• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.4
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• pp.51-59
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• 2015

Various Best Management Practices (BMPs) have been suggested to reduce soil erosion and non point source (NPS) pollutant loads from agricultural fields. However, very little research regarding water quality improvement with No-till (NT) has been performed in Korea. Thus, effects of NT were investigated in this study. The objective of the study was to investigate the effect of NT on the surface runoff and sediment discharge in a field. Eight experimental plots of $5{\times}30m$ in size and 3 % or 8 % in slope prepared on gravelly sandy loam soil were treated with Conventional-till (CT) and NT. Runoff and NPS pollution discharge were monitored and compared the treatments. The amounts of rainfall from 13 monitored events ranged from 28.7 mm to 503.5 mm. The runoff amount was reduced by 17.6~59.2 % in 3 % NT and 29.6~53.2 % in 8 % NT. The average NPS pollution loads of the 3 % NT plots and 8 % NT plot were reduced about 45.1~89.2 % and 47.7~98.0 % compared to those of the CT plots, respectively. This research revealed that NT can reduce the NPS pollution loads substantially as well as increase the crop yield. Runoff and NPS pollution loads reduction by NT method could be contribute to improve the water quality of streams in agricultural regions.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.2
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• pp.47-57
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• 2013

This study is to assess the reduction of non-point source pollution loads for rice straw mulching of upland crop cultivation at a watershed scale. For Byulmi-cheon watershed (1.21 $km^2$) located in the upstream of Gyeongan-cheon, the HSPF (Hydrological Simulation Program-Fortran) and SWAT (Soil and Water Assesment Tool), physically based distributed hydrological models were applied. Before evaluation, the model was calibrated and validated using 9 rainfall events. The Nash-Sutcliffe model efficiency (NSE) for streamflow using the HSPF was 0.62~0.76 and the determination coefficient ($R^2$) for water quality (sediment, total nitrogen T-N, and total phosphorus T-P) were 0.72, 0.62, and 0.63 respectively. The NSE for streamflow using the SWAT were 0.43~0.81 and the $R^2$ for water quality (sediment, T-N, and T-P) were 0.54, 0.87, and 0.64 respectively. From the field experiment of 16 rainfall events, the rice straw cover condition reduced surface runoff average 10.0 % compared to normal surface condition. By handling infiltration capacity (INFILT) in HSPF model, the value of 16.0 mm/hr was found to reduce about 10.0 % reduction of surface runoff. For this condition, the reduction effect of sediment, T-N, and T-P loads were 87.2, 28.5, and 85.1 % respectively. By handling soil hydraulic conductivity (SOL_K) in SWAT model, the value of 111.2 mm/hr was found to reduce about 10.0 point reduction of surface runoff. For this condition, the reduction effect of sediment, T-N, and T-P loads were 80.0, 83.2, and 78.7 % respectively. The rice straw surface covering was effective for removing surface runoff dependent loads such as sediment and T-P.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1295-1299
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• 2008

Soil erosion is a natural process and has been occurring in most areas in the watershed. However, accelerated soil erosion rates have been causing numerous environmental impacts in recent years. To reduce soil erosion and sediment inflow into the water bodies, site-specific soil erosion best management practices (BMPs) need to be established and implemented. The most commonly used soil erosion model is the Universal Soil Loss Equation (USLE), which have been used in many countries over 30 years. The Sediment Assessment Tool for Effective Erosion Control (SATEEC) ArcView GIS system has been developed and enhanced to estimate the soil erosion and sediment yield from the watershed using the USLE input data. In the last decade, the Soil and Water Assessment Tool (SWAT) model also has been widely used to estimate soil erosion and sediment yield at a watershed scale. The SATEEC system estimates the LS factor using the equation suggested by Moore and Burch, while the SWAT model estimates the LS factor based on the relationship between sub watershed average slope and slope length. Thus the SATEEC and SWAT estimated soil erosion values were compared in this study. The differences in LS factor estimation methods in the SATEEC and SWAT caused significant difference in estimated soil erosion. In this study, the difference was -51.9%(default threshold)$\sim$-54.5%(min. threshold) between SATEEC and non-patched SWAT, and -7.8%(default threshold)$\sim$+3.8%(min. threshold) between SATEEC and patched SWAT estimated soil erosion.

