• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.3
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• pp.77-88
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• 2019

Drought is the recurrent natural disasters which harshly affect agricultural production and society in various parts in Bangladesh. Information on the spatiotemporal variability of drought events plays a vital role to take necessary action towards drought mitigation and sustainable development. This study aims to analyze the spatial and temporal variation of meteorological drought in Bangladesh during 1981-2015 using Effective Drought Index (EDI). Monthly precipitation data for 36 years (1980-2015) were obtained from 27 meteorological stations. Drought frequency (DF) and areal extent of drought were considered to investigate the spatiotemporal structure of drought. The DF analysis showed that the northern, southwestern and central regions of the country are comparatively vulnerable to meteorological drought. The frequency of drought in all categories has considerably increased during the recent five years from 2011 to 2015. Furthermore, the most significant increasing trend of the drought-affected area was found over the central region especially for pre-monsoon (March-May) season during this period while the decreasing trend of the affected area was found within the eastern region during the study period. To prevent and mitigate the damages of drought disasters in Bangladesh, agricultural and government managers should pay more attention to those regional drought events that occur in pre-monsoon season. The outcome of the present study can be used as explanatory data in building the strategies to drought monitoring and mitigation activities in Bangladesh.

• Journal of The Korean Society of Agricultural Engineers
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• v.63 no.5
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• pp.95-105
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• 2021

Drought is a disaster that causes prolonged and wide scale damage. Recently, the severity and frequency of drought occurrences, and drought damage have been increased significantly due to climate change. As a result, a quantitative study of drought factors is needed to better understand and prevent future droughts. In the case of agricultural drought, several existing studies examine the economic damage caused by droughts and their causes, but these studies are not well suited to estimating crop-oriented agricultural drought damage and the factors that absolutely affect agricultural drought. This study determines which factors most affect agricultural drought. It examines meteorological factors and those related to agricultural water supplied by irrigation facilities. Rice paddy production per unit area is lower than the average from the last two years where agricultural drought occurred. We compare the relative frequency of agricultural drought impacts with irrigation facilities, effective reservoir storage, the number of water supply facilities, and the meteorological drought index such as Standardized Precipitation Index (SPI). To identify factors that affect agricultural drought, we correlate rice paddy production anomalies with irrigation water supply for the past two years. There was a high positive correlation between rice paddy production and irrigation water usage, and there was a low or moderate negative correlation between rice paddy production anomalies compared to the average of the past two years and SPI. As a result, agricultural water supply by irrigation facilities was judged to be more influential than meteorological factors in rice paddy production. This study is expected to help local governments establish policies related to agricultural drought response.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.143-143
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• 2021

Climate change indicators, mainly frequent drought which has happened since the drought of 1994, 1995, and 2012 causing the devastating effect to the agricultural sector, and could be more disruptive given the context of climate change indicators by increasing the temperature and more variable and extreme precipitation. Changes in frequency, duration, and severity of droughts will have enormous impacts on agriculture production and water management. Since both the possibility of drought manifestation and substantial yield losses, we are propositioning an integrated method for evaluating past and future agriculture drought hazards that depend on models' simulations in the Hung-up watershed. to discuss the question of how climate change might influence the impact of extreme agriculture drought by assessing the potential changes in temporal trends of agriculture drought. we will calculate the temporal trends of future drought through drought indices Standardized Precipitation Evapotranspiration Index, Standardized Precipitation Index, and Palmer drought severity index by using observed data of (1991-2020) from Wonju meteorological station and projected climate change scenarios (2021-2100) of the Representative Concentration Pathways models (RCPs). expected results confirmed the frequency of extreme agricultural drought in the future projected to increase under all studied RCPs. at present 100 years drought is anticipated to happen since the result showing under RCP2.6 will occur every 24 years, RCP4.5 every 17 years, and RCPs8.5 every 7 years, and it would be double in the largest warming scenarios. On another side, the result shows unsupportable water management, could cause devastating consequences in both food production and water supply in extreme events. Because significant increases in the drought magnitude and severity like to be initiate at different time scales for each drought indicator. Based on the expected result that the evaluating the impacts of extreme agricultural droughts and recession could be used for the development of proactive drought risk management, policies for future water balance, prioritize sustainable strengthening and mitigation strategies.

• Journal of Korea Water Resources Association
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• v.30 no.1
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• pp.55-62
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• 1997

To quantitatively investigate the nationwide drought characteristics and to comparatively evaluate the 1994-1995 drought with several past droughts of significant magnitude regional frequency analysis is made for the meteorological stations in each of the 47 subbasins covering the whole nation. With monthly precipitation data for the period of records at the stations in each subbasin low precipitation data series of various durations are formulated with the running totals of monthly data and fitted to probability distributions. The method of L-method of L-moments is used to determine the unbiased parameters of each distribution, and using the best-fit distribution for each subbasin the low precipitations of various durations with return periods of 5, 10, 20, 30, and 50 years are estimated. The drought frequency maps are drawn with the low drought frequency analysis the drought of 1994-1995 is evaluated in its severity and areal extent in comparison with four other past drought of significance. The current practice of safety standards for the design of impounding facilities is also evaluated with reference to the recurrence interval of the severe drought, and a recommendation is made for the future design standard.

