# Rainfall Standard of Disaster Prediction for Agricultural Droughs in S. Korea
## 4 Discussion  
In the past, previous studies on drought predicted and evaluated drought by using the drought index [17; 18]. Moreover, Prediction of drought using drought index is widely used in many fields, and its applicability has been reviewed [9; 10; 51; 52; 53]. However, previous studies validated the analysis of droughts only with hydrologic parameters, hardly paying attention to the damage from droughts or quantitatively analyzing the rainfall leading to droughts, to propose the reference points for preventing disasters or ending droughts. In Korea, the drought prediction using the drought index is based on meteorological drought prediction using SPI6 only in the Korea Meteorological Administration among the various ministries. The Ministry of Environment, Ministry of Ministry of Agriculture, Food and Rural Affairs, and Ministry of the Interior and Safety, which manage drought, make drought \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Year**} & **Agricultural Drought Relief Rainfall** & \multirow{2}{*}{**Year**} & **Agricultural Drought Relief Rainfall** \\  & **(mm)** & & **(mm)** \\ \hline
1965 & 140 & 1977 & 149 \\
1966 & 141 & 1978 & 149 \\
1967 & 142 & 1981 & 152 \\
1968 & 142 & 1982 & 152 \\
1969 & 143 & 1994 & 161 \\
1970 & 144 & 1995 & 161 \\
1971 & 144 & 2013 & 174 \\
1972 & 145 & 2015 & 176 \\
1973 & 146 & 2016 & 176 \\
1975 & 147 & 2017 & 177 \\
1976 & 148 & 2018 & 178 \\ \hline \multicolumn{3}{c}{Average} & \multicolumn{2}{c}{154} \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Analysis of disaster-reduction rainfall by year considering linear regression analysis. prediction through observational data. The drought index is used as a reference for drought prediction. Therefore, this study analyzed rainfall of disasters prediction for in local governments across the country, not the drought index, for agricultural droughs in Korea. In disaster management, drought should first determine the presence or absence of drought occurrence, using observational data, and second, assess the depth of drought, using the drought index. In addition, when evaluating the depth of drought, it is necessary to prepare for drought by using a drought index suitable for each department's characteristics. We collected the cases of damage from agricultural droughs that had occurred in South Korea from 1965 to 2018 and analyzed the impacts of the damage from droughs by municipality and year. A total of 22 agricultural droughs devastated an area of 90,631 ha, causing crops to fail and wilt across 108 regions (min 5977 ha-max 470,423 ha). Furthermore, we analyzed the rainfall in each municipality, based on the data from 68 KMA-led rainfall observatories, and calculated the rainfall by applying the area ratios of the Thiessen's polygon. In South Korea, the average annual rainfall from 1965 to 2018 was 1271 mm, with min 882 mm and max 1860 mm rainfall forming a non-linear curve repeatedly rising and falling. Moreover, South Korea's monthly rainfall was characterized by monsoonal fronts built in summer with 65% of the country's total annual rainfall concentrated in June to September. In this study, we focused on agricultural droughs, calculated the average rainfall leading to droughs by municipality and year, and established integrated reference points for disaster prevention. Furthermore, we calculated the average monthly rainfall for droughs to end by municipality and year, and established integrated reference points of rainfall for disaster reduction. The rainfall standard for disaster prediction that can judge agricultural drought in disaster management was established. The findings in this study involved the reference points based on the limited past damage from agricultural droughs, that is, the disaster-prevention and disaster-reduction rainfall based on average annual and monthly rainfall, respectively. In South Korea, agricultural droughs mostly occur from June to September and end within three to four months, as the country's drought season overlaps with its monsoon season.