• Journal of Korea Water Resources Association
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• v.50 no.12
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• pp.863-875
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• 2017

In this study, the effects of potential evapotranspiration method on drought index results were evaluated using SC-PDSI. Monthly heat index method, Penman-Monteith method, and Hargreaves equation were used as potential evapotranspiration method. SC-PDSI was calculated using three potential evapotranspiration method at 56 stations and compared the results. As a result, it was confirmed that the results by Penman-Monteith method and Hargreaves equation showed similar SC-PDSI calculation results without much difference, and the result by monthly heat index method showed a relatively large difference. It was confirmed that the results of SC-PDSI and drought situation judgment for the period of spring and winter season showed a big difference by the month. In conclusion, when calculating PDSI in Korea, using Penman-Monteith method and Hargreaves equation will be able to express the drought situation well.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.82-82
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• 2021

전 세계적으로 가뭄은 농업·식량안보·수자원관리·생태계 등 다양한 분야에서 부정적인 영향을 미치고 있다. 일반적으로 가뭄은 강수량의 부족으로 발생하고, 지표수와 지하수의 가용성이 제한됨에 따라 작물생산 및 사회·경제적으로 피해가 발생한다. 이러한 영향은 특정 가뭄 모니터링 및 조기 경보와 관련하여 가뭄 지표를 결정할 때 중요한 고려사항이다. 가뭄을 분석하기 위해서는 가뭄 지표를 적용하여 정확하게 반영하고 나타내는 것이 중요하다. 가뭄의 특성을 객관적으로 정량화하기 어렵기 때문에 다양한 지표와 계산을 통한 가뭄 모니터링 및 분석 기술이 필요하며, 강수량, 토양수분, 증발산량 및 식생과 관련하여 가뭄 지표가 개발되었다. 본 연구에서는 혼합 가뭄 지표 (Drought Indicator Blends) 활용하여 우리나라의 가뭄을 분석하였다. 혼합 가뭄 지표는 NOAA (National Oceanic and Atmospheric Administration)의 기후 예측 센터 (Climate Prediction Center, CPC)에서 여러 가뭄 지수를 단기 또는 장기로 구분하여 통합, 개발되었다. 단기 및 장기 혼합 제품은 PDSI (Palmer Drought Severity Index), Z-Index, SPI (Standardized Precipitation Index)를 결합하여 가뭄을 추정한다. 혼합 가뭄 지표는 해당 지역의 단기 및 장기 가뭄을 이해하는데 유용하게 활용할 수 있으며, 현재까지 미국에서 활발하게 연구가 진행되고 있다. 단기 지표는 비관개 농업, 토양수분 등 강수량에 밀접한 관련이 있는 가뭄과 관련되어 평가하며, 장기 지표의 경우 관개 농업, 지하수위 등 장기간 가뭄과 연관성을 가지고 있다. 단기 및 장기 혼합 가뭄 지표를 우리나라에 적용함으로써 기존 단일 가뭄 지수를 활용한 가뭄 분석 이상으로 다방면에서 효율적인 가뭄 모니터링을 할 수 있을 것이라 판단된다.

• Korean Journal of Agricultural and Forest Meteorology
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• v.23 no.4
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• pp.340-348
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• 2021

Continuous monitoring of RGB (Red, Green, Blue) vegetation indices is important to apply remote sensing technology for the estimation of crop growth. In this study, we evaluated the performance of eight vegetation indices derived from soybean RGB images with various agronomic parameters under drought stress condition. Drought stress influenced the behavior of various RGB vegetation indices related soybean canopy architecture and leaf color. In particular, reported vegetation indices such as ExGR (Excessive green index minus excess red index), Ipca (Principal Component Analysis Index), NGRDI (Normalized Green Red Difference Index), VARI (Visible Atmospherically Resistance Index), SAVI (Soil Adjusted Vegetation Index) were effective tools in obtaining canopy coverage and leaf chlorophyll content in soybean field. In addition, the RGB vegetation indices related to leaf color responded more sensitively to drought stress than those related to canopy coverage. The PLS-DA (Partial Squares-Discriminant Analysis) results showed that the separation of RGB vegetation indices was distinct by drought stress. The results, yet preliminary, display the potential of applying vegetation indices based on RGB images as a tool for monitoring crop environmental stress.

