Youn Shik Park

Development of new R, C and SDR modules for the SATEEC GIS system

Soil erosion is a natural phenomenon, but accelerated soil erosion is occurring with increased construction activities and intensive agricultural cultivation within many watersheds in recent years. To develop efficient soil erosion control best management practices, the soil erosion status in the target areas first needs to be understood spatially and temporally. The SATEEC system has been widely used for soil erosion studies because of its ease-of-use and limited input data requirement. However, SATEEC cannot be used for spatiotemporal analysis of soil erosion studies. Thus, the time-variant R, C, and GA-SDR modules were developed and integrated with the SATEEC system. The enhanced SATEEC 2.0 system estimated sediment yield values were compared with measured data for the Imha watershed. The R^2 value and the Nash-Sutcliffe coefficient were 0.72 and 0.72, respectively for calibration and 0.91 and 0.88, respectively for validation with the time-variant R, C and GA-SDR modules. The statistics indicate the enhanced SATEEC 2.0 system with these modules can be used for spatial and temporal analysis of soil erosion and sediment yield with higher accuracy and a limited input dataset, which is the primary philosophy of the SATEEC ArcView GIS system. Since the daily USLE C database was obtained from SWAT runs using the climate data and agricultural management data in Korea, the daily USLE C database should be adjusted depending on the climate condition and agricultural management when the SATEEC is applied to other watersheds having different climate and agricultural management systems.

Development of Web-based Load Duration Curve system for analysis of total maximum daily load and water quality characteristics in a waterbody

In many states of the US, the total maximum daily load program has been widely developed for watershed water quality restoration and management. However, the total maximum daily load is often represented as an average daily pollutant load based on average long-term flow conditions, and as such, it does not adequately describe the problems they aim to address. Without an adequate characterization of water quality problems, appropriate solutions cannot be identified and implemented. The total maximum daily load approach should consider adequate water quality characterizations based on overall flow conditions rather than on a single flow event such as average daily flow. The Load Duration Curve, which provides opportunities for enhanced pollutant source and best management practice targeting both in the total maximum daily load development and in water quality restoration efforts, has been used for the determination of appropriate total maximum daily load targets. However, at least 30 min to an hour is needed for unskilled people based on our experiences to generate the Load Duration Curve using a desktop-based spreadsheet computer program. Therefore, in this study, the Web-based Load Duration Curve system (https://engineering.purdue.edu/∼ldc/) was developed and applied to a study watershed for an analysis of the total maximum daily load and water quality characteristics in the watershed. This system provides diverse options for Flow Duration Curve and Load Duration Curve analysis of a watershed of interest in a brief time. The Web-based Load Duration Curve system is useful for characterizing the problem according to flow regimes, and for providing a visual representation that enables an easy understanding of the problem and the total maximum daily load targets. In addition, this system will be able to help researchers identify appropriate best management practices within watersheds.

Evaluation of SWAT sub-daily runoff estimation at small agricultural watershed in Korea

A study was undertaken for the prediction of runoff flow from 0.8 ha field-sized agricultural watershed in South Korea using Soil and Water Assessment Tool (SWAT) sub-daily. The SWAT model with sub-daily configuration predicted flow from the watershed within the range of acceptable accuracy. The SWAT sub-daily simulations were carried out for a total of 18 rainfall events, 9 each for calibration and validation. Overall trend and extent of matching simulated flow for the rainfall events in 2007–2008 with measured data during the calibration process were coefficient of determination (R2) value of 0.88 and Nash and Sutcliffe Efficiency (ENS) value of 0.88. For validation, R2 and ENS values were 0.9 and 0.84, respectively. Whereas R2 and ENS values for simulation results using daily rainfall data were 0.79 and −0.01, respectively, that were observed to be out of acceptable limits for the model simulation. The importance of higher time resolution (hourly) precipitation records for flow simulation were evaluated by comparing R2 and ENS with 15 min, 2 h, 6 h and 12 h precipitation data, which resulted in lower statistics with increases in time resolution of precipitation data. The SWAT sub-daily sensitivity analysis was performed with the consideration of hydraulic parameter and was found as in the rank order of CN2 (curve number), ESCO (soil evaporation compensation factor), GW_DELAY (ground water delay time), ALPHA_BF (base flow alpha factor), GWQMN (a threshold minimum depth of water in the shallow aquifer required for return flow to occur), REVAPMN (minimum depth of water in shallow aquifer for re-evaporation to occur), LAT_TIME (lateral flow travel time) respectively. These sensitive parameters were evaluated at 10% higher and lower values of the parameters, corresponding to 70.5% higher and 23.2% lower in simulated flow out from the SWAT model. From the results obtained in this study, hourly precipitation record for SWAT sub-daily with Green-Ampt infiltration method was proven to be efficient for runoff estimation at field sized watershed with higher accuracies that could be efficiently used to develop sitespecific Best Management Practices (BMPs) considering rainfall intensity, rather than simply using daily rainfall data.

