# Assessing Groundwater Level with a Unified Seasonal Outlook and Hydrological Modeling Projection
## 4 Results and Discussion
### Rainfall Generation by WGEN
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Guanxi Station** & **2018** & **Real Occurrence** & \multicolumn{2}{c}{**25 th Percentile of**} & \multicolumn{2}{c}{**75 th Percentile of**} & \multicolumn{2}{c}{**Seasonal**} \\  & **2018** & **(mm)** & **Simulation Rainfall** & **Simulation Rainfall** & **Forecast A/N/B** & **Hit/Miss** \\ \hline
1 st & Jan. & 267.0 & 55.2 & 55.5 & 10/60/30 & \\ Feb. & Feb. & 147.5 & 101.0 & 154.9 & 10/60/30 & \\ Mar. & 57.0 & 121.6 & 267.3 & 10/60/30 & \\ \hline Total & 471.5 & 277.8 & 477.7 & Hit \\ \hline
2 nd & Feb. & 147.5 & 19.2 & 146.3 & 10/50/40 & \\ Mar. & 57.0 & 232.0 & 237.7 & 20/60/20 & \\ Apr. & 85.5 & 111.0 & 279.2 & 30/50/20 & \\ \hline Total & 290.0 & 362.2 & 663.2 & & Miss \\ \hline
3 rd & Mar. & 57.0 & 120.0 & 353.9 & 20/60/20 & \\ Apr. & 85.5 & 107.9 & 122.1 & 30/50/20 & \\ May & 85.0 & 211.3 & 277.9 & 30/50/20 & \\ \hline Total & 227.5 & 439.2 & 753.9 & & Miss \\ \hline
4 th & Apr. & 85.5 & 233.7 & 326.2 & 20/50/30 & \\ May & 85.0 & 227.5 & 374.0 & 20/50/30 & \\ Jun. & 177.0 & 232.6 & 274.6 & 30/50/20 & \\ \hline Total & 347.5 & 693.8 & 974.8 & & Miss \\ \hline
5 th & May & 85.0 & 240.2 & 355.5 & 10/50/40 & \\ Jun. & 177.0 & 346.0 & 396.5 & 20/50/30 & \\ Jul. & 199.0 & 231.3 & 603.8 & 20/50/30 & \\ \hline Total & 461.0 & 817.5 & 1328.8 & & Miss \\ \hline
6 th & Jun. & 177.0 & 387.6 & 580.6 & 20/50/30 & \\ Jul. & 199.0 & 147.2 & 194.8 & 20/50/30 & \\ Aug. & 659.5 & 139.8 & 274.5 & 20/50/30 & \\ \hline Total & 1035.5 & 674.6 & 1049.9 & & Hit \\ \hline
7 th & Jul. & 199.0 & 190.3 & 249.3 & 30/50/20 & \\ Aug. & 659.5 & 177.7 & 235.0 & 20/50/30 & \\ Sep. & 182.0 & 296.0 & 335.8 & 20/50/30 & \\ \hline Total & 1040.5 & 664 & 820.1 & & Miss \\ \hline
8 th & Aug. & 659.5 & 315.9 & 377.9 & 20/50/30 & \\ Sep. & 182.0 & 117.1 & 361.4 & 20/50/30 & \\ Oct. & 84.5 & 45.3 & 52.6 & 20/50/30 & \\ \hline Total & 926.0 & 478.3 & 791.9 & & Miss \\ \hline
9 th & Sep. & 182.0 & 224.6 & 442.8 & 20/50/30 & \\ Oct. & 84.5 & 55.4 & 114.8 & 10/60/30 & \\ Nov. & 47.5 & 64.7 & 65.9 & 20/50/30 & \\ \hline Total & 314.0 & 344.7 & 623.5 & & Miss \\ \hline
10 th & Oct. & 84.5 & 57.9 & 229.1 & 10/60/30 & \\ Nov. & 47.5 & 8.7 & 29.5 & 10/50/40 & \\ Dec. & 39.0 & 67.2 & 138.2 & 20/60/20 & \\ \hline Total & 171.0 & 133.8 & 376.0 & & Hit \\ \hline \hline \end{tabular} Note: N, normal; B, below normal; A, above normal.  
\end{table} 
Table 3: Ten sets of seasonal rainfall outlooks and real rainfall occurrences of Guanxi station in 2018. This study used the seasonal forecast from CWB to calculate the 25 th to 75 th percentiles of simulated precipitation from WGEN. A comparison between this simulated precipitation and the actual precipitation was made to study the hitting rate. Thus, actual precipitation within the simulated precipitation (25 th-75 th) can represent an accurate prediction. Then, we added up the monthly precipitation to examine whether the annual precipitation at Guanxi and Xinpu station was within the simulated precipitation in terms of 25 th to 75 th percentiles. According to the above results, the annual values of the 25 th and 75 th percentiles of simulated rainfall were within 1921-3285 mm at the Guanxi station. The amount of real rainfall was 2031 mm. This shows that its seasonal rainfall outlook was around 30% accurate for the 3 month forecast, but the total amount of annual rainfall was within the range of 25 th and 75 th percentiles (1921-3285 mm). Similarly, at the Xinpu station, its seasonal rainfall outlook was about 40% accurate in terms of hitting rate, but the amount of annual rainfall (1295 mm)