• Journal of Korea Water Resources Association
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• v.34 no.6
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• pp.673-685
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• 2001

In this study, the drought indicator is calculate from the rainfall, daily highest temperature, streamflow and Palmer Drought Severity Index(PDSI) for water plan and drought management in a relatively wide region. Three levels of drought severity, called drought watch, drought warning, and drought emergency, are established for these series which determine exceedance levels. The 25% nonexceedance level is used for drought watch, 10% for drought warning, and 5% for drought emergency to figure how well the drought indicators represent the past-drought and that those can be used for drought monitoring. As a result, 9-month and 12-month precipitation, and PDSI series shows the best consistency and high correlation indicate droughts. Because the results are based on the gauged data and simply calculated, the suggested indices can be used for basic data for drought monitoring system of a basin.

• Journal of Korea Water Resources Association
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• v.47 no.5
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• pp.435-446
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• 2014

Various drought indices developed from previous studies can not consider the inherent uncertainty of drought because they assess droughts using a pre-defined threshold. In this study, to consider inherent uncertainty embedded in monthly streamflow data, Hidden Markov Model (HMM) based drought index (HMDI) was proposed and then probabilistic assessment of hydrologic drought was performed using HMDI instead of using pre-defined threshold. Using monthly streamflow data (1966~2009) of Pyeongchang river and Upper Namhan river provided by Water Management Information System (WAMIS), applying the HMM after moving-averaging the data with 3, 6, 12 month windows, this study calculated the posterior probability of hidden state that becomes the HMDI. For verifying the method, this study compared the HMDI and Standardized Streamflow Index (SSI) which is one of drought indices using a pre-defined threshold. When using the SSI, only one value can be used as a criterion to determine the drought severity. However, the HMDI can classify the drought condition considering inherent uncertainty in observations and show the probability of each drought condition at a particular point in time. In addition, the comparison results based on actual drought events occurred near the basin indicated that the HMDI outperformed the SSI to represent the drought events.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3B
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• pp.243-252
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• 2011

The change of rainfall pattern due to recent climate change increases the occurrence probability of drought in Korea. Unlike other natural disasters, a drought has long duration, extensive area subject to damage, and greater socioeconomic damage than other disasters. In order to evaluate drought severity, meteorological drought indices are mainly used in practice. This study presents a more realistic method to evaluate drought severity considering drought climate factors as well as socioeconomic factors which are vulnerable to disaster. To perform a spatial evaluation of drought risk in Gyeongsang-do, drought risk was defined and analyzed through the hazard index and the vulnerability index. The drought hazard index was spatially assessed using the drought index and GIS. The drought vulnerability index was also spatially assessed using the 5 socioeconomic factors. As a result, the drought risks were compared and used for evaluating regional drought risk considering regional characteristics of Gyeongsang-do.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.3
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• pp.1-14
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• 2019

North Korea has frequently suffered from extreme agricultural crop droughts, which have led to food shortages, according to the Food and Agriculture Organization (FAO). The increasing frequency of extreme droughts, due to global warming and climate change, has increased the importance of enhancing the national capacity for drought management. Historically, a meteorological drought index based on data collected from weather stations has been widely used. But it has limitations in terms of the distribution of weather stations and the spatial pattern of drought impacts. Satellite-based data can be obtained with the same accuracy and at regular intervals, and is useful for long-term change analysis and environmental monitoring and wide area access in time and space. The Evaporative Stress Index (ESI), a satellite-based drought index using the ratio of potential and actual evaporation, is being used to detect drought response as a index of the droughts occurring rapidly over short periods of time. It is more accurate and provides faster analysis of drought conditions compared to the Standardized Precipitation Index (SPI), and the Palmer Drought Severity Index (PDSI). In this study, we analyze drought events during 2015-2017 in North Korea using the ESI satellite-based drought index to determine drought response by comparing with it with the SPI and SPEI drought indices.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.4B
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• pp.203-211
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• 2012

Once drought occurs, it results in the extensive affected area and considerable socio-economic damages. Thus, it is necessary to assess drought risk and to prepare its counterplans. In this study, using various observation data on meteorological and socio-economical factors, drought risk was evaluated in South Korea. To quantify drought risk, Drought Hazard Index (DHI) was calculated based on the occurrence probability of drought, and Drought Vulnerability Index (DVI) was computed to reflect socio-economic consequences of drought. Drought Risk Index (DRI) was finally suggested by combining DHI and DVI. These indices were used to assess drought risk for different administrative districts of South Korea. The overall results show that the highest drought risk area was Jeolla Province where agricultural practice is concentrated. The drought risk map proposed in this study reflects regional characteristics, thus it could be utilized as a basic data for the establishment of drought preventive measures.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.178-178
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• 2023

