• Journal of Environmental Science International
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• v.26 no.1
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• pp.119-131
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• 2017

This study evaluated the feasibility of recovering and recycling nitrogen (N) and phosphorus (P) from livestock excreta as struvite ($MgNH_4PO_4{\cdot}6H_2O$) in South Korea. Our experimental results showed that struvite precipitation was a very effective way to recover N and P from livestock excreta. Moreover, our study demonstrated that struvite precipitates from livestock excreta (SPL) contain higher concentrations of N, P, and magnesium (Mg) as compared to compost and liquid manure from livestock excreta. In addition, although SPL contain high concentrations of copper (Cu) and zinc (Zn), they meet the fertilizer criteria for concentrations of heavy metals. In South Korea, SPL cannot currently be used as a fertilizer due to legal constraints. Legal permission for SPL use would offer greater choice in livestock excreta management. In conclusion, recovery and recycling of N and P from livestock excreta as struvite can be an effective tool for managing nutrients in livestock excreta.

• Journal of Korean Society on Water Environment
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• v.24 no.4
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• pp.488-498
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• 2008

Soil and Water Assessment Tool (SWAT) model have been widely used in simulating hydrology and water quality analysis at watershed scale. The SWAT model extracts topographic feature using the Digital Elevation Model (DEM) for hydrology and pollutant generation and transportation within watershed. Use of various DEM cell size in the SWAT leads to different results in extracting topographic feature for each subwatershed. So, it is recommended that model users use very detailed spatial resolution DEM for accurate hydrology analysis and water quality simulation. However, use of high resolution DEM is sometimes difficult to obtain and not efficient because of computer processing capacity and model execution time. Thus, the SWAT Topographic Feature Extraction Error (STOPFEE) Fix module, which can extract topographic feature of high resolution DEM from low resolution and updates SWAT topographic feature automatically, was developed and evaluated in this study. The analysis of average slope vs. DEM cell size revealed that average slope of watershed increases with decrease in DEM cell size, finer resolution of DEM. This falsification of topographic feature with low resolution DEM affects soil erosion and sediment behaviors in the watershed. The annual average sediment for Soyanggang-dam watershed with DEM cell size of 20 m was compared with DEM cell size of 100 m. There was 83.8% difference in simulated sediment without STOPFEE module and 4.4% difference with STOPFEE module applied although the same model input data were used in SWAT run. For Imha-dam watershed, there was 43.4% differences without STOPFEE module and 0.3% difference with STOPFEE module. Thus, the STOPFEE topographic database for Soyanggang-dam watershed was applied for Chungju-dam watershed because its topographic features are similar to Soyanggang-dam watershed. Without the STOPFEE module, there was 98.7% difference in simulated sediment for Chungju-dam watershed for DEM cell size of both 20 m and 100 m. However there was 20.7% difference in simulated sediment with STOPFEE topographic database for Soyanggang-dam watershed. The application results of STOPFEE for three watersheds showed that the STOPFEE module developed in this study is an effective tool to extract topographic feature of high resolution DEM from low resolution DEM. With the STOPFEE module, low-capacity computer can be also used for accurate hydrology and sediment modeling for bigger size watershed with the SWAT. It is deemed that the STOPFEE module database needs to be extended for various watersheds in Korea for wide application and accurate SWAT runs with lower resolution DEM.

• Journal of Korean Society on Water Environment
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• v.23 no.5
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• pp.650-658
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• 2007

The Universal Soil Loss Equation (USLE) has been used in over 100 countries to estimate potential long-term soil erosion from the field. However, the USLE estimated soil erosion cannot be used to estimate the sediment delivered to the stream networks. For an effective erosion control, it is necessary to compute sediment delivery ratio (SDR) for watershed and sediment yield at watershed outlet. Thus, the Sediment Assessment Tool for Effective Erosion Control (SATEEC) was developed to compute the sediment yield at any point in watershed. In this study, the SATEEC was applied to the Sudong watershed, Chuncheon Gangwon to compare the sediment yield using area-based sediment delivery ratio (SDRA) and slope-based sediment delivery ratio (SDRS) at watershed outlet. The sediment yield using the SDRA by Vanoni, SYA and the sediment yield using the SDRS by Willams and Berndt, SYS were compared for the same sized watersheds. The 19 subwatersheds was 2.19 ha in size, the soil loss and sediment yield were estimated for each subwatershed. Average slope of main stream was about 0.86~3.17%. Soil loss and sediment yield using SDRA and SDRS were distinguished depending on topography, especially in steep and flat areas. The SDRA for all subwatersheds was 0.762, however the SDRS were estimated in the range of 0.553~0.999. The difference between SYA and SYS was -79.74~27.45%. Thus site specific slope-based SDR is more effective in sediment yield estimation than area-based SDR. However it is recommended that watershed characteristic need to be considered in estimating yield behaviors.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.6
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• pp.451-459
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• 2014

