• Journal of Korea Water Resources Association
• /
• v.35 no.5
• /
• pp.597-609
• /
• 2002

This study suggests a methodology of hydrologic decision making for the establishment of a standard of drought management from the drought analysis by the past drought history and for the drought monitoring and management according to drought processing. The construction and analysis of a decision tree diagram are performed and the step by step plan according to drought severity is suggested. Say, the decision tree diagram is constructed by the transition probability and quantity of monthly precipitation. Then the drought processing is investigated by the analysis of diagram and the 3-step of drought notice, drought warning, and emergency plan are established. The suggested methology in this study can be used for the other area and the decision tree diagram be used by changing the diagram according to the utilization purposes. Also, the choice of monthly PDSI class and precipitation analysis can be performed by the continuous data supplement. And so, a new standard value by the modified diagram is provided and the continuous drought management will be possible.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2022.05a
• /
• pp.141-141
• /
• 2022

Drought is a global phenomenon that affects almost all landscapes and causes major damages. Due to non-linear nature of contributing factors, drought occurrence and its severity is characterized as stochastic in nature. Early warning of impending drought can aid in the development of drought mitigation strategies and measures. Thus, drought forecasting is crucial in the planning and management of water resource systems. The primary objective of this study is to make improvement is existing drought forecasting techniques. Therefore, we proposed an improved version of Seasonal Autoregressive Integrated Moving Average (SARIMA) model (MD-SARIMA) for reliable drought forecasting with three years lead time. In this study, we selected four watersheds of Han River basin in South Korea to validate the performance of MD-SARIMA model. The meteorological data from 8 rain gauge stations were collected for the period 1973-2016 and converted into watershed scale using Thiessen's polygon method. The Standardized Precipitation Index (SPI) was employed to represent the meteorological drought at seasonal (3-month) time scale. The performance of MD-SARIMA model was compared with existing models such as Seasonal Naive Bayes (SNB) model, Exponential Smoothing (ES) model, Trigonometric seasonality, Box-Cox transformation, ARMA errors, Trend and Seasonal components (TBATS) model, and SARIMA model. The results showed that all the models were able to forecast drought, but the performance of MD-SARIMA was robust then other statistical models with Wilmott Index (WI) = 0.86, Mean Absolute Error (MAE) = 0.66, and Root mean square error (RMSE) = 0.80 for 36 months lead time forecast. The outcomes of this study indicated that the MD-SARIMA model can be utilized for drought forecasting.

• Journal of Korea Water Resources Association
• /
• v.56 no.12
• /
• pp.929-937
• /
• 2023

This study aims to develop rules for the Determination of Drought Stages at the Local Level based on the drought cases in Gwangju and Jeollanam-do in 2022-2023. Among the eight drought indicators provided, six indicators (Agricultural drought stage (for paddy), Residential & industrial drought stage, SPI-12, Relative agricultural water storage, Residential water consumption change (for domestic use), Residential water consumption change (for non-domestic use) were confirmed to have statistical correlations with the perceptions of local government officials and experts. Additionally, this drought indicator was applied to a decision tree algorithm to develop rules for determining the severity of drought. Although it presented results similar to those of the existing method presented in previous studies, it showed a significant comparative advantage in explaining the temporal and spatial patterns of drought in the Gwangju and Jeollanam-do.

• Journal of Korean Society of Rural Planning
• /
• v.24 no.4
• /
• pp.47-55
• /
• 2018

Currently in the drought evaluation, which is a supplier-oriented standard that applies storage rates of reservoirs, evaluation for users that use agricultural water is not done. Therefore, this study established drought evaluation items for drought evaluation based on farmers' judgement, conducted a survey on farmers and experts, compared and analyzed weighted value between two groups, and then classified the evaluation standards per each evaluation item. The agricultural drought evaluation items are 5 major items of water supply lapse rate, agricultural weather, agricultural irrigation facility, crop and soil, and 12 subsections for regional characteristics and opinions of consumers that use water to be reflected. The result of analyzing weighted value of farmers and experts' major items shows that farmers is agricultural irrigation facility(0.219), water supply lapse rate(0.211), agricultural weather(0.204), crop(0.183) and soil(0.183). Experts is agricultural weather(0.297), agricultural irrigation facility(0.202), water supply lapse rate(0.189), crop(0.162) and soil(0.150), which displays difference between the two groups. The agricultural drought criteria standards are established based on precedent studies and cases, and grades of evaluation items are 1st grade(extreme stage), 2nd grade(warning stage), 3rd grade(alert stage) and 4th grade(attention stage). The above analysis per each consumer-oriented agricultural drought evaluation item and the analysis on the standards of evaluation grades are expected to be used as a basic resource for establishing agriculture drought policy and selecting drought area in the future.