• Journal of Korea Water Resources Association
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• v.49 no.4
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• pp.305-314
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• 2016

In this study, a quantitative assessment was carried out in order to identify the agricultural drought in time and space using the Terra MODIS remote sensing data for the agricultural drought. The Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) were selected by MOD13A3 image which shows the changes in vegetation conditions. The land cover classification was made to show only vegetation excluding water and urbanized areas in order to collect the land information efficiently by Type1 of MCD12Q1 images. NDVI and EVI index calculated using land cover classification indicates the strong seasonal tendency. Therefore, standardized Vegetation Stress Index Anomaly (VSIA) of EVI were used to estimated the medium-scale regions in Korea during the extreme drought year 2001. In addition, the agricultural drought damages were investigated in the country's past, and it was calculated based on the Standardized Precipitation Index (SPI) using the data of the ground stations. The VSIA were compared with SPI based on historical drought in Korea and application for drought assessment was made by temporal and spatial correlation analysis to diagnose the properties of agricultural droughts in Korea.

• Journal of Korea Water Resources Association
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• v.54 no.11
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• pp.969-983
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• 2021

Evapotranspiration, one of the hydrometeorological components, is considered an important variable for water resource planning and management and is primarily used as input data for hydrological models such as water balance models. The FAO56 PM method has been recommended as a standard approach to estimate the reference evapotranspiration with relatively high accuracy. However, the FAO56 PM method is often challenging to apply because it requires considerable hydrometeorological variables. In this perspective, the Hargreaves equation has been widely adopted to estimate the reference evapotranspiration. In this study, a set of parameters of the Hargreaves equation was calibrated with relatively long-term data within a Bayesian framework. Statistical index (CC, RMSE, IoA) is used to validate the model. RMSE for monthly results reduced from 7.94 ~ 24.91 mm/month to 7.94 ~ 24.91 mm/month for the validation period. The results confirmed that the accuracy was significantly improved compared to the existing Hargreaves equation. Further, the evaporative demand drought index (EDDI) based on the evaporative demand (E₀) was proposed. To confirm the effectiveness of the EDDI, this study evaluated the estimated EDDI for the recent drought events from 2014 to 2015 and 2018, along with precipitation and SPI. As a result of the evaluation of the Han-river watershed in 2018, the weekly EDDI increased to more than 2 and it was confirmed that EDDI more effectively detects the onset of drought caused by heatwaves. EDDI can be used as a drought index, particularly for heatwave-driven flash drought monitoring and along with SPI.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.6
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• pp.517-526
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• 2018

Climate adaptation strategies for water utilities including 16 water treatment plants(WTPs) in Jeju were investigated. Drought, heat wave, and heavy rain were among the most significant climate factors affecting water utilities in Jeju. Heat wave increases water temperature, which in turn increases the concentration of algae, color, and odor materials. Some adaption strategies for the heat wave can be strengthening water monitoring and introducing advanced water treatments. Heavy rain increases raw water turbidity in surface water. The 7 WTPs that take raw water from streams or springs had a maximum turbidity of less than 50 NTU under heavy rain. However, due to concerns of turbidity spike in treated water, some WTPs discontinued intaking raw water when raw water turbidity increased more than 2 NTU. They instead received treated water from other WTPs which took groundwater for water supply. This happens because of the low skills of employees. Thus, there needs to be an increase in operator competency and upgrade of water facilities for the adaption of heavy rain. To improve adaption for the drought, there should be an increase in the capacity of intake facilities of surface water as well as a decrease in water loss. In addition, water consumption per person should be decreased.

