• Journal of Korea Water Resources Association
• /
• v.50 no.1
• /
• pp.65-73
• /
• 2017

This study analyzed the peak drought severity and drought duration of the Cheongmicheon watershed from 1985 to 2015 to assess the lag time of peak drought severity between several drought indices. Standardized Precipitation Index (SPI) based on precipitation and Standardized Precipitation Evapotranspiration Index (SPEI) based on precipitation and evapotranspiration were applied as meteorological drought indices. Streamflow Drought Index (SDI) based on runoff data was applied as hydrological drought index. In case of SDI, we used Soil and Water Assessment Tool (SWAT) model for simulation of daily runoff data. As a result, the time of peak drought severity of SDI occurred after the occurrence of SPI and SPEI. The lag time for the peak drought severity, on average, between SDI and SPI was 0.59 months while SDI and SPEI was 0.79 months. As compared with SDI, the maximum delay was 2 months for both SPI and SPEI. This study results also shows that even though the rainfall events were able to cope with meteorological droughts, they were not always available to solve the hydrological droughts in the same time.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.5
• /
• pp.1851-1860
• /
• 2013

The Standardized Precipitation Index (SPI) is widely applied to evaluate for meteorological droughts. However, the SPI is limited to capture a drought event with a short duration, expecially shorter than one month. In this study, we proposed a daily SPI (DSPI) as a way to overcome the limitation of the monthly SPI for drought monitoring. In order to objectively assess the ability of the drought reproduction of the DSPI, we performed a receiver operating characteristic (ROC) analysis using the quantified drought records from official reports, newspapers, etc. The results of ROC analysis showed that the DSPI has an ability to reproduce short-term drought compared with other indices. It also showed that the main cause of historical droughts was the shortage of rainfall accumulated during the time period less than 90 days compared with the rainfall of normal years.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2006.05a
• /
• pp.1166-1171
• /
• 2006

Drought is defined by differently for the several scientific and technical fields such as hydrological drought, agricultural drought, meteorological drought, climatological drought, atmospheric drought. A lot of drought indices have been developed to quantify drought severity levels. However these drought indices might be expressed differently as the drought conditions for specific period because the drought severity level is using different types of data on each condition. It is necessary for development of quantative drought representation methods by drought index application. In this research, the reaction to the historical droughts is analyzed after estimation of PDSI, SPI and MSWSI(Modified Surface Water Supply Index) in south korean territory. Lastly the drought representation methods were examiner combining the drought indices by drought indices. The arithmetic mean drought indices that include PDSI, SPI, in yearly basis from 1971 to 2001 and MSWSI in yearly basis from 1974 to 2001 were estimated through the whole nation. The applicability of drought indices are examined based on the observed drought data for national and regional droughts. The result shows that PDSI, SPI(3), SPI(6), and MSWSI have proven to be sensitive enough to the historical drought. The correlation analysis of each drought index was conducted whether they could show the long and short term drought equally. The analysis of how appropriately represent for the historical drought was used for determining for the combined drought index. Consequently, PDSI, SPI(3), SPI(6), and MSWSI have been appeared as suitable indices for the development of quantitative drought representation methods. For the decision of weight on combining PDSI, SPI(3), SPI(6), and MSWSI, drought map was made for eighteen alternative to decide weight. The results showed that PDSI(20%), SPI(3)(60%), SPI(6)(10%), and MSWSI(10%) have been the most well matched weights. Using selected weights of each drought indices and by reconstructing the national mean drought severity on yearly basis, the fact that the year of historical drought is in accordance with the verified one for drought representation. In short, the acquired technique using combined drought index can be used for useful and believable quantitative method of drought analysis.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.36 no.1
• /
• pp.135-141
• /
• 2016

This study aims to analyze the feasibility of installing a storage facility and make recommendations based on a cost-benefit analysis regarding the installation of a storage facility capable of preventing both floods and droughts. The capacity and installation costs are specified for the storage facility necessary to prevent floods, and a cost-benefit analysis is conducted by calculating the costs and benefits for each cost or benefit factor such as loss amounts, recovery costs, and drought prevention. The information can be used as the basic data for suggesting the feasibility of installing a multipurpose storage facility capable of preventing floods and droughts simultaneously. Also, this study expects to utilize its detailed results in a number of different ways including the prediction of loss amounts from natural disasters.

