• Korean Journal of Soil Science and Fertilizer
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• v.45 no.6
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• pp.890-896
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• 2012

This study was conducted to evaluate soil erosion risk with a standard unit watershed in the upper Upper Nakdong River Basin according to soil characteristics and landuse using the spatial soil erosion map. The study area is $3,605.6km^2$, which consists of 2 subbasins, 35 standard unit watersheds (Andong basin 18, Imha basin 17). As a evaluation of soil erosion potential using the spatial soil erosion map, total annual soil loss and soil loss per area estimated $2,013{\times}10^3Mg\;yr^{-1}$ (Andong basin 979, Imha basin 1,034) and $6.1Mg\;ha^{-1}yr^{-1}$ (Andong basin 6.0, Imha basin 5.2), respectively. 54.2% of soil loss was originated from Arable land (Andong basin 49.0%, Imha basin 59.0%), and the area of regions, graded as higher "Moderate" for annual soil loss, was $201.7km^2$ (Andong basin 84.9, Imha basin 116.8). Average soil loss per area of unit watersheds by classification according to soil dominant parent material types ranked "Sedimentary rock group" > "Mixed group" > "Metamorphic rock group" > "Igneous rock group". In conclusion, the results of this study inform that the classification of soil parent material type would be effective for soil erosion analysis and interpretation in the Upper Nakdong River Basin.

• Journal of the Korean Institute of Landscape Architecture
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• v.48 no.1
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• pp.25-34
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• 2020

Land use in watersheds has been shown to be a major driving factor in determining the status of the water quality of streams. In this light, scientists have been investigating the roles of riparian vegetation on the relationships between land use in watersheds and the associated stream water quality. Numerous studies reported that riparian vegetation could alleviate the adverse effects caused by land use in watersheds and on stream water quality through various hydrological, biochemical and ecological mechanisms. However, this concept has been criticized as the true effects of riparian vegetation must be assessed by comprehensive models that mimic real environmental settings. This study aimed to estimate a comprehensive structural equation model integrating topography, land use, and characteristics of riparian vegetation. We used water quality data from the Nakdong River system monitored under the National Aquatic Ecosystem Monitoring Program (NAEMP) of the Korean Ministry of Environment (MOE). Also, riparian vegetation data and land use data were extracted from the Land Use/Land Cover map (LULC) produced by the MOE. The number of structural equation models (SEMs) were estimated in Amos of IBM SPSS. Study results revealed that land use was determined by elevation, and developed areas within a watershed significantly increased the concentration of Total Nitrogen (TN) in streams and LDI in riparian vegetation. On the contrary, developed areas significantly reduced LPI and PLAND. At the same time, PLAND and LDI significantly reduced the concentration of TN in streams. Thus, it was clear that developed areas in watersheds had both a direct and an indirect impact on the concentration of TN in streams, and spatial pattern and the amount of vegetation of riparian vegetation could significantly alleviate the negative impacts of developed areas on TN concentration in streams. To enhance stream water quality, reducing developed areas in a watershed is critical for long-term watershed management plans, restoration patterns for riparian vegetation could be immediately implemented since riparian areas were less developed than most other watersheds.

• Journal of Environmental Science International
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• v.7 no.4
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• pp.441-450
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• 1998