• Journal of Wetlands Research
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• v.22 no.3
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• pp.217-224
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• 2020

Waterlogging and unintended lake formation become the main problem in some parts of the world. Starting from 1989, the waterlogging problem was observed in the farmland of the Jarso community of Konso Woreda adjacent to the Segen River in Ethiopia. Therefore, the objectives are determining the extent and causes of unintended lake formation using GIS/RS in addition to a preliminary field survey to mitigate the problem. The analysis of satellite images revealed that over the years invasion of the irrigable land by unwanted water had increased, as, in 1989, the size of the wetland area was about 8 Km²; in 2000 the size of the un-intended lake was only 8.23 ㎢. Alarmingly the size of the lake increased to 19.68 Km² in 2014. Silting up of Weir and changing the flow of River Segen and Human Intervention and changing the natural flow of River Yanda were the main causes of this unwanted prolonged water-logging. The ecological and social environment has been degrading as the people of the waterlogged area have been experiencing some settlement and losing their land. Another problem encountered was flooding from River Barka and invasion of the farmland. Sediment control best management practices (BMPs) i.e, Removal of sediment, providing sandbags and well-scheduled maintenance; Changing the junction point of Yanda and Segen River were suggested for the long-term and short term possible remedial measures. Gabion retaining wall on the bank of the Segen River to the face of Barka River was suggested to protect the farmland from flooding.

• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.1
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• pp.3-12
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• 2008

Soil erosion is a natural process and has been occurring in most areas in the watershed. However, accelerated soil erosion rates have been causing numerous environmental impacts in recent years. To reduce soil erosion and sediment inflow into the water bodies, site-specific soil erosion best management practices(BMPs) need to be established and implemented. The most commonly used soil erosion model is the Universal Soil Loss Equation(USLE), which have been used in many countries over 30 years. The Sediment Assessment Tool for Effective Erosion Control(SATEEC) ArcView GIS system has been developed and enhanced to estimate the soil erosion and sediment yield trom the watershed using the USLE input data. In the last decade, the Soil and Water Assessment Tool(SWAT) model also has been widely used to estimate soil erosion and sediment yield at a watershed scale. The SATEEC system estimates the LS factor using the equation suggested by Moore and Burch, while the SWAT model estimates the LS factor based on the relationship between sub watershed average slope and slope length. Thus the SATEEC and SWAT estimated soil erosion values were compared in this study. The differences in LS factor estimation methods in the SATEEC and SWAT caused significant difference in estimated soil erosion. In this study, the difference was -51.9%(default threshold)${\sim}-54.5%$(min. threshold) between SATEEC and non-patched SWAT, and -7.8%(default threshold)${\sim}+3.8%$(min. threshold) between SATEEC and patched SWAT estimated soil erosion.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.5
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• pp.129-137
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• 2015

The objective of this study was to test the non-point source pollution (NPS) control by the vegetated ridge and silt fence through field monitoring. The experiment plots were established with three sizes which are 5 m width by 22 m length with 8 %, 3 % slope and 15m width by 15 m length with 6 % slope. Flumes with the floating type stage gages were installed at the outlet of each plot to monitor the runoff. For a rainfall monitoring, tipping bucket rain gage was installed within the experiment site. Water quality samples were monitored during the heavy rainfall occurred. The amount of rainfall from 4 monitored events ranged from 27.6 mm to 130 mm. The runoff reduction rate could vary depending on slope, soil, crop growth condition, rainfall amount, rainfall intensity, antecedent moisture condition, and many other factors. The runoff from vegetated ridge and silt fence treatment plots was 24.05 % and -8.28 % lower than that from control plot, respectively. The monitoring results showed that the average pollution loads reduced by vegetated ridge compared to control were BOD 36.62~53.60 %, SS 40.41~73.71 %, COD 39.34~56.41 %, DOC 49.08~53.67 %, TN 26.74~67.23 %, and TP 52.72~91.80 %; by silt fence compared to control were SS 41.73 %, COD 1.93 %, and TN 2.38 %. The paired t-test result indicated that the vegetated ridge and silt fence were statistically significant effect in SS load reduction, with a 5 % significant level. Monitored results indicated that vegetated ridge and silt fence were both effective to reduce the pollutant from the field surface runoff.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.3
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• pp.41-50
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• 2017

