# Assessing Groundwater Level with a Unified Seasonal Outlook and Hydrological Modeling Projection
## 4 Results and Discussion
### Groundwater Table According to Seasonal Rainfall Outlooks  
Figure 7 illustrates all 3 month groundwater outlooks at the Xinpu well station from January to October in 2018. The simulation parameters were adopted on the basis of the above validation results. Furthermore, in this study, only monthly pumping data were available. Thus, 3000 cmd of pumping rate for the registered well at Xinpu Station was used for our simulation. In Figure 7, the blue dots represent the results of groundwater level simulation according to the rainfall observation from gauges. The red rectangles and green triangles of Figure 7 are the results of groundwater level simulation as the 25 th and 75 th percentiles from seasonal rainfall forecasts, respectively. The simulation results using observation data demonstrate that they corresponded with the groundwater measurement. In other words, the parameters used in the study used were adequate, as they could reasonably reflect the variation of the groundwater table. In Tables 3 and 4, the total forecast rainfall in terms of the 25 th to 75 th percentiles ranged from 331.0 to 423.0 mm for the first seasonal rainfall outlook from January to March at the Guanxi station. The real rainfall occurrence (471.5 mm) was within the forecast interval (277.8 mm and 477.7 mm). A similar situation occurred for the 3 month rainfall outlook from January to March at the Xinpu station. The value of simulated groundwater levels fit the observation values quite well from January to March in 2018, as shown in Figure 7a. Since the precipitation forecasts overestimated the real rainfall occurrence for the second to fifth seasonal rainfall outlooks from February-April to May-July, the groundwater levels during these periods were also overestimated, as indicated in Figure 7b-e. Regardless of the underestimation of rainfall at the Guanxi station and the overestimation of rainfall at the Xinpu station in the sixth seasonal rainfall outlook, the simulation revealed a comparable result to the observation from June to August in 2018. In fact, the above results are also presented in Figure 7f-h. The result of the groundwater simulation, which took the rainfall from the gauges as the inputs, corresponded with the observation result, showing the applicability of this simulation. However, even though the rainfall amounts for both stations were underestimated, such as in Figure 7g,h, the overall simulations of groundwater table corresponded to the observation result because of the high rainfall during this period where the observation water table was 60.333 m; the simulation result was 60.513 m and the 25 th-75 th percentiles of the simulated rainfall-induced water table were 60.465 m-60.814 m, as shown in Figure 7g. In Figure 7h, the observation rainfall-induced groundwater level was 59.788 m, while the simulation result was 59.859 m and the 25 th-75 th percentiles of simulated rainfall were 60.365 m-60.518 m. Therefore, the groundwater generated by seasonal forecast was comparable to the real groundwater table during the raining season. As shown in Figure 7i,j, the result of groundwater table according to the seasonal forecast was higher than the observation result. This was caused by the overestimation of these two gauges, which resulted in a high groundwater level. Figure 7: All 3 month groundwater outlooks from January to March 2018 through October to December 2018: (**a**) January to March; (**b**) February to April; (**c**) March to May; (**d**) April to June; (**e**) May to July; (**f**) June to August; (**g**) July to September; (**h**) August to October; (**i**) September to November; (**j**) October to December. Note that the horizontal axis indicates the simulation time, and the vertical axis represents the groundwater levels. The black lines represent the observations; the blue dashed lines denote the simulation results using real rainfall data; the green triangles and red squares indicate the simulation results using forecast rainfall at the 25 th and 75 th percentiles, respectively.