The purpose of this study is to evaluate and to predict of eutrophication in lakes by using VollenweiderGECD model and total phosphorus concentration and inflow rate which were measurded in 1993-1996. The results of study was as follows. The annual total phosphorus loading from the watershed was calculated to be 181-195tP /yr at lake Soyang, 591-680tP/yr at lake Chungju, 420-466tP/yr at lake Taechong, 229-278tP/yr at lake Andong, 103-106tP/yr at lake Hapchon, 57-59tP/yr at lake Imha, 194-244tP/yr at lake Namgang, 8386tP /yr at lake Chuam, 99-109tP /yr at lake Somjin. These are discharged, for the most parts, from population and ftshfarm facility. TP loading on the surface area at lake Soyang was 3.0lgP/$m^2$/yr, 2.82gP/$m^2$/yr, 2.84gP/$m^2$/yr, 3. 03gP/$m^2$/yr, at lake Chungju 7.91gP/$m^2$/yr, 6.87gP/$m^2$/yr, 7.38gP/$m^2$/yr, 7.l8gP/$m^2$/yr, at lake Taechong 6.7lgP/$m^2$/yr, 7.25gP/$m^2$/yr, 7.24gP/$m^2$/yr, 6.53gP/$m^2$/yr and TP loading on the surface area of Nakdong river basin, that is, lake Andong, Imha, Hapchon and Namgang were 5.39gP/$m^2$/yr, 4.47gP/$m^2$/yr, 4. 56gP/$m^2$/yr, 4.45gP/$m^2$/yr and 2.20gP/$m^2$/yr, 2.23gP/$m^2$/yr, 2.24gP/$m^2$/yr, 2.l7gP/$m^2$/yr and 4.50gP/$m^2$/ yr, 4.50gP/$m^2$/yr, 4.54gP/$m^2$/yr, 4.43gP/$m^2$/yr and 8.25gP/$m^2$/yr, 8.48gP/$m^2$/yr, 8.48gP/$m^2$/yr, 10. 39gP/$m^2$/yr respectively. Also those of lake Chuam was 2.51gP/$m^2$/yr, 2.61gP/$m^2$/yr, 2.52gP/$m^2$/yr, 2. 54gP/$m^2$/yr and TP loading on the surface area at lake Somjin was analysed 4.09gP/$m^2$/yr, 4.l0gP/$m^2$/yr, 3.98gP/$m^2$/yr,3.73gP/$m^2$/yr. The tropic states of nine lakes can be assessed as eutrophy because phosphorus loading exceeds the critical phosphorus loading by Vollenwelder-GECD model.

• Journal of Korean Society of Water and Wastewater
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• v.34 no.5
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• pp.323-334
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• 2020

Adsorption by granule activated carbon(GAC) is recognized as an efficient method for the removal of perfluorinated compounds(PFCs) in water, while the poor regeneration and exchange cycles of granule active carbon make it difficult to sustain adsorption capacity for PFCs. In this study, the behavior of PFCs in the effluent of wastewater treatment plant (S), the raw water and the effluents of drinking water treatment plants (M1 and M2) located in Nakdong river waegwan watershed was monitored. Optimal regeneration and exchange cycles was also investigated in drinking water treatment plants and lab-scale adsorption tower for stable PFCs removal. The mean effluent concentration of PFCs was 0.044 0.04 PFHxS g/L, 0.000 0.00 PFOS g/L, 0.037 0.011 PFOA g/L, for S wastewater treatment plant, 0.023 0.073 PFHxS g/L, 0.000 0.00 PFOS g/L, 0.013 0.008 PFOA g/L for M1 drinking water treatment plant and 0.023 0.073 PFHxS g/L, 0.000 0.01 PFOS g/L, 0.011 0.009 PFOA g/L for M2 drinking water treatment plant. The adsorption breakthrough behaviors of PFCs in GAC of drinking water treatment plant and lab-scale adsorption tower indicated that reactivating carbon 3 times per year suggested to achieve and maintain good removal of PFASs. Considering the results of mass balance, the adsorption amount of PFCs was improved by using GAC with high-specific surface area (2,500㎡/g), so that the regeneration cycle might be increased from 4 months to 10 months even if powdered activated carbon(PAC) could be alternatives. This study provides useful insights into the removal of PFCs in drinking water treatment plant.

• Journal of the Korean Geographical Society
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• v.49 no.3
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• pp.321-338
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• 2014

This study aims to identify spatial distribution of estuarine wetlands in Korea, and to assess temporal variation of the wetlands in the last few decades. Widely known in environmental and coastal management, watershed-based regions which composed with Han-river(western and eastern parts), Keum-river, Yeoungsan-river, Seomjin-river, Nakdong-river, and Jeju, are analyzed to evaluate temporal change of estuarine wetlands in the 1980s, 1990s, and 2000s, through the land-cover map. Results show that estuarine wetlands dramatically decreased in Han-river(western part), Keum-river, Yeoungsan-river that estuarine circulation have been interrupted with man-made structures such as dyke and drainage. But, estuarine wetlands surrounded by forests and grasslands has been relatively less damaged. Habitat diversity providing healthy estuary ecosystem is lower in interrupted estuaries than circulated estuaries, which are composed of tidal-flat, open water, salt marsh, rocky coasts and sandy shoreline. This study indicates that spatial distribution and temporal variation of estuarine wetlands are different with estuary type and region, so estuary type with seven regions can be applied to provides a framework for estuary management strategies and to establish estuary restoration plans.