Assessment of soil loss in South Korea based on land-cover type

Soil loss poses a significant threat to the long-term sustainability of hydrological systems, the environment, and agriculture. In this regard, efficient soil management relies on accurate quantification of soil loss. To this end, the Organization for Economic Cooperation and Development (OECD) standard of soil erosion, developed for agricultural areas, has been applied in many countries, including South Korea. Due to the lack of standard methods for assessing soil erosion in South Korea, the OECD standard has been applied to non-agricultural regions of Korea despite the possibility that local soil erosion characteristics may differ from those in agricultural areas. Such an approach might give erroneous information on soil loss to policy and decision makers. This study estimated soil loss for eight different land cover-types in Korea using the universal soil loss equation, and compared the results with those from the unmodified OECD soil erosion standard. Estimated soil loss differed considerably among land-cover types. The results have implications on the limitations in applying the OECD soil erosion standard to soil management in Korea. Thus, this study suggests a modified soil erosion standard for efficient soil management.

Analysis of Suspended Solids Reduction by Vegetative Filter Strip for Cultivated Area Using Web GIS-Based VFSMOD

The study was performed to simulate the reduction efficiency of suspended solids (SS) for cultivated land located at riverine area at the Namhan River and the Bukhan River watershed sites (site A, B, C) under the rainfall conditions using HUFF & SCS UH-based VFS Design module of Web GIS-based VFSMOD System. The study indicates that the field 5% sloped, located at Bukhan River watershed (site A), requires at least 0.5 m width of Vegetative Filter Strip (VFS) to reduce 70% of SS while the field 10% sloped requires the at least 1.0~1.5 m width of VFS to reduce 70% SS, under the condition 106.2 mm of rainfall event and bell pepper or corn of crops. Against the conditions 95.1 mm of rainfall event and sweet potato or soy bean of crops, the field 5% sloped, located at Namhan River watershed (site B) requires at least 0.5 m width of VFS to reduce 70% of SS while the field 10% sloped requires at least 1.0 m width of VFS to reduce 50% SS. The crops sweet potato and soy bean are cultivated in the site C, located at Namhan River watershed, 1 m of VFS is capable of 64.0% and 62.0% of SS reduction against 102.6 mm and 151.2 mm rainfall conditions respectively, for the 5% sloped field. The result supports that VFS is one of most potential methods to reduce SS from cultivated area, which is environment-friendly hydrologic structure. The VFS design, however, needs to be simulated before its installation in the field, the simulation needs to consider not only various characteristics of the field but also different conditions affecting the VFS, using a model capable to consider a lot of factors.