The development and reduction scheme under implementation plan of TMDLs were performed in the Jinwi watershed including 8 cities (Gunpo, Yongin, Suwon, Anseong, Osan, Uiwang, Pyeongtaek and Hwaseong) since 2012. Progress of the annual development schemes was faster than the reduction schemes in most of the cities during the planning period. Main load reduction methods included establishment and enlargement of sewage treatment plants, resources of livestock excretions, and introduction of best management practices of non-point source pollution. Especially, reduction load using recycling and composting of livestock excretions comprised 34.1% of all reduction load. It is necessary to implement methodical development and reduction scheme for making of successful performance of TMDLs and water quality improvement in the Jinwi watershed.

• Journal of Korean Society on Water Environment
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• v.28 no.6
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• pp.819-832
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• 2012

HSPF model based on BASINS was applied for the Hwaseong Reservoir watershed (HRW) to evaluate the feasibility of water quality management. The watershed was divided into 45 sub-basins considering various watershed environment. Streamflow was calibrated based on the measured meteorological data, discharge data of treatment plants and observed streamflow data for 2010 year. Then the model was calibrated against the field measurements of water qualities, including BOD, T-N and T-P. In most cases, there were reasonable agreements between observed and predicted data. The validated model was used to analyze the characterization of pollutant load from study area. As a result, Non-point source pollutant loads during the rainy season was about 66~78% of total loads. In rainy-season, water quality parameters depended on precipitation and pollutant loads patterns, but their concentration were not necessarily high during the rainy season, and showed a decreasing trend with increasing water flow. As another result of evaluation for load duration curves, in order to improve water qualities to the satisfactory level, the watershed managements considering both time-variant and pollution sources must be required in the HRW. Overall, it was found that the model could be used conveniently to assess watershed characteristics and pollutant loads in watershed scale.

• Journal of Korean Society on Water Environment
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• v.31 no.6
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• pp.715-722
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• 2015

Four major river basin in Korea has been managed with Total Maximum Daily Load(TMDL) System. Water quality indicators as targeted pollutants for TMDL were BOD and TP. In order to satisfy water quality criteria, government allocation using public treatment facilities and its action plan has been used. However, the role to improve water quality were recently faced to its limitation. It is time to require the role of non-government allocation in private discharge facilities to control good water quality. This study investigated three different scenarios in reduction demands of non-government allocations about industry and private sewages. The three different scenarios were discharge under 1) legal water quality standard, 2) water quality level in 2011 and 3) current water quality level with maximum value in group. The results showed that reduction potential in water discharge for TP indicator was 1,118kg/day, under second scenario with 20% of deduction. This results arrived at 42% of whole reduction potential costs and 0.012mg/L improvement in water quality. In conclusion, to intrigue voluntary participation in non-government allocation, various benefits such as tax reduction, tax exemption, and water quality trading should be provided.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.11a
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• pp.637-640
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• 2002

본 연구에서는 Watershed변환을 이용하여 영상을 분할할 때 과분할되는 문제점을 해결하기 위하여 영상의 경계를 강화하고 작은 지역 최소들을 효과적 제거하는 방법을 제안한다. 제안된 방법은 영상속의 양자화와 노이즈에 의한 에러를 제거하는 영상필터링 단계와 제안된 방법에 의해 CERM변환을 수행하는 영상재구성단계 그리고 Watershed변환을 수행하여 영상을 분할하는 단계로 구성되어 있다. 제안된 방법으로 영상을 분할해본 결과 과분할을 효과적으로 줄일 수 있었다.