• Journal of Korean Society of Water and Wastewater
• /
• v.34 no.5
• /
• pp.335-344
• /
• 2020

Due to global climate change, mega-droughts have occurred frequently. Since long-term droughts make it difficult to secure the water resources, water supply needs to be restricted in a reasonable manner. In the event of limited water supply, the waterworks need to develop a restricted water supply strategy. This study showed that analyzing daily water supply could be used to respond to the first stage of a drought. According to an analysis of Korea's major water authorities, there was about 7~21% of room for daily minimum water supply in case of a drought. Restricting the water supply by lowering pressure is a good strategy for local water authorities with high water leakage rate since leakage is inversely dependent with pressure. For this method, it is necessary to quantify water deficiency and pressure at each node using a simulation. Since DDA-based software is not possible to predict changes in demand at nodes with pressure reduction, WaterGEMS, a PDA software, was used to quantitatively predict water shortages and pressures at each node. Locations where water is deficient need to install booster pumps or to be dispatched with water tank truck and bottled water. Without these support, lowering pressure could not be an option for water works. This paper suggests a method for waterworks to plan a drought by lowering pressure to restrict water supply using daily water supply analysis and PDA based simulation.

• Atmosphere
• /
• v.22 no.2
• /
• pp.199-208
• /
• 2012

This study was conducted in order to analyze weather characteristics during the reign of King Sejo in the Chosun Dynasty based on The Annals of the Chosun Dynasty. For this purpose, first of all, we need to determine whether The Annals of the Chosun Dynasty is a reliable material for research on weather characteristics. Thus, we compared weather phenomena during the reign of King Sejo with those in China and Japan in the same period. From the results, it was found that The Annals of the Chosun Dynasty is a useful material at least to grasp macroscopic trends in weather phenomena. Based on this assumption, we analyzed weather characteristics during the reign of King Sejo using data from The Annals of the Chosun Dynasty. During the days of King Sejo, the climate was not changed violently and there were not many disasters caused by abnormal climate such as bad harvests. This suggests that the climate was relatively stable during the period of King Sejo. As a consequence of stable weather, famine decreased markedly. However, this was not only because of stable climate but also because of the government's active efforts to reduce disasters. As droughts and floods were not frequent, social costs for recovery from disasters also decreased considerably and the saved money could be invested in the construction of social safety nets for the prevention of disasters. One of factors supporting the enthronement of King Sejo was a series of heavily damaging bad harvests during the reign of Kings Munjong and Danjong. The prevention of bad harvests was a historical mission given to the regime of King Sejo. During his reign, King Sejo promoted various policies in order to stop bad harvests. Such efforts included the government's active construction of embankments, introduction of seeds suitable for reclaimed lands, and inspiration of the consciousness of forceful farming enduring natural disasters such as floods. As a result, abnormal weathers such as floods and droughts did not lead directly to bad harvests.

