• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.6
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• pp.65-71
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• 2018

The Long-Term Hydrologic Impact Assessment (L-THIA) model is a quick and straightforward analysis tool to estimate direct runoff and nonpoint source pollution. L-THIA was originally implemented as a spreadsheet application. GIS-based versions of L-THIA have been developed in ArcView 3 and upgraded to ArcGIS 9. However, a major upgrade was required for L-THIA to operate in the current version of ArcGIS and to provide more options in runoff and NPS estimation. An updated L-THIA interfaced with ArcGIS 10.0 and 10.1 has been developed in the study as an ArcGIS Desktop Tool. The model provides a user-friendly interface, easy access to the model parameters, and an automated watershed delineation process. The model allows use of precipitation data from multiple gauge locations for the watershed when a watershed is large enough to have more than one precipitation gauge station. The model estimated annual direct runoff well for our study area compared to separated direct runoff in the calibration and validation periods of ten and nine years. The ArcL-THIA, with a user-friendly interface and enhanced functions, is expected to be a decision support model requiring less effort for GIS processes or to be a useful educational hydrology model.

• Journal of Korean Society on Water Environment
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• v.25 no.6
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• pp.984-993
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• 2009

There have been growing concerns of algal growth at Daecheong reservoir due to eutrophication with excess nutrient inflow. Rainfall-driven runoff and pollutant from watershed are responsible for eutrophication of the Daecheong reservoir. In this study, two subwatersheds of the Daecheong reservoir were selected and water quality characteristics were analyzed. The L-THIA ArcView GIS model was used for evaluation of direct runoff and water quality. The $R^2$ and the EI value for direct runoff were 0.95 and 0.93 at Wol-oe watershed and were 0.81, 0.71 at An-nae watershed, respectively. The $R^2$ for SS, T-P were 0.53, 0.95 at Wol-oe watershed and 0.89, 0.89 at An-nae watershed, respectively. It has been proven that the L-THIA ArcView GIS model could be used for evaluating direct runoff and pollutant load from the watershed with reasonable accuracies.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1139-1143
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• 2010

대청호 수질관리를 위한 대책 수립시 상류유역의 유출 및 오염부하배출 특성을 평가하는 것이 중요하다. 유역의 수환경 영향을 평가하기 위해서 복잡한 수문 수질 모델을 이용하는데 사용자 편의성을 고려한 모델 개발과 이용이 필요하다. L-THIA ArcView GIS 모형은 토지이용도, 토양도, 일강우 자료만으로 직접유출의 모의가 가능하여 전 세계적으로 널리 이용되고 있다. 본 연구에서는 L-THIA ArcView GIS 모형을 이용하여 대청호 상류유역인 안내천, 월외천 유역의 직접유출 및 비점오염 배출부하 특성을 평가하였다. 직접 유출량 평가 결과, 결정계수($R^2$)와 유효지수(EI)가 월외천 유역 및 안내천 유역에서 각각 0.95, 0.93 및 0.81, 0.71로 나타나, L-THIA ArcView GIS 모형이 실측치를 잘 재현하는 것으로 나타났다. 강우유출수에 포함된 SS 및 T-P 오염부하량 평가결과, 결정계수($R^2$)가 월외천 유역과 안내천 유역에서 각각 0.53, 0.95 및 0.89, 0.89로 평가되었다. 또한 유효지수(EI)가 월외천 유역과 안내천 유역에서 각각 0.44, 0.95 및 0.98, 0.99로 평가되었다. SS 부하량 평가 결과에서 월외천 유역이 안내천 유역보다 정확성이 낮은 것은 지역특성에 따라 SS 부하량 차이가 크기 때문이다. 따라서 L-THIA ArcView GIS 모형의 지속적인 개선이 이루어진다면 대청호 만입부 상류유역에서의 각종 수질관리대책 평가에 활용될 수 있을 것으로 판단된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1802-1806
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• 2006

It is important to consider the effects of land-use changes on surface runoff, stream flow, and groundwater recharge. Expansion of urban areas significantly impacts the environment in terms of ground water recharge, water pollution, and storm water drainage. Increase of impervious area due to urbanization leads to an increase in surface runoff volume, contributes to downstream flooding and a net loss in groundwater recharge. Assessment of the hydrologic impacts or urban land-use change traditionally includes models that evaluate how land use change alters peak runoff rates, and these results are then used in the design of drainage systems. Such methods however do not address the long-term hydrologic impacts of urban land use change and often do not consider how pollutants that wash off from different land uses affect water quality. L-THIA (Long-Term Hydrologic Impact Assessment) is an analysis tool that provides site-specific estimates of changes in runoff, recharge and non point source pollution resulting from past or proposed land-use changes. It gives long-term average annual runoff for a land use configuration, based on climate data for that area. In this study, the environmental and hydrological impact from the urbanized basin had been examined with GIS L-THIA in Korea.