• Korean Journal of Hydrosciences
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• v.8
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• pp.125-136
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• 1997

The simulation techniques of hydrologic data series have develped for the purposes of the design of water resources system, the optimization of reservoir operation, and the design of flood control of reservoir, etc. While the stochastic models are usually used in most analysis of water resources fields for the generation of data sequences, the indexed sequential modeling (ISM) method based on generation of a series of overlapping short-term flow sequences directly from the historical record has been used for the data generation in the western USA since the early of 1980s. It was reported that the reliable results by ISM were obtained in practical applications. In this study, we generate annual inflow series at a location of Hong Cheon Dam site by using ISM method and autoregressive, order-1 model (AR(1)), and estimate the drought characteristics for the comparison aim between ISM and AR(1).

• 한국방재학회:학술대회논문집
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• 2010.02a
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• pp.104-104
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• 2010

지난 2008년 가을부터 시작되어 2009년 봄까지 발생했던 전국적인 극한 가뭄을 계기로 가뭄모니터링의 필요성은 증대되었다. 본 연구는 우리나라에서 가뭄 모니터링을 위한 MODIS 위성영상 자료의 활용을 제안하였다. MODIS 영상은 임의의 지역의 시 공간적 특성을 관찰할 수 있는 해상도를 보유하고 있으며, MODIS에서 제공하는 MOD11(LST: Land Surface Temperature)은 가뭄 발생의 판별에는 유효하나 가뭄 심도와 지속기간을 판단하기 위해서는 기준이 되는 강우량 및 가뭄지수와의 비교가 필요하다고 알려져 있다. 본 연구에서는 MOD11(LST) 위성자료와 EDI(Effective Drought Index) 가뭄지수의 상관성을 고려하여 한반도 가뭄모니터링을 위한 MODIS 위성영상의 활용성을 평가하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.4
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• pp.669-680
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• 2017

This study evaluated the consistency of the standard flow to forecast low-flow based on various drought indices. The data used in this study were streamflow data at the Gurye2 station located in the Seomjin River and the Angang station located in the Hyeongsan River, as well as rainfall data of nearby weather stations (Namwon and Pohang). Using streamflow data, the streamflow accumulation drought index (SADI) was developed in this study to represent the hydrological drought condition. For SADI calculations, the threshold of drought was determined by a Change-Point analysis of the flow pattern and a reduction factor was estimated based on the kernel density function. Standardized runoff index (SRI) and standardized precipitation index (SPI) were also calculated to compared with the SADI. SRI and SPI were calculated for the 30-, 90-, 180-, and 270-day period and then an ROC curve analysis was performed to determine the appropriate time-period which has the highest consistency with the standard flow. The result of ROC curve analysis indicated that for the Seomjin River-Gurye2 station SADI_C3, SRI30, SADI_C1, SADI_C2, and SPI90 were confirmed in oder of having high consistency with standard flow under the attention stage and for the Hyeongsan River-Angang station, SADI_C3, SADI_C1, SPI270, SRI30, and SADI_C2 have order of high consistency with standard flow under the attention stage.

• Korean Journal of Environmental Biology
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• v.41 no.3
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• pp.283-290
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• 2023

The Republic of Korea reclaimed land to increase its food self-sufficiency rate, but the yield was reduced due to abnormal climate. In this study, it was hypothesized that rapid and continuous monitoring technology could help improve yield. Using the vegetation index (VI) analysis, the drought stress index was calculated and the drought stress for corn grown in Hwaong, Saemangeum, and Yeongsan River reclaimed tidal land was predicted according to drying treatment. The vegetation index of corn did not decrease during the last 20 days of irrigation when soil moisture rapidly decreased, but decreased rapidly during the 20 days after irrigation. The reduction rate of the vegetation index according to the drying treatment was in the order of Saemangeum>Yeongsan River>Hwaong reclaimed tidal land, and normalized difference vegetation index(NDVI) decreased by approximately 50% in all reclaimed tidal lands, confirming that drought stress occurred due to the decrease in moisture content of the leaves. In addition, structure pigment chlorophyll index (SIPI) and photochemical reflectance index (PRI), which are calculated based on changes in light use efficiency and carotenoids, were reduced; drought stress caused a decrease in light use efficiency and an increase in carotenoid content. Therefore, vegetation index analysis was confirmed to be effective in evaluating and predicting drought stress in corn growing on reclaimed tidal land corn.