# Rainfall Standard of Disaster Prediction for Agricultural Droughs in S. Korea
## 3 Results  
Setting Up Reference Points for Rainfall in View of Disaster Prevention Relevant to Agricultural Droughts  
We set up the reference points for disaster-prevention rainfall relevant to agricultural droughts by comparatively analyzing the average rainfall with and without agricultural drought damage, respectively, by municipality and year. An integrated standard of disaster reduction rainfall was proposed by analyzing the difference in annual rainfall for municipalities. Based on the days when agricultural drought damage occurred from 1965 to 2018 in South Korea, we calculated the past average annual rainfall to derive the final average rainfall per municipality. For the years without agricultural drought damage, we calculated the average annual rainfall per municipality, to derive the final average rainfall. We analyzed the average rainfall, both with and without agricultural droughts, respectively, per municipality, as shown in Figure 7.  
Figure 6: Setting up rainfall for disaster prediction relevant to agricultural droughts. Across the municipalities, agricultural drought damage occurred when the average annual rainfall was 1199 mm (min 913 mm-max 1704 mm). Agricultural drought damage did not occur when the average rainfall was 1297 mm (min 1063 mm-max 1631 mm). It was determined that the annual average rainfall of agricultural drought damage is about 100 mm less than the whole country's average rainfall. We analyzed the average rainfall trend lines, both with and without agricultural droughts, respectively, in each municipality, as shown in Table 4. Based on the municipalities' rainfall-trend lines, with drought damage and the average rainfall trend lines analyzed, the agricultural drought occurred in South Korea when the municipalities recorded nearly 100 mm below the average annual rainfall. However, the average rainfall in Daejeon, Sejong and Jeju Island was smaller than the amount of rainfall in agricultural drought damage. Average rainfall for agricultural drought damage was \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Region Index**} & \multicolumn{2}{c}{**Average Rainfall (mm)**} & \multirow{2}{*}{**2\(-\)1)**} \\ \cline{2-3}  & **Agricultural Drought Damage** & & \\ \hline GW & 1156 & 1335 & 179 \\ GG & 1123 & 1335 & 212 \\ GN & 1275 & 1369 & 94 \\ GB & 1036 & 1110 & 75 \\ GJ & 1213 & 1357 & 145 \\ DG & 913 & 1063 & 150 \\ DJ & 1412 & 1252 & \(-\)160 \\ BS & 1088 & 1481 & 393 \\ SE & 1092 & 1393 & 301 \\ SJ & 1638 & 1218 & \(-\)420 \\ US & - & 1272 & - \\ IC & 973 & 1230 & 257 \\ JN & 1202 & 1313 & 111 \\ JB & 1126 & 1254 & 129 \\ JJ & 1704 & 1631 & \(-\)73 \\ CN & 1127 & 1237 & 110 \\ CB & 1086 & 1203 & 117 \\ \hline Average & 1199 & 1297 & 101 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Analysis of disaster-prevention rainfall of municipality. Figure 7: Setting up rainfall for disaster prevention relevant to agricultural droughts by municipality. calculated a year ago based on the time of drought occurrence. In Daejeon and Sejong, the reason why the amount of rainfall in agricultural drought damage was higher than the average annual rainfall was one and two times. The rainfall for drought damage in 2018 was 1548 mm in Daejeon and 1638 mm in Sejong, and many rainfalls occurred from July to December 2017. On Jeju Island, rainfall is relatively high because it is located on the coast: 1974 mm in 2013 and 1876 mm in 2016, and the rainfall is the same in the previous year. Despite the occurrence of agricultural drought damage in the three regions, the annual rainfall for agricultural drought damage was high due to the occurrence of large rainfall in the previous year, and the average rainfall increased due to the less frequent occurrence of agricultural drought. However, in Daejeon, Sejong and Jeju Island, the frequency of agricultural droughts is low, and less than 3% of the total area of Korea is expected to have a small impact on the whole country.