• Journal of The Korean Society of Agricultural Engineers
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• v.52 no.1
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• pp.1-11
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• 2010

Generation and transportation of runoff and pollutant loads within watershed generated eutrophication at Daecheong reservoir. To improve water quality at Daecheong reservoir, the best management practices should be developed and applied at upper watersheds for water quality improvement at downstream areas. In this study, two small watersheds of upper Daecheong reservoir were selected. The Long-Term Hydrologic Impact Assessment (L-THIA) model has been widely used for the estimation of the direct runoff worldwide. To apply the L-THIA ArcView GIS model was evaluated for direct runoff and water quality estimation at small watershed. And the Web-based Hydrograph Analysis Tool (WHAT) was used for direct runoff separating from total flow. As a result, the $R^2$ (Coefficient of determination) value and Nash-Sutcliffe coefficient value for direct runoff comparison at An-nae watershed were 0.81 and 0.71, respectively. And the $R^2$ value and Nash-Sutcliffe coefficient value at Wol-oe were 0.95 and 0.93. The $R^2$ value of BOD, TOC, T-N and T-P at An-nae watershed were BOD 0.94, TOC 0.81, T-N 0.94 and T-P 0.89. And the $R^2$ value of BOD, TOC, T-N and T-P at Wol-oe watershed were BOD 0.80, TOC 0.93, T-N 0.86 and T-P 0.65. The result that estimated pollutant loadings using the L-THIA ArcView GIS model reflected well the measured pollutant loadings except for T-P in Wol-oe watershed. With L-THIA ArcView GIS model, the direct runoff and non-point pollutant (NPS) loadings in the watershed could be analyzed through simple input data such as daily rainfall, land uses, and hydrologic soil group.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.4
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• pp.78-88
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• 2003

The land use changes from non-urban areas to urban areas lead to the increased impervious areas, consequently increased direct runoff and higher peak runoff. Urban areas have also been recognized as significant sources of Nonpoint Source (NPS) pollution, while agricultural activities have been known as the primary sources of NPS pollution. Many features of the L-THIA/NPS GIS, L-THIA/NPS WWW system have been enhanced to provide easy-to-use system. The L-THIA model was applied to the Little Eagle Creek (LEC) watershed in Indiana to evaluate the accuracy of the model. The L-THIA/NPS GIS estimated yearly direct runoff values match the direct runoff separated from U.S. Geological Survey stream flow data reasonably. The $R^2$ and Nash-Sutcliffe values are 0.67 and 0.60, respectively. The L-THIA estimated runoff volume and total nitrogen loading for each land use classification in the LEC watershed were computed. The estimated runoff volume and total nitrogen loading in the LEC watershed increased by 180% and 270% for the 20 years. Urbanized areas -"Commercial", "High Density Residential", and "Low Density Residential"- of the LEC watershed made up around 68% of the 1991 total land areas, however contributed more than 92% of average annual runoff and 86% of total nitrogen loading. Therefore, it is essential to consider the impacts of land use change on hydrology and water quality in land use planning of urbanizing watershed.nning of urbanizing watershed.

• Journal of Korean Society of Rural Planning
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• v.8 no.2 s.16
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• pp.3-16
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• 2002

의사결장지원시스템은 다양한 분야에 적용되어 왔으며, 그 중 수자원 및 수질 관련 분야에도 다각적으로 적용되어 왔다. 본 연구에서는 미 농무성의 자연자원보전국(NRCS, Natural Resources Conservation Service)에서 개발한 유출곡선법(Curve Number Method)과 EMC(Event Mean Concentration)을 사용한 L-THIA(Long-Term Hydrologic Impact Assessment) 수문/수질 모형을 강우자료 데이터베이스, 웹기반 지리정보시스템, 웹 사용자 편의 시스템과 통합한 수문/수질 L-THIA web 의사결정지원시스템을 개발하였다. L-THIA web은 도시계획가나 지방자치단체, 또는 지방의 공동체가 사용할 수 있도록 쉽고 단순한 사용자 편의 시스템을 제공하고 있으며, 미국의 50개 본토의 주와 카운티(County) 이름으로 기상자료와 수문토양분류(Hydrologic Soil Group)을 인터넷 지리정보시스템을 이용하여 제공하고 있다. 본 연구는 지방자치단체 및 지역공동체의 실무자를 사용자로 수문/수질 평가 및 관리를 위한 시스템으로 유용하게 활용될 수 있을 것으로 사료된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1558-1562
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• 2007

우리나라 지형은 전체의 70%가 산지로 이루어져 있다. 특히 강원도 지역과 같이 산지가 대부분인 지역에서는 경사도에 따라 강우에 의한 유출특성이 크게 달라질 수 있으므로 지형의 경사가 고려된 유출량 산정방식이 필요하다. 현재 유출량 산정 방식에 많이 이용되고 있는 SCS의 CN값은 미국의 중서부 지역과 같이 경사도 5%미만인 지역에서의 유출량 산정에 적합한 유출곡선지수이다. 경사도 5%에서 유출량 산정에 적합한 CN값을 우리나라의 강원도 지형과 같이 복잡하고 경사도가 심한 지역에 적용하기에는 부적합하다. 따라서 본 연구에서는 연구대상지역인 도암댐 유역의 평균 25.8% 경사도를 고려한 직접유출량을 산정하여 기존 평균 경사도 5%일 때의 직접유출량과 비교분석하였다. 본 연구의 비교분석에 있어서 직접유출의 모의가 가능한 Long-Term Hydrologic Impact Assessment (L-THIA) ArcView GIS 모델을 사용하였고 모델의 적용성 평가를 위해 수문분석에 사용되고 있는 WHAT 모듈을 이용하여 분리된 직접유출과 비교하였다. 그 결과 유출량 산정을 위해 CN값 산정시 강원도 지형과 같이 지형이 복잡하고 경사가 심한 지형에 있어서는 유역의 경사도를 고려하여 유출을 모의해야 한다는 것을 알 수 있다.