The purpose of this study were to evaluate the effect of best management practices (BMPs) of Haean highland agricultural catchment ($62.8km^2$) under future climate change using SWAT (Soil and Water Assessment Tool). Before future evaluation, the SWAT was setup using 3 years (2009~2011) of observed daily streamflow, suspended solid (SS), total nitrogen (T-N), and total phosphorus (T-P) data at three locations of the catchment. The SWAT was calibrated with average 0.74 Nash and Sutcliffe model efficiency for streamflow, and 0.78, 0.63, and 0.79 determination coefficient ($R^2$) for SS, T-N, and T-P respectively. Under the HadGEM-RA RCP (Representative Concentration Pathway) 4.5 and 8.5 scenarios, the future precipitation and maximum temperature showed maximum increases of 8.3 % and $4.2^{\circ}C$ respectively based on the baseline (1981~2005). The future 2040s and 2080s hydrological components of evapotranspiration, soil moisture, and streamflow showed changes of +3.2~+17.2 %, -0.1~-0.7 %, and -9.1~+8.1 % respectively. The future stream water quality of suspended solid (SS), total nitrogen (T-N), and total phosphorus (T-P) showed changes of -5.8~+29.0 %, -4.5~+2.3 %, and +3.7~+17.4 % respectively. The future SS showed wide range according to streamflow from minus to plus range. We can infer that this was from the increase of long-term rainfall variability in 2040s less rainfalls and 2080s much rainfalls. However, the results showed that the T-P was the future target to manage stream water quality even in 2040s period.

• Journal of Korean Society for Geospatial Information Science
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• v.1 no.1 s.1
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• pp.171-180
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• 1993

Concern about nonpoint source pollution associated with urban storm water has led to the development of new tools for better water quality planning. This paper presents an application of a geographic information system (GIS) for urban water quality study. The GIS was used to manage land use data for nonpoint source pollution modeling and to aggregate pollutant loadings within various types of geographic units. An empirical water quality model was used to estimate pollutant loadings based primarily on land use. A land use coverage was created by updating an old coverage through interpretation of recent photography. This land use coverage was also used to record all pollutant loadings for each land use polygon. Storm sewer maps were digitized and interpreted to create a coverage of storm sewer basins and sub-basins. By overlaying pollutant loadings with the sewer sub-basin layer, aggregated pollutant loadings for major sewer outfalls were calculated. Based on the loading information, critical areas of excessive pollutant loadings were located and the effectiveness of Best Management Practices (BMPs) to control pollutant loadings were evaluated.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.2
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• pp.15-27
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• 2009

토지이용변화가 수질에 미치는 영향을 평가하기 위하여 비점오염모형이 광범위하게 사용되고 있다. 본 연구에서는 최적관리기법이 수문 수질에 미치는 영향을 평가하기위한 통합모형시스템을 개발하였다. 통합모형시스템은 DANSAT (Dynamic Agricultural Non-point Source Assessment Tool)과 사용자 인터페이스로 구성되어 있다. DANSAT은 분포형 연속 강우사상 모형으로서 농업소유역에서의 유출량, 유사량, 농약 물질의 이동기작 등을 모의한다. DANSAT은 크게 동적변수 부모형, 수문 부모형, 유사 이용 부모형, 농약 물질 이동 부모형등 4개의 부모형으로 구성되어있다. 동적변수 부모형은 토양의 특성, 작물의 생장 및 작물 잔여물질의 분해 등을 모의하는 하부모형으로 구성되어있으며, 토지 이용 변화에 관계되는 내부 변수들의 시간적 변화를 모의한다. 수문 부모형은 차단, 증발산량, 침투량, 침루량 등을 모의하는 격자 단위 프로세스와 지표유출, 중간유출, 기저유출 및 하천에서의 물의 이동을 모의하는 유역 단위 프로세스로 구성되어있다. 유사 이동 부모형은 세류간 (interrill) 토양입자의 분리, 세류 (rill) 및 하천내의 토양분리, 운송가능량 등을 모의하며, 농약 물질 이동 부모형은 농약의 분해, 평형, 식물에 의한 흡수, 침출 등을 고려하여 농약 물질의 이동을 모의한다. 입력변수는 최적관리기법의 시 공간적인 변화를 고려할 수 있도록 계층구조로 구성하였다. 유역출구에서의 결과 출력 뿐만 아니라, 유역전체에 걸쳐 지표면과 지하수면 사이에서 물 및 오염물질의 이동량 분석을 위한 출력 및 격자단위의 상세 결과 출력을 통하여 최적관리기법을 평가하고 분석할 수 있다. 한편, 사용자 인터페이스는 모형의 구동을 위해 요구되는 광범위한 시 공간 입력 자료를 기존에 존재하는 데이터베이스를 이용하여 생성할 수 있도록 개발되었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.338-338
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• 2015

