하천 BOD 환경가뭄 식별

서지유 ( Seo Jiyu ),원정은 ( Won Jeongeun ),정하은 ( Jung Haeun ),김상단 ( Kim Sangdan ) 한국물환경학회 2022 한국물환경학회·대한상하수도학회 공동 춘계학술발표회 Vol.2022 No.-

낙동강 유역 주요하천 구간에서 가뭄이 수온에 미치는 영향의 확률론적인 평가

서지유 ( Seo Jiyu ),원정은 ( Won Jeongeun ),이호선 ( Lee Hosun ),김상단 ( Kim Sangdan ) 한국물환경학회 2021 한국물환경학회지 Vol.37 No.5

In this work, we analyzed the effects of drought on the water temperature (WT) of Nakdong river basin major river sections using Standardized Precipitation Index (SPI) and WT data. The analysis was carried out on a seasonal basis. After calculating the optimal time scale of the SPI through the correlation between the SPI and WT data, we used the copula theory to model the joint probability distribution between the WT and SPI on the optimal time scale. During spring and fall, the possibility of environmental drought caused by high WT increased in most of the river sections. Notably, in summer, the possibility of environmental drought caused by high WT increased in all river sections. On the other hand, in winter, the possibility of environmental drought caused by low WT increased in most river sections. From the risk map, which quantified the sensitivity of WT to the risk of environmental drought, the river sections Nakbon C, Namgang E, and Nakbon K showed increased stress in the water ecosystem due to high WT when drought occurred in summer. When drought occurred in winter, an increased water ecosystem stress caused by falling WT was observed in the river sections Gilan A, Yongjeon A, Nakbon F, Hwanggang B, Nakbon I, Nakbon J, Nakbon K, Nakbon L, and Nakbon M. The methodology developed in this study will be used in the future to quantify the effects of drought on water quality as well as WT.

H-지수를 이용한 폭염 정량화 및 미래 폭염 전망

서지유(Seo, Jiyu),원정은(Won, Jeongeun),최정현(Choi, Jeonghyeon),이옥정(Lee, Okjeong),김상단(Kim, Sangdan) 한국방재학회 2020 한국방재학회논문집 Vol.20 No.6

전 세계적으로 기온이 상승하면서 일 최고기온 또한 상승하고 있다. 그로 인한 폭염 현상이 증가하고 폭염으로 인한 신체적, 생태계적 피해도 증가하고 있다. 우리나라의 경우 일 최고기온을 통해 폭염을 판단한다. 본 연구에서는 일 최대기온을 이용한H-지수를 산정하여 기상청 ASOS 60개 지점에서의 폭염을 정량화하고자 하였다. 또한 기상청 국가표준 기후변화 시나리오로부터의 미래 기온 정보를 이용하여 미래 H-지수의 변화를 살펴보았다. 연구결과, H-지수를 이용하여 폭염을 정량화하여 폭염거동의 시간적 공간적 변화를 살펴볼 수 있었으며, 미래 H-지수는 현재의 상승추세보다 더 빠르게 증가할 것으로 전망되었다. As global surface air temperature (SAT) rises, the highest daily SAT is also rising. The rise in the highest daily SAT leads to an increase in heat waves, which is turn increases the physical and ecological damage being caused by the heat waves. In Korea, the highest daily SAT is used to determine whether a heat wave has occurred or not. In this study, H-index using the highest daily SAT was calculated to quantify the heat waves at 60 Automated Surface Observing System (ASOS) sites operated by the Korea Meteorological Agency (KMA). The changes in H-index were also investigated using projected future SAT data gathered from KMA s national standard climate change scenarios. As a result, it was possible to investigate the temporal and spatial changes in heat wave behavior by quantifying the heat wave using the H-index. The H-index is expected to increase faster in future than its current upward trend.

폭염사상의 비정상성 빈도해석 및 불확실성 분석

서지유(Seo, Jiyu),원정은(Won, Jeongeun),최정현(Choi, Jeonghyeon),이옥정(Lee, Okjeong),김상단(Kim, Sangdan) 한국방재학회 2021 한국방재학회논문집 Vol.21 No.1