• Korean Journal of Agricultural Science
• /
• v.43 no.2
• /
• pp.258-274
• /
• 2016

Recently, as fluctuations in annual precipitations continue to grow, the frequency of floods and droughts is rapidly increasing. Especially, since many reservoirs are reported as having less capacity and aging faster than large dams, the damages due to floods and droughts are estimated to become more severe. With this background for the present study, field investigation of reservoirs in Chungnam, Chungbuk, and Chonbuk regions was carried out for disaster prevention and the safety management of agricultural reservoirs. Furthermore, embankment transformations were compared and analyzed after the raising of embankments. Based on design methods for remodeling agricultural reservoirs and the results of embankment raising and the problems which occurred on crest, supplementation to the upstream and downstream slopes, control sector, and spillway should be implemented in the existing reservoir. In regard to this, the condition assessment score of compound member of reservoirs was performed, the Chungnam region score was in the 3.11-4.73 range. In addition, reservoirs in Chungbuk scored in the 4.00-4.49 range, and reservoirs in Chonbuk scored in the 3.90-4.60 range. Applying current precision safety inspection practices to small reservoirs requires economic expenses and time, for which assessment items are too varied and complex. Therefore, subdivided condition assessment items and criteria should be improved and streamlined by deleting, reducing, combining, and selecting only the riskiest factors. In the future, reservoirs should be periodically monitored and systemically managed and rational plans for maintenance and repairs should be used as reinforcement methods.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2011.05a
• /
• pp.373-373
• /
• 2011

Korean Government has been promoting Four River Restoration Project (i.e., Han, Geum, Nakdong, and Yeongsan rivers) since the second half of 2008. This project is expected to protect against floods and droughts by water resources management. Many researchers have study water resources management, but most studies were focused on direct runoff. However, in order to efficiently protect against floods and droughts, baseflow should be studied as well as direct runoff. Because baseflow has a great effect on streamflow, it needs to be correctly analyzed. For more accurate analysis of baseflow, direct runoff and baseflow from streamflow should be separated first. In this study, 12 flow gauging stations of four major rivers were selected, and flow data from them were obtained (2004-2010) through WAMIS and Web-based SWAT Bflow system (http://www.envsys.co.kr/~swatbflow) which was used to separate direct runoff and baseflow. Baseflow values of Pass 2 in SWAT Bflow system were used. As a result of this study, baseflow contribution was ranged from 23.4% to 68.6% and accounted for about 50% of streamflow. Through this study, it shows that in the case of the flow fluctuation, baseflow is more affected than direct runoff by changes in streamflow in a flood or dry season. Thus, baseflow estimation should not be overlooked for efficient water resources management. However, it has a limitation in this study that because this study used to select randomly 12 flow gauging stations, it did not show a common tendency on each watershed. It is important that flow gauging stations reflected on topographic characteristics of each watershed should be selected in a rigorous manner for further reliable and accurate baseflow estimation on four major rivers.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.40 no.2
• /
• pp.209-215
• /
• 2020

In order to understand the characteristics of natural droughts, it is very important to interpret the spatio-temporal relationship between different types of droughts. In this study, meteorological and hydrological drought events were defined to account for the overlap between drought duration and spatial extent in three dimensions (i.e., latitude, longitude, and timing). In other words, the spatio-temporal drought propagation characteristics were analyzed based on the drought characteristic factors (duration, area, depth, center). The drought map considering the characteristics of spatio-temporal drought propagation can be used to find the fundamental cause of the hydrological drought which is expected to frequently occur in the future. In addition, the drought map is expected to be useful in preparing an effective drought response plan.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.40 no.2
• /
• pp.135-143
• /
• 2020

Natural drought is a three-dimensional phenomenon that simultaneously evolves in time and space. To evaluate the link between meteorological and hydrological droughts, we defined a drought event from a three-dimensional perspective and analyzed the propagation characteristics in time and spaces. Overall results indicated that 77 % of the total cases of spatio-temporal droughts was propagated based on the single category relationship between meteorological and hydrological drought events, while 23 % was affected by multiple meteorological drought events to the occurrence of hydrological drougts. Especially, it turned out that the hydrological drought was caused by the spatio-temporal effects of the propagation of four meteorological drought events generated due to long-term lack of precipitation in 1994-1995. In addition, the meteorological drought caused by the lack of precipitation in the summer of 2001 lasted for several months, and was propagated to the hydrological drought in April 2002.