaimed estuarine lake (Lake Hwaong) of which the dike was finally constructed in March, 2002. Physico -chemical parameters and chlorophyll - a were investigated along a longitudinal transect, including 3 in-lake sites and 1 out-lake site from June to November, 2002. Salinity at all in-lake sites was over 21 psu during the study period, indicating that lake is still in the seawater phase. Salinity was periodically diluted at times when precipitation was high, especially in August. Chemocline was established in July near the dam site, and correspondingly vertical profile of dissolved oxygen was very clear during that Period. Total nitrogen and phosphorus concentrations at all lake sites were in the eutrophic range, and they were especially high at the stream inlet site. Nutrients concentration was not much varied vertically but significantly varied temporally, and correlated significantly with precipitation and chlorophyll-a concentration, indicating that inflowing water from the watershed seemed not to improve lake water by dilution but cause eutrophication of the lake, and thereby stimulate phytoplankton development. Based on the analyses of nutrient ratio (N/P) and trophic state deviation, both phosphorus and nitrogen appeared to limit phytoplankton growth in the lake. Phosphorus limitation appeared to be probable at all in-lake sites with being most severe at the stream inlet site. Nitrogen limitation seemed to occur at both in-lake and out-lake sites. These results indicate that in Lake Hwaong experiencing the very early stage of a reclaiming lake, water quality and phytoplankton development appear to be affect-ed largely by salinity and hydrology and nutrients from the inflowing water. Lake biogeochemistry is still very unstable, and thus further long-term study is necessary to understand the effects of seawater to freshwater conversion on lake biology and water chemistry.