• Journal of Wetlands Research
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• v.22 no.2
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• pp.106-112
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• 2020

Wetlands play an important function and role in hydrological, environmental, and ecological, aspects of the watershed. Water level in wetlands is essential for various analysis such as for the determination of wetland function and its effects on the environment. Since several wetlands are ungauged, research on wetland water level prediction are uncommon. Therefore, this study developed a water level prediction model using multiple regression analysis, principal component regression analysis, artificial neural network, and DNN to predict wetland water level. Geumjeong-Mountain Wetland located in Yangsan-city, Gyeongsangnam-do province was selected as the target area, and the water level measurement data from April 2017 to July 2018 was used as the dependent variable. On the other hand, hydrological and meteorological data were used as independent variables in the study. As a result of evaluating the predictive power, the water level prediction model using DNN was selected as the final model as it showed an RMSE value of 6.359 and an NRMSE value of 18.91%. This research study is believed to be useful especially as a basic data for the development of wetland maintenance and management techniques using the water level of the existing unmeasured points.

• Journal of Korea Water Resources Association
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• v.47 no.9
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• pp.825-838
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• 2014

The stationary Markov chain model has been widely used as a daily rainfall simulation model. A main assumption of the stationary Markov model is that statistical characteristics do not change over time and do not have any trends. In other words, the stationary Markov chain model for daily rainfall simulation essentially can not incorporate any changes in mean or variance into the model. Here we develop a Non-stationary hidden Markov chain model (NHMM) based stochastic downscaling scheme for simulating the daily rainfall sequences, using general circulation models (GCMs) as inputs. It has been acknowledged that GCMs perform well with respect to annual and seasonal variation at large spatial scale and they stand as one of the primary sources for obtaining forecasts. The proposed model is applied to daily rainfall series at three stations in Nakdong watershed. The model showed a better performance in reproducing most of the statistics associated with daily and seasonal rainfall. In particular, the proposed model provided a significant improvement in reproducing the extremes. It was confirmed that the proposed model could be used as a downscaling model for the purpose of generating plausible daily rainfall scenarios if elaborate GCM forecasts can used as a predictor. Also, the proposed NHMM model can be applied to climate change studies if GCM based climate change scenarios are used as inputs.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.782-782
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• 2012

지금까지 우리나라에서는 도시하수, 공장폐수 등의 점오염원에 국한하여 중점적으로 수질관리를 실행하여 부분적으로 효과를 얻을 수 있었으나, 하천과 호소의 수질은 크게 향상되지 않고 있다. 이는 급속한 도시화와 산업발달로 토지개발이 가속화되고 대지, 도로, 주차장 등 불투수층 면적이 늘어남에 따라 비점오염원에 의한 하천, 호소의 수질영향도가 커지고 있기 때문이다. 인구증가로 인해 물 사용량 뿐만 아니라 이에 따라 배출되는 오염원의 종류 및 오염부하량 역시 함께 증가하고 있다. 장래의 수질관리 성공여부는 비점오염원의 효율적인 관리여부가 큰 변수로 작용할 것으로 본다. 따라서 공공수역의 수질관리를 위해서는 토지이용과 지역특성을 고려한 비점오염원 부하량의 합리적인 조사, 오염 부하량 절감을 위한 관리기술의 개발, 비점오염원 관리정책의 개발 및 수질모형을 이용한 정확한 수질예측 등이 필요하다. 따라서 본 연구에서는 공간정보를 바탕으로 한 낙동강 유역에서의 비점오염원 정량화 분석을 수행하고자 한다. 우선 대상유역으로 낙본 G유역을 선정하여 이에 대한 조사를 통해 점오염원의 실측자료를 구축하고 이를 HSPF의 입력하여 모의를 수행하여 대상유역에 대한 실측치를 이용해 모형의 보정과 검증을 수행한다. 이러한 과정을 통해 도출된 결과는 대상유역의 총 오염량을 의미한다. 따라서 위의 과정에서 도출된 매개변수를 이용하고, 점오염원을 제거한 뒤 모의를 재수행하여 나온 결과가 대상유역의 비점오염원의 양이라 판단하였다. 모의 결과 대상유역인 낙본 G유역에서 약 39% 정도의 비점오염원 비율을 보였다. 그러나 수질 및 유량 관측치를 지금까지는 국립환경과학원 낙동강물환경연구소 유량측정데이타를 사용하고 있는데 이 자료는 8일 이상 간헐적으로 측정이 수행되고 있다. 따라서 검 보정 대상이 되는 실측치의 자료의 부족과 부정확한 유역이 있음이 한계점으로 작용한다. 그러므로 추후의 신경망 모형이나 기타 실측치 보간에 있어서의 신뢰도를 높이는 기법 개발이나 측정제도의 보편적인 기술의 증대도 앞으로의 모델링에 있어서 중요할 것으로 판단된다. 또한 유역수질모형의 모델링 과정에서 좀 더 신뢰도 높은 측정자료와 그 측정자료를 활용하여 PEST 보정기법을 적용한다면 더욱 정확한 예측이 이루어질 수 있을 것이며, 본 연구에서의 평가방법을 바탕으로 유역수질모델링이 이루어진다면 보다 더 정확성 높은 비점오염원 정량화와 수질 예측이 수행될 수 있을 것이며 더 나아가 오염총량제의 수행에 효과적으로 적용될 것으로 판단된다.

