• Journal of Environmental Impact Assessment
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• v.4 no.2
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• pp.39-57
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• 1995

The water quality model SWAT (Soil and Water Assessment Tool) was used in combination with GIS, Arc/Info and GRASS, to evaluate land use impacts in the Delaware River Basin in Pennsylvania. This paper describes application of GIS with the water quality model in the 250 square kilometer Brodhead Creek Watershed. Date used in water quality modeling include 1:250,000 digital elevation models (DEM), soil data, and monitored streamflow and curve numbers, and other input variables.

• Water Engineering Research
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• v.5 no.3
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• pp.133-146
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• 2004

Soil and water assessment tool (SWAT) was simulated based on the default parameters and a priori soil parameter estimation method in Bocheong watershed of Korea. The performance of the model was tested against the measured daily runoff data for 5 years between 1993 and 1997. The sensitivity analysis of SWAT model parameters was conducted to identify the most sensitive model parameters affecting the model output. The results of SWAT simulation indicate that the overall performance of SWAT in calculating daily runoff is reasonably acceptable. However, there is a problem in estimating the low flow components of streamflow since the low flow components simulated by SWAT are significantly different from the measured low flow. The sensitivity analysis with SWAT points out that soil related parameters are the most sensitive parameters affecting surface and ground water balance components and groundwater flow related parameters exhibit negligible sensitivity.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.349-352
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• 1998

In many circumstances, it is infeasible to simulate the daily water yield in every land use or soil type of the watershed or river basin. These situations can be simulated in“Soil and Water Assessment Tool”(SWAT) using a concept called“hydrologic response units”(HRU's) within a topographically-defined subbasin. Soil water balance, crop growth, nutrient cycling management, etc., are simulated for each HRU For the watershed of Bok-ha river, the effect of HRU's in SWAT has been studied in respect to water yield. The optimum number of HRU's was 23 based in data capacity and correlation coefficient.

• Korean Journal of Agricultural Science
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• v.48 no.3
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• pp.629-642
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• 2021

Land-use change has an important role in the hydrologic characteristics of watersheds because it alters various hydrologic components such as interception, infiltration, and evapotranspiration. For example, rapid urbanization in a watershed reduces infiltration rates and increases peak flow which lead to changes in the hydrologic responses. In this study, a physical hydrologic model the soil and water assessment tool (SWAT) was used to assess long-term continuous daily streamflow corresponding to land-use changes that occurred in the Naesungchun river watershed. For a 30-year model simulation, 3 different land-use maps of the 1990s, 2000s, and 2010s were used to identify the impacts of the land-use changes. Using SWAT-CUP (calibration and uncertainty program), an automated parameter calibration tool, 23 parameters were selected, optimized and compared with the daily streamflow data observed at the upstream, midstream and downstream locations of the watershed. The statistical indexes used for the model calibration and validation show that the model performance is improved at the downstream location of the Naesungchun river. The simulated streamflow in the mainstream considering land-use change increases up to -2 - 30 cm compared with the results simulated with the single land-use map. However, the difference was not significant in the tributaries with or without the impact of land-use change.

• Water for future
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• v.53 no.9
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• pp.17-20
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• 2020

• Korean Journal of Environmental Agriculture
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• v.33 no.1
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• pp.30-36
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• 2014

BACKGROUND: Best management practices are often implemented to control nonpoint source pollutants. Best management practices need to be simulated and analyzed for effective Best management practices implementations. Filter strip is one of effective Best management practices in agricultural areas. METHODS AND RESULTS: Soil and Water Assessment Tool model was selected to explore the effectiveness of filter strip to control total phosphorous in Golji watershed. Soil and Water Assessment Tool model was calibrated for flow and total phosphorous by Sequential Uncertainty Fittin ver.2 algorithm provided in Soil and Water Assessment Tool-Calibration and Uncertainty Procedures. Three scenarios defined by filter strip width were applied. The filter strip width of 5 m was able to reduce the most amount of total phosphorous. In other words, the total phosphorous reduction by filter strip of 5 m was 28.0%, while the reduction was 17.5% by filter strip of 1 m. However, the reduction per unit filter strip width were 17.4%, 8.0%, and 4.5% for 1 m, 3 m, and 5 m of filter strips, respectively. CONCLUSION: Best management practices need to be simulated and analyzed so that the BMP scenario can be cost-effective. A large size of BMP might be able to control large amount of pollutants, however it would not be indicated as a cost-effective strategy.

• 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 Korean Society on Water Environment
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• v.24 no.5
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• pp.569-580
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• 2008

In this study, area-weighted slope and slope length module, considering measured field slope and slope length of the agricultural fields within the subwatershed, was developed using the ArcView Avenue programming to reflect the field topography of the Soil and Water Assessment Tool (SWAT) HRU in simulating the hydrology and water quality. Flow and sediment yield estimated values of the SWAT were compared with and without applying area-weighted slope and slope length module, developed in this study. There was 103% increases in estimated sediment with area-weighted slope and slope length module for the study watershed. The soil erosion and sediment yield from only agricultural field in Hae-an watershed was also assessed. There are 111% increase in estimated soil erosion and 112% increase in estimated sediment by applying area-weighted slope and slope length module. This study shows that the area-weighted slope and slope length module needs to be utilized in estimating the HRU field slope and slope length for accurate estimation of soil erosion and nonponit source pollutant modeling with the SWAT although it is not feasible to measure topographic information for every agricultural fields within the watershed. The area-weighted slope and slope length module can be used in identifying soil erosion hot spot areas for developing cost effective and efficient soil erosion management practices.

• Journal of Korean Society on Water Environment
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• v.24 no.4
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• pp.465-472
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• 2008

Soil and Water Assessment Tool (SWAT) model was selected as a tool for assessing the effect of pollutant sources on the total loads from the Chungju Dam upstream watershed. The model was constructed through calibration of parameters related to nitrogen (N) and phosphorus (P), which was based on the runoff and sediment modeling performed in the previous research. Using this, the spatial and temporal pollutant loadings by source type were investigated. Results of this study indicated that in most forested upstream sub-watersheds, pollutant loadings from point sources were very low, and total loadings by point and non-point sources were also insignificant. On the other hand, in #14 sub-watershed including Jecheon city, the loadings by point source were relatively considerable. For the whole watershed, non-point sources accounted for 99% of sediment, 97% of N, and 93% of P loads. And monthly non-point source loadings were concentrated on rainy summer season, while point source loadings of N and P kept nearly constant throughout the year and were high on dry winter season relative to non-point source.

• 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.