• Journal of Korean Society on Water Environment
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• v.23 no.4
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• pp.518-526
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• 2007

There have been serious soil erosion and water pollution problems caused by highland agriculture practices at Doam-dam watershed. Especially agricultural activities, chemical and organic fertilizer and pesticide applications, soil reconditioning to maintain soil fertility are known as primary causes of soil erosion and water qaulity degradation in the receiving water bodies. Among these, soil reconditioning can accelerate soil erosion rates. To develop soil erosion prevention practices, it is necessary to estimate the soil erosion from the watershed. Thus, the Universal Soil Loss Equation (USLE) model has been developed and utilized to assess soil erosion. However, the USLE model cannot be used at watershed scale because it does not consider sediment delivery ratio (SDR) for watershed application. For this reason, the Sediment Assessment Tool for Effective Erosion Control (SA TEEC) was developed to assess the sediment yield at any point in the watershed. The USLE-based SA TEEC system can estimate the SDR using area-based SDR and slope-based SDR module. In this study, the SATEEC system was used to estimate soil erosion and sediment yield at the Doam-dam watershed using the soil properties from reconditioned agricultural fields. Based on the soil sampling and analysis, the US LE K factor was calculated and used in the SA TEEC system to analyze the possible errors of previous USLE application studies using soil properties from the digital soil map, and compared with that using soil properties obtained in this study. The estimated soil erosion at the Doam-dam watershed without using soil properties obtained in the soil sampling and analysis is 1,791,400 ton/year (123 ton/ha/year), while the soil erosion amount is 2,429,900 ton/year (166.8 ton/ha/year) with the use of soil properties from the soil sampling and analysis. There is 35 % increase in estimated soil erosion and sediment yield with the use of soil properties from soil reconditioned agricultural fields. Since significant amount of soil erosion are known to be occurring from the agricultural fields, the soil erosion and sediment yield from only agricultural fields was assessed. The soil erosion rate is 45.9 ton/ha/year without considering soil properties from soil reconditioned agricultural fields, while 105.3 ton/ha/year after considering soil properties obtained in this study, increased in 129%. This study shows that it is very important to use correct soil properties to assess soil erosion and sediment yield simulation. It is recommended that further studies are needed to develop environment friendly soil reconditioning method should be developed and implemented to decrease the speed of soil erosion rates and water quality degradation.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.2
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• pp.157-161
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• 2011

Although many researches have been carried out concerning the watershed division in natural areas, it has not been researched for the urban watershed division. If the boundary between two urban areas is indistinct because no natural distinction or no administrative division is between the areas, the boundary between the urban areas that have the different outlets (multi-outlet urban watershed) is determined by only designer of sewer system. The suggested urban watershed division model (UWDM) determines the watershed boundary to reduce simultaneously the peak outflows at the outlets of each watershed. Then, the UWDM determines the sewer network to reduce the peak outflow at outlet by determining the pipe connecting directions between the manholes that have the multi-possible pipe connecting directions. In the UWDM, because the modification of the sewer network changes the superposition effect of the runoff hydrographs in sewer pipes, the optimal sewer layout can reduce the peak outflow at outlet, as much as the superposition effects of the hydrographs are reduced. Therefore, the UWDM can optimize the watershed distinction in multi-outlet urban watershed by determining the connecting directions of the boundary-manholes using the genetic algorithm. The suggested model was applied to a multi-outlet urban watershed of 50.3ha, Seoul, Korea, and the watershed division of this model, the peak outflows at two outlets were decreased by approximately 15% for the design rainfall.

• Journal of Korean Society on Water Environment
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• v.25 no.2
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• pp.256-267
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• 2009

A method of estimating pollutant delivery ratios considering watershed physical and meteorological characteristics and flow conditions using SWAT-K watershed model was described, and pollutant delivery characteristics during dry and rainy seasons, for monthly and seasonally, and with flow regimes were investigated for the Chungju dam watershed. Delivery ratios for sediment, T-N, and T-P showed higher values over 100% during dry and winter seasons with low pollutant loads and flows, and showed relatively uniform ones under 100% during rainy and summer seasons with concentrated loads and flows. It was found that mainly wet flows during summer seasons played very important roles in investigating the delivery characteristics of total or nonpoint pollutant loads, because more than 90% of total loads were influenced by nonpoint source, and discharged with the flows. From the results, we could find out the delivery characteristics with various watershed and flow conditions which are difficult to consider by actual measurement, and could get a foothold of estimating more reasonable and scientific allocated loads for water quality standard using the reliable method of estimating delivery ratios with a watershed model.