Drought and flooding have historically coexisted in Korea, occurring at different times and with varying cycles and trends. The drought indicators measured were (PDSI), (SPI), and (SPEI) in order to statistically analyze the annual or periodic drought occurrence and objectively evaluate statistical characteristics such as the periodicity, tendency, and frequency of occurrence of droughts in the Doam watershed. To compute potential evapotranspiration (PET), both Thornthwaite (Thor) and Penman-Monteith (PM) parameterizations were considered, and the differences between the two PET estimators were analyzed. Hence, SPIs 3 and SPIs 6 revealed a tendency to worsen drought in the spring and winter and a tendency to alleviate drought in the summer in the study area. The seasonal variability trend did not occur in the SPIs 12 and PDSI, as it did in the drought index over a short period. As a result of the drought trend study, the drought from winter to spring gets more severe, in addition to the duration of the drought, although the periodicity of the recurrence of the drought ranged from 3 years to 6 years at the longest, indicating that SPIs 3 showed a brief time of around 1 year. SPIs 6 and SPIs 12 had a term of 4 to 6 years, and PDSI had a period of roughly 6 years. Based on the indicators of the PDSI, SPI, and SPEI, the drought severity increases under climate change conditions with the decrease in precipitation and increased water demand as a consequence of the temperature increase. Therefore, our findings show that national and practical measures are needed for both winter and spring droughts, which happen every year, as well as large-scale and extreme droughts, which happen every six years.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.168-168
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• 2020

This study is to evaluate the drought-related bigdata characteristics published from South Korean by developing crawler. The 5 years (2013 ~ 2017) drought-related posted articles were collected from Korean internet search engine 'NAVER' which contains 13 main and 81 local daily newspapers. During the 5 years period, total 40,219 news articles including 'drought' word were found using crawler. To filter the homonyms liken drought to soccer goal drought in sports, money drought economics, and policy drought in politics often used in South Korea, the quality control was processed and 47.8 % articles were filtered. After, the 20,999 (52.2 %) drought news articles of this study were classified into four categories of water deficit (WD), water security and support (WSS), economic damage and impact (EDI), and environmental and sanitation impact (ESI) with 27, 15, 13, and 18 drought-related keywords in each category. The WD, WSS, EDI, and ESI occupied 41.4 %, 34.5 %, 14.8 %, and 9.3 % respectively. The drought articles were mostly posted in June 2015 and June 2017 with 22.7 % (15,097) and 15.9 % (10,619) respectively. The drought news articles were spatiotemporally compared with SPI (Standardized Precipitation Index) and RDI (Reservoir Drought Index) were calculated. They were classified into administration boundaries of 8 main cities and 9 provinces in South Korea because the drought response works based on local government unit. The space-time clustering between news articles (WD, WSS, EDI, and ESI) and indices (SPI and RDI) were tried how much they have correlation each other. The spatiotemporal clusters detection was applied using SaTScan software (Kulldorff, 2015). The retrospective and prospective cluster analyses were conducted for past and present time to understand how much they are intensive in clusters. The news articles of WD, WSS and EDI had strong clusters in provinces, and ESI in cities.

• Atmosphere
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• v.23 no.1
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• pp.113-121
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• 2013

The objective of this study is to develop and evaluate the system to produce the real-time ensemble drought prediction data. Ensemble drought prediction consists of 3 processes (meteorological outlook using the multi-initial conditions, hydrological analysis and drought index calculation) therefore, more processing time and data is required than that of single member. For ensemble drought prediction, data process time is optimized and hardware of existing system is upgraded. Ensemble drought data is estimated for year 2012 and to evaluate the accuracy of drought prediction data by using ROC (Relative Operating Characteristics) analysis. We obtained 5 ensembles as optimal number and predicted drought condition for every tenth day i.e. 5th, 15th and 25th of each month. The drought indices used are SPI (Standard Precipitation Index), SRI (Standard Runoff Index), SSI (Standard Soil moisture Index). Drought conditions were determined based on results obtained for each ensemble member. Overall the results showed higher accuracy using ensemble members as compared to single. The ROC score of SRI and SSI showed significant improvement in drought period however SPI was higher in the demise period. The proposed ensemble drought prediction system can be contributed to drought forecasting techniques in Korea.

• Journal of The Korean Society of Agricultural Engineers
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• v.49 no.6
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• pp.21-33
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• 2007

Different vegetation indices from satellite images have been used for monitoring drought damages, and this study aimed to develop a drought index using NOAA/AVHRR NDVI(Normalized Difference Vegetation Index) and to analyze the temporal and spatial distribution of spring drought severity in North Korea from 1998 to 2001. A new drought index, DevNDVI(Deviation of NDVI), was defined as the difference between a monthly NDVI and average monthly NDVI at the same cover area, and the DevNDVI images at all years except for 2001 demonstrated the drought-damaged areas referred from various domestic and foreign publications. The vegetation of 2001 showed high vitality despite the least amount of rainfall among the target years, and the reason was investigated that higher temperature above normal average would shift the growing stages of plants ahead. Therefore, complementary methods like plant growth models or ground survey data should be adopted in order to evaluate drought-induced plant stress using satellite-based NDVI and to make up far the distortion induced by other environments than lack of precipitation.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.1
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• pp.21-29
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• 2019

This study analyzed the variability of drought risk based on trend analysis of dry-seasonal dam inflow located in upper river basins. To this, we used areal averaged precipitation and dam inflow of three upper river dams such as Soyang dam, Chungju dam, and Andong dam. We employed Mann-Kendall trend analysis and change point detection method to identify the significant trends and changing point in time series. Our results showed that significant decreasing trends (95% confidence interval) in dry-seasonal runoff rates (= dam inflow/precipitation) in three-dam basins. We investigated potential causes of decreasing runoff rates trends using changes in potential evapotranspiration (PET) and precipitation indices. However, there were no clear relation among changes in runoff rates, PET, and precipitation indices. Runoff rate reduction in the three dams may increase the risk of dam operational management and long-term water resource planning. Therefore, it will be necessary to perform a multilateral analysis to better understand decreasing runoff rates.