• Korean Journal of Ecology and Environment
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• v.35 no.4 s.100
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• pp.249-256
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• 2002

The variation of trophic state was measured in a reservoir (Lake Andong, Korea) from 1993 to 2000. Phosphorus loading from the watershed was estimated by measuring total phosphorus concentration in the main inflowing stream (the Nakdong River). Phosphorus discharge from the pen-type fish farms was estimated from the amount of fish feed and the rate of phosphorus excretion per feed weight. The transparency in summer was about 2.0 m in 1993 and 1994, but it decreased to about 1.2 m in 1997 and 1998, and recovered to about 2.3 m in 1999 and 2000. TP increased from $11-30\;mgP/m^3$ in 1993 to $18-42\;mgP/m^3$ in 1998, but recovered to $8-13\;mgP/m^3$ in 2000, whereas TN decreased slightly from 1.81-2.96 mgN/L in 1993 to 1.17-1.80 mgN/L in 2000. TN/TP ratios decreased from 82-281 in 1993 to 21-143 in 1998, but again increased to 101-209 in 2000 due to the decrease of TP. The average chlorophyll-a concentration in growing season was in the range of $4.8-16.2\;mg/m^3$ from 1993 to 1997, but it decreased to $3.7-5.2\;mg/m^3$ after 1998. Trophic State Index had shown a gradual increase until 1996, and since then it has declined. The major cause of the trophic state recovery is thought to be the removal of fish farms in April 1998.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2B
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• pp.169-177
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• 2010

Recently due to the typhoon and extreme rainfall induced by abnormal weather and climate change, the probability of severe damage to human life and property is rapidly increasing. Thus it is necessary to create adequate and reliable flood risk map in preparation for those natural disasters. The study area is Seo-gu in Daegu which is located near Geumho river, one of the tributaries of Nakdong river. Inundation depth and velocity at each time were calculated by applying FLUMEN model to the target area of interest, Seo-gu in Daegu. And the research of creating flood risk map was conducted according to the Downstream Hazard Classification Guidelines of USBR. The 2-dimensional inundation analysis for channels and protected lowland with FLUMEN model was carried out with the basic assumption that there's no levee failure against 100 year precipatation and inflow comes only through the overflowing to the protected lowland. The occurrence of overflowing was identified at the levee of Bisan-dong located in Geumho watershed. The level of risk was displayed for house/building residents, drivers and pedestrians using information about depth and velocity of each node computed from the inundation analysis. Once inundation depth map and flood risk map for each region is created with this research method, emergency action guidelines for residents can be systemized and it would be very useful in establishing specified emergency evacuation plans in case of levee failure and overflowing resulting from a flood.