지구 온난화로 인하여 지속적이고 극심한 폭염사상에 대한 우려가 점점 증가되고 있다. 일 최고 기온 관측자료는 강한 비정상성을 나타내고 있으며, 폭염사상의 강도 및 지속기간의 증가가 여러 지역에서 현실화하고 있다. 다양한 지속기간에 대한 폭염사상의 강도를 재현기간과 연관시키는 폭염-지속일수-빈도(Heat wave - Persistence day - Frequency, HPF) 곡선은 폭염사상의 빈도해석을 위한 유용한 도구가 될 수 있다. 본 연구에서는 기후변화에 따른 기온 증가의 경향성을 설명하기 위해 비정상성 HPF 곡선이 개발되고, 그에 대한 불확실성이 분석된다. 비정상성 HPF 모형은 공중보건, 공공안전 및 에너지 관리 분야와 같은 기후변화 적응관리 분야에 활용될 수 있을 것이다. Due to global warming, there is an increasing concern regarding persistent and severe heat waves. The maximum daily surface air temperature observations show strong non-stationary features, and the increased intensity and persistence of heat wave events have been observed in many regions. The heat wave persistence day frequency (HPF) curve, which correlates the intensity of a heat wave persistence event for days with return periods, can be a useful tool to analyze the frequency of heat wave events. In this study, non-stationary HPF curves are developed to explain the trend in the increase of the surface air temperature due to climate change, and their uncertainty is analyzed. The non-stationary HPF model can be used in climate change adaptation management such as public health, public safety, and energy management.

낙동강 유역에서 하천 TP 농도의 공간적 변동성에 영향을 미치는 주요 유역특성

서지유 ( Jiyu Seo ),원정은 ( Jeongeun Won ),최정현 ( Jeonghyeon Choi ),김상단 ( Sangdan Kim ) 한국물환경학회(구 한국수질보전학회) 2021 한국물환경학회지 Vol.37 No.3

It is important to understand the factors influencing the temporal and spatial variability of water quality in order to establish an effective customized management strategy for contaminated aquatic ecosystems. In this study, the spatial diversity of the 5-year (2015 - 2019) average total phosphorus (TP) concentration observed in 40 Total Maximum Daily Loads unit-basins in the Nakdong River watershed was analyzed using 50 predictive variables of watershed characteristics, climate characteristics, land use characteristics, and soil characteristics. Cross-correlation analysis, a two-stage exhaustive search approach, and Bayesian inference were applied to identify predictors that best matched the time-averaged TP. The predictors that were finally identified included watershed altitude, precipitation in fall, precipitation in winter, residential area, public facilities area, paddy field, soil available phosphate, soil magnesium, soil available silicic acid, and soil potassium. Among them, it was found that the most influential factors for the spatial difference of TP were watershed altitude in watershed characteristics, public facilities area in land use characteristics, and soil available silicic acid in soil characteristics. This means that artificial factors have a great influence on the spatial variability of TP. It is expected that the proposed statistical modeling approach can be applied to the identification of major factors affecting the spatial variability of the temporal average state of various water quality parameters.

인공위성 원격 감지 자료를 활용한 산림지역의 생태학적 가뭄 가능성에 대한 확률론적 평가

원정은,서지유,강신욱,김상단,Won, Jeongeun,Seo, Jiyu,Kang, Shin-Uk,Kim, Sangdan 한국수자원학회 2021 한국수자원학회논문집 Vol.54 No.9

Climate change has a significant impact on vegetation growth and terrestrial ecosystems. In this study, the possibility of ecological drought was investigated using satellite remote sensing data. First, the Vegetation Health Index was estimated from the Normalized Difference Vegetation Index and Land Surface Temperature provided by MODIS. Then, a joint probability model was constructed to estimate the possibility of vegetation-related drought in various precipitation/evaporation scenarios in forest areas around 60 major ASOS sites of the Meteorological Administration located throughout Korea. The results of this study show the risk pattern of drought related to forest vegetation under conditions of low atmospheric moisture supply or high atmospheric moisture demand. It also identifies the sensitivity of drought risks associated with forest vegetation under various meterological drought conditions. These findings provide insights for decision makers to assess drought risk and develop drought mitigation strategies related to forest vegetation in a warming era.

기후정보와 지리정보를 결합한 계층적 베이지안 모델링을 이용한 재현기간별 일 강우량의 공간 분포 및 불확실성

이정훈,이옥정,서지유,김상단,Lee, Jeonghoon,Lee, Okjeong,Seo, Jiyu,Kim, Sangdan 한국수자원학회 2021 한국수자원학회논문집 Vol.54 No.10

Quantification of extreme rainfall is very important in establishing a flood protection plan, and a general measure of extreme rainfall is expressed as an T-year return level. In this study, a method was proposed for quantifying spatial distribution and uncertainty of daily rainfall depths with various return periods using a hierarchical Bayesian model combined with climate and geographical information, and was applied to the Seoul-Incheon-Gyeonggi region. The annual maximum daily rainfall depth of six automated synoptic observing system weather stations of the Korea Meteorological Administration in the study area was fitted to the generalized extreme value distribution. The applicability and reliability of the proposed method were investigated by comparing daily rainfall quantiles for various return levels derived from the at-site frequency analysis and the regional frequency analysis based on the index flood method. The uncertainty of the regional frequency analysis based on the index flood method was found to be the greatest at all stations and all return levels, and it was confirmed that the reliability of the regional frequency analysis based on the hierarchical Bayesian model was the highest. The proposed method can be used to generate the rainfall quantile maps for various return levels in the Seoul-Incheon-Gyeonggi region and other regions with similar spatial sizes.