하천으로 유입되어 수질 오염을 야기하는 오염원은 오염 배출원이 명확하여 하나의 점으로 나타낼 수 있는 점오염원(Point Source)과 오염원이 명확치 않은 비점오염원(Non-point)으로 구분된다. 생활하수, 축산폐수와 같이 오염원이 명확한 점오염원은 하천 유입 이전에 처리장을 거쳐 정화작업이 가능한 반면, 비점오염원은 오염원이 명확치 않아 처리에 어려움이 따른다. 또, 오염물의 양과 이동 경로가 예측이 불가능하고 강우시에는 특별한 처리 없이 하천으로 바로 유입된다. 비점 오염원의 종류는 토사, 영양물질, 유기물질, 농약, 바이러스 등 다양하다. 이 중에서 토양에 흡착되어 이동하는 질소와 인은 하천으로 유입되어 부영양화를 야기하는 특성이 있어 더욱 처리가 필수적이다. 이러한 비점오염원으로 인한 수질 오염을 줄이기 위해 여러 최적관리기법(Best Management Practices, BMPs)이 제시되어 있으며 오염 물질의 하천 유입을 차단하는 것에 중점을 둔다. 가장 널리 이용되는 방법으로는 비점오염원 저감시설 중 하천변에 식물체를 설치하여 토양의 유실을 막는 식생대(Vegetative Filter Strip, VFS)가 있다. 식생 밀집 지역의 설치를 통해 표면 유출을 차단하고 토양 유실 감소와 수체로의 오염물질 확산을 막을 수 있다. 이에 VFSMOD-w를 이용하여 강우시 식생대를 통한 토양 유실 감소 효율에 대한 연구를 수행하였다. 연구 대상 지역으로 비교적 수문 및 토양 자료가 풍부한 청미천 유역을 선정하였다. 그 결과, 식생대의 길이와 식생대 내 식물체의 파종간격이 가장 지배적인 영향을 미치는 것이 확인된다. 이때, 식물체의 종류는 식물체 파종으로 인해 변화되는 토양의 수정된 Manning의 조도계수로 구분한다. 모든 강우 및 식물체 조건이 동일할 때, 식생대 내 식물의 파종 간격이 좁고 식생대의 길이가 길수록 토사 저감 효율이 증가하는 결과가 도출되었다. 식물체의 높이, 식물체의 종류 및 식물의 파종간격이 입력 자료로 요구되나 이 중 식물체의 높이는 토사 저감 효율에 영향을 미치지 않는 것으로 나타났다. 또, 동일한 강우 조건에서 식생대의 길이가 0.5 m에서 1.0 m로 2배 증가하였을 때 토사 저감 효율이 두 경우 모두 95% 이상의 효율을 보이는 것이 나타났다. 이는 식생대의 길이가 증가할수록 토사 저감 효율이 증가하나 일정 길이 이상이 되면 대부분의 토사가 저감되는 것을 의미한다. 결론적으로 식생의 파종 간격이 좁을수록 토사 저감 효율이 증가하더라도 식물체의 성장을 고려한 적절한 파종 간격을 선정하여야 한다. 즉, 식생대의 설치는 적절한 파종 간격 및 식생대 길이를 식생대 설치지역의 강우 특성에 따라 결정지어야 한다고 판단된다.