• Journal of Korea Water Resources Association
• /
• v.51 no.11
• /
• pp.1011-1020
• /
• 2018

This study aims to develop a drought monitoring scheme based on groundwater which can be exploit for water supply under drought stress. In this context, groundwater level can be used as a proxy for better understanding the temporal evolution of drought state. First, kernel density estimator is presented in the monthly groundwater level over the entire national groundwater stations. The estimated cumulative distribution function is then utilized to map the monthly groundwater level into the standardized groundwater level index (SGI). The SGI for each station was eventually converted into the index for major cities through the Thiessen polygon approach. We provide a drought classification for a given SGI to better characterize the degree of drought condition. Ultimately, we conclude that the proposed monitoring framework enables a more reliable estimation of the drought stress, especially for a limited water supply area.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2022.05a
• /
• pp.305-305
• /
• 2022

A better approach for assessing meteorological drought occurrences is increasingly important in mitigating and adapting to the impacts of climate change, as well as strategies for developing early warning systems. The present study defines meteorological droughts as a period with an abnormal precipitation deficit based on monthly precipitation data of 18 gauging stations for the Han River watershed in the past (1974-2015). This study utilizes a Bayesian parameter estimation approach to analyze the effects of climate change on future drought (2025-2065) in the Han River Basin using the Coupled Model Intercomparison Project Phase 6 (CMIP6) with four bias-corrected general circulation models (GCMs) under the Shared Socioeconomic Pathway (SSP)2-4.5 scenario. Given that drought is defined by several dependent variables, the evaluation of this phenomenon should be based on multivariate analysis. Two main characteristics of drought (severity and duration) were extracted from precipitation anomalies in the past and near-future periods using the copula function. Three parameters of the Archimedean family copulas, Frank, Clayton, and Gumbel copula, were selected to fit with drought severity and duration. The results reveal that the lower parts and middle of the Han River basin have faced severe drought conditions in the near future. Also, the bivariate analysis using copula showed that, according to both indicators, the study area would experience droughts with greater severity and duration in the future as compared with the historical period.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.39 no.1
• /
• pp.155-163
• /
• 2019

The knowledge about drought propagation is very important in accurate estimation of hydrological drought characteristics and efficient development of early warning system. This study investigated a probabilistic relationship of drought propagation based on Bayesian network model for historic period and for future projection under climate change scenario RCP 8.5 over the Han River basin. The results revealed that the propagation rate and lag time have increasing and decreasing trends from the historic period of 1967-2013 to the future periods of 2014-2053 and 2054-2100 under climate change, respectively. The probabilistic results of Bayesian model revealed that the probability of occurrence of lag time varied spatially and decreased when the intensity of meteorological drought changed from moderate to severe and extreme condition during 1967-2013. The values of probability increased in the first future period of 2014-2053 in several sub-basins and slight decreased in the second period of 2054-2100. The proposed probabilistic results will be useful for the decision makers to develop related policies with an appropriate insight toward the future drought status.

• Journal of Climate Change Research
• /
• v.6 no.1
• /
• pp.55-60
• /
• 2015

Agro-Meteorological Information Service (AMIS) network has been established since 2001 by Rural Development Administration (RDA) in Korea, and has provided access to current and historical weather data with useful information for agricultural activities. AMIS network includes 158 automated weather stations located mostly in farm region, with planning to increase by 200 stations until 2017. Agrometeorological information is disseminated via the web site (http://weather.rda.go.kr) to growers, researchers, and extension service officials. Our services will give enhanced information from observation data (temperature, precipitation, etc.) to application information, such as drought index, agro-climatic map, and early warning service. AMIS network of RDA will help the implementation of an early warning service for weather risk management.

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

• Atmosphere
• /
• v.16 no.4
• /
• pp.269-278
• /
• 2006

Extremely hot weathers may cause major weather-related deaths in the summertime. Influences of heat waves on daily mortalities in 6 major cities of South Korea were investigated. Daily deaths at Seoul were exponentially increased with the daily maximum temperature. However, there were regional differences of the temperature dependence on the mortality because of an acclimation effect of inhabitants. The threshold temperature (with respect to daily maximum temperature) at Seoul was found to be about $31^{\circ}C$ provided that it is determined by a two-phase regression model. The meteorological causes of recordable hot summer in late July of 1994 and their impacts on human health were also investigated. Strong surface heating caused by strong insolation under conditions with clear sky and dry surface due to prolonged drought was likely to be closely associated with the extreme hot weather in 1994 in South Korea.