• Journal of The Korean Society of Agricultural Engineers
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• v.66 no.5
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• pp.29-40
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• 2024

Most agricultural reservoirs were built between the 1940s and 1970s. Therefore, it is necessary to evaluate the current water supply safety, considering changes in water capacity, the water management, and environment in relation to the passage of time.. The design frequency of drought, the number of years areservoir needs to be able to withstand a drought phenomenon, foragricultural water resources in Korea is the 10-year drought. As the water supply system and water supply patterns change, it is necessary to establish a concept of water supply reliability, which refers to the stability of water supply. This study evaluated the water supply reliability of agricultural reservoirs based on the designed frequency. The previously designed frequency and water balance analysis were used to calculate and analyze reservoir storage capacity, water supply turnover, water supply amount, water supply potential, water utilization safety, and water supply reliability. As a result, Yongmyeon Reservoir was found to be stable in terms of water supply reliability, whereas Seongho and Yongpung Reservoirs were found to be unstable using all methods. In particular, when converting the water utilization safety and the water supply reliability to the frequency of drought, Seongho and Yongpung Reservoir were in the lowest class, with a frequency of drought less than four years. Thus, we recommend that the consideration of water supply reliability be included in the preparation of adaptive measures and water supply strategies as changes in environmental conditions continue to develop.

• Journal of Korea Water Resources Association
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• v.46 no.4
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• pp.425-437
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• 2013

This study performed the bivariate drought frequency analysis for duration and severity of drought, using copula functions which allow considering the correlation structure of joint features of drought. We suggested the confidence intervals of duration-severity-frequency (DSF) curves for the given drought duration using stochastic scheme of monthly rainfall generation for 57 sites in Korea. This study also investigated drought risk via illustrating the largest drought events on record over 50 and 100 consecutive years. It appears that drought risks are much higher in some parts of the Nakdong River basin, southern and east coastal areas. However, such analyses are not always reliable, especially when the frequency analysis is performed based on the data observed over relatively short period of time. To quantify the uncertainty of drought frequency curves, the droughts were filtered by different durations. The 5%, 25%, 50%, 75%, and 95% confidence intervals of the drought severity for a given duration were estimated based on the simulated rainfall time series. Finally, it is shown that the growing uncertainties is revealed in the estimation of the joint probability using the two marginal distributions since the correlation coefficient of two variables is relatively low.

• Journal of Korea Water Resources Association
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• v.48 no.12
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• pp.1011-1021
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• 2015

This study aims to investigate droughts from the magnitude perspective based on the SPI (Standardized Precipitation Index) and the theory of runs applicable to quantitative analysis of drought in South Korea. In addition, the dry spell analysis was conducted on the drought history in the five major river basins of South Korea to obtain the magnitude, duration and severity of drought, and the quantitative evaluation has been made on historical droughts by estimating the return period using the SDF (Severity-Duration-Frequency) curve gained through drought frequency analysis. The analysis results showed that the return periods for droughts at the regional and major river basin scales were clearly identified. The return periods of severe drought that occurred around the major river basins in South Korea turn out to be mostly 30 to 50 years with the years of the worst drought in terms of severity being 1988 and 1994. In particular, South Korea experienced extremely severe droughts for two consecutive years during the period between 1994 and 1995. Drought in 2014 occurred in the Han River basin and was evaluated as the worst one in terms of severity and magnitude.

• Journal of Korea Water Resources Association
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• v.39 no.9 s.170
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• pp.745-754
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• 2006

This study adopted the Rectangular Pulses Poisson Process Model for the drought severity-duration-frequency analysis to characterize the spatial pattern of drought over the Korean peninsula using the rainfall data of the 59 rain gauge stations. First of all, the drought severity in the southern part of the Korean peninsula was found to be generally high for any return period. This result is consistent for both cases with and without considering the overlap probability of rectangular pulses, which is also valid for longer durations. Comparison with those of observed drought frequency and maximum severity also showed that the result in this study has enough reliability.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.5
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• pp.1871-1885
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• 2013

In this study, spatio-temporal distribution of future drought in South Korea was predicted by using the meteorological data generated from GCMs on which a variety of climate changing scenarios are applied. Drought phenomena was quantitatively analyzed using SPI(Standardized Precipitation Index). In addition, potential drought hazard maps for different drought duration and return period were made for the South Koreaby drought frequency analysis after deriving SDF(Severity-Duration-Frequency) curves using the 54 weather stations throughout the country. From the potential drought hazard maps, drought is expected to be severer in Nakdong River basin and Seomjin River basin under A2 scenario. It was also predicted that drought would be severe in the Han River basin by RCP8.5 scenario. In the future, potential drought hazard area would be expanded until the Eastern part of Nakdong River basin as compared with that of past under A2 scenario condition. Research results indicated that future drought would be extensively occurred all areas of South Korea not limiting in the southern part of country.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.3
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• pp.387-393
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• 2018

Considering the effect of climate change, a quantitative analysis of extreme drought is needed to reduce the damage from extreme droughts. Therefore, in this study, a quantitative risk analysis of extreme drought was conducted. The threshold level method was applied to define a drought event using Cheugugi rainfall data in past, gauged rainfall data in present, and climate change scenario rainfall data in future. A bivariate drought frequency analysis was performed using the copula function to simultaneously consider two major drought characteristics such as duration and severity. Based on the bivariate drought frequency curves, the risks for the past, present and future were calculated and the risks for future extreme drought were analyzed comparing with the past and present. As a result, the mean drought duration of the future was shorter than that of past and present, however, the mean drought severity was much larger. Therefore short term and severe droughts were expected to occur in the future. In addition, the analysis of the maximum drought risk indicated that the future maximum drought risk was 1.39~1.94 times and 1.33~1.81 times higher than the past and present. Finally, the risk of extreme drought over past and present maximum drought in the future was very high, ranging from 0.989 to 1.0, and the occurrence probability of extreme drought was high in the future.