수문학적 추적 기반의 GI 시설 평가 모델 : 생태저류지, 침투도랑, 투수성포장, 식생수로를 대상으로

원정은(Jeongeun),서지유(Won･,Jiyu Seo),최정현(Jeonghyeon Choi),김상단(Sangdan Kim) 한국습지학회 2021 한국습지학회지 Vol.23 No.1

도시 개발로 인한 영향을 최소화하여 물 순환 체계를 개선하기 위해서는 적극적인 강우유출수 관리가 필수적이다. 최근에는 도시의강우유출수 관리를 위한 저영향개발(Low Impact Development, LID) 기법이 합리적인 대안으로 주목받고 있다. Storm Water Management Model(SWMM)은 LID 모듈을 통해 다양한 GI(Green Infra) 시설에 대한 모의 기능을 제공하고 있어 도시 물순환개선 사업에 적극 활용되고 있다. 그러나 SWMM을 이용하여 GI 시설을 모의하기 위해서는 복잡한 유역 설정과 GI 시설 배치에많은 어려움이 존재한다. 본 연구에서는 GI 시설의 핵심적인 수문 프로세스를 구현하면서도 상대적으로 간단하게 GI 시설의 성능을평가할 수 있는 모형이 제안된다. 제안된 모형은 수문학적 추적을 기반으로 작동되므로 GI 시설의 침투, 저류, 증발산을 모두 반영할수 있을 뿐만 아니라 GI 시설에 의한 도시 물순환 개선 효과를 정량적으로 평가할 수 있다. 제안된 모형의 결과와 SWMM의 결과를비교함으로써 제안된 모형의 적용성을 검증하였다. 더붙여서 SWMM의 투수성 포장 모의에서 발생되는 오류에 대한 논의가 포함된다. Active stormwater management is essential to minimize the impact of urban development and improve the hydrological cycle system. In recent years, the Low Impact Development (LID) technique for urban stormwater management is attracting attention as a reasonable alternative. The Storm Water Management Model (SWMM) is actively used in urban hydrological cycle improvement projects as it provides simulation functions for various GI (Green Infra) facilities through its LID module. However, in order to simulate GI facilities using SWMM, there are many difficulties in setting up complex watersheds and deploying GI facilities. In this study, a model that can evaluate the performance of GI facilities is proposed while implementing the core hydrological process of GI facilities. Since the proposed model operates based on hydrological routing, it can not only reflect the infiltration, storage, and evapotranspiration of GI facilities, but also quantitatively evaluate the effect of improving urban hydrological cycle by GI facilities. The applicability of the proposed model was verified by comparing the results of the proposed model with the results of SWMM. In addition, a discussion of errors occurring in the SWMM s permeable pavement system simulation is included.

기계학습기법을 이용한 부산-울산-경남 지역의 증발수요 가뭄지수 예측

이옥정,원정은,서지유,김상단,Lee, Okjeong,Won, Jeongeun,Seo, Jiyu,Kim, Sangdan 한국수자원학회 2021 한국수자원학회논문집 Vol.54 No.8

Drought is a major natural disaster that causes serious social and economic losses. Local drought forecasts can provide important information for drought preparedness. In this study, we propose a new machine learning model that predicts drought by using historical drought indices and meteorological data from 10 sites from 1981 to 2020 in the southeastern part of the Korean Peninsula, Busan-Ulsan-Gyeongnam. Using Bayesian optimization techniques, a hyper-parameter-tuned Random Forest, XGBoost, and Light GBM model were constructed to predict the evaporative demand drought index on a 6-month time scale after 1-month. The model performance was compared by constructing a single site model and a regional model, respectively. In addition, the possibility of improving the model performance was examined by constructing a fine-tuned model using data from a individual site based on the regional model.

도시지역 원격 모니터링 데이터를 활용한 물순환 정보 해석방안

원정은(Jeongeun Won),서지유(Jiyu Seo),최정현(Jeonghyeon Choi),김상단(Sangdan Kim) 대한환경공학회 2022 대한환경공학회 학술발표논문집 Vol.2022 No.11