Estimation of Pollutant Load Using Genetic-algorithm and Regression Model

Received: 22 January 2014 / Revised: 5 February 2014 / Accepted: 7 February 2014 Copyright c 2014 The Korean Society of Environmental Agriculture This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Assessment of the Effects of Urbanization on the Watershed Streamflow

ABSTRACT 도시화는 불투수면적의 증가로 인해 수문학적 변화를 초래하며 또한 지하수량의 감소와 지표유출의 증가와 같은 현상이 발생한다. 따라서 본 연구의 목적은 일유량을 기본으로 한 토지이용 변화 현상에 대한 영향을 정량적이고 공간적으로 다른 토지이 용도를 이용하여 산정하는 것이다. 이에 따라 본 연구에서는 ARCSWAT의 SWAT2005 버전을 이용하여 갑천 유역을 일유량으로 모의 하였다 . 모형의 검보정 후, 1997년부터 2001년 일유량으로 모의된 결과를 통계학적으로 분석하였고 , 모의된 유량은 Mann-Whiteny method로 테스트 하였다. 도시 면적이 28 % 차이가 있는 경우 SWAT의 유량 모의 결과는 5 % 유의수준에서 도시화의 영향이 모의된 유량에 크게 영향을 주는 것으로 나타났다 . 그러나 도시화의 공간적 변화는 5 % 유의수준에서 유량의 변화에 미치는 영향이 거의 없는 것으로 나타났다. Keywords: ARCSWAT, Flood, Impervious area, Mann-Whitey method, Urbanization I. INTRODUCTION * As nature is affected by human activities, the hydrologic cycle cannot avoid the new circumstance. Climate change, groundwater use, and land cover change are typical factors affecting change of hydrologic response. Urban area, in particular, has such hydrologic characteristics as the decrease of infiltration rate and the reduced amount of evaporation. As impervious areas like buildings, roads, compacted soil, and underground structures block the infiltration of rainfall, more surface runoff or overland flow results. There are a variety of sources influencing hydrologic response in urban area, but it is not an easy matter to show the effect of urbanization quantitatively. The changes of population and

Analysis of Baseflow Contribution to Streamflow at Several Flow Stations

Abstract Streamflow is typically divided into two components that are direct runoff and baseflow, it is required to analyze and estimate behaviors of those two flow components to understand watershed characteristics so that watershed management plan can be effective in pollutant reductions. Since pollutant load behaviors in a stream or river are variable by flow component behaviors , best management practices need to be applied in a watershed based on the pollutant load behaviors varying with flow components. Thus, baseflow behaviors were analyzed separating baseflow from streamflow data collected from fifteen streamflow gaging stations in the 4 major river watersheds which are the Han river, Nakdong river, Guem river, and Yeongsan·Somjin river watersheds. Moreover, precipitation trends throughout the 4 River Systems were investigated, thus daily precipitation data were collected from sixty-five locations. The Hank river watershed displayed the largest precipitation (925.2 mm) in summer but the lowest precipitation (71.8 mm) in winter, indicating the watershed has the most fluctuating precipitation characteristic. While the precipitation trends in the Four River Systems varied, a distinct feature in baseflow trends was not found, moreover baseflow percentages to streamflow were typically greater than 50% in the Four River Systems. As shown in this study, it would be expected significant amount of pollutants could be contributed to the stream in the form of baseflow at the watershed.

Development of Web-based SWAT System

Non Point Source Pollution (NPSP) load had been arising as a significant environmental issue. Especially excessive NPS input to the water bodies is causing serious impacts on river or stream ecosystems worldwide. To develop efficient best management practices for water quality improvement, hot spot target areas first need to be identified and understood to develop proper action plans to restore river ecosystem. For simulation of NPSP influences on watershed, the Soil and Water Assessment Tool model (SWAT) has been widely used in many countries, by many researchers. But the SWAT model is a desktop-based system. Therefore there are many disadvantages over advantages of desktop-based system, especially when it is used for watershed management related decision making processes. In this study, the Web GIS-based SWAT system was developed, which provides Web GIS interface for the SWAT model installed on the server-side. The Web GIS-based SWAT provides simple-to-use interface to allow users to change the subbasin and HRU level input parameters, such as filter strip width, surface cover management, main channel slope, initial SCS CN II value, and so on. The Web-based SWAT system will provides valuable scientific information for watershed decision makers with ease-of-use Web GIS-based interface.

Application and Effectiveness Analysis of SWAT Filter Strip in Golji Watershed

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.