## 5 Conclusions  
The objectives of the study are to characterize the behavior of SGIs in the PPGB and quantify the influence of such interactions induced by the landforms and anthropogenic activities. The interactions between surface water and groundwater have been assessed based on the GSFLOW model. The study conducts model calibration and validation by using observations from January 2015 to December 2017. The influences of wet and dry seasons on the SGIs are quantified based on the calibrated and validated model. An artificial recharge lake located in the upstream region of the Linien River is assessed to quantify the impact of the water resource infrastructure on the local water cycle. Results of calibration and validation have demonstrated that the coupled groundwater and surface water model can reproduce well the dynamics of the water interactions in the PPGB. Calibration results show that the differences between observed groundwater data and simulated solutions are limited to \(\pm 1\) m. Simulations also show good agreement between the river flow observations and the solutions from the GSFLOW model. In general, the dry and wet seasons yield groundwater levels varying from 2 to 20 m. The groundwater variations are significant in the downstream area of the PPGB. The substantial differences in groundwater levels in the wet and dry seasons are obtained in the river upstreams in the PPGB. The differences of the averaged hydraulic heads in the wet and dry seasons can vary over 4 m, indicating the high impact of the wet and dry seasons on the groundwater variations. The water budgets show that over 80% of the precipitation is from the wet seasons in the PPGB. The average infiltration is approximately 40% of total precipitation, and the surface runoff is about  
Figure 15: The simulated volumetric fluxes of water cycle components based on the presence of an artificial recharge lake in the simulation area. Note that the values with black and blue colors represent the simulated flow rates without and with the artificial lake. 57% of the total precipitation. The water from the soil zones to the unsaturated zones is involved in the overall behavior of the infiltration. In the PPGB, the volumetric flux from the soil zones to the unsaturated zones is 4% of the total infiltration on average. The surface runoff, interflow, and net groundwater discharge provide approximately 70%, 20%, and 10% volumetric flow to the streamflow, respectively. The interflow in the water cycle plays an essential role in the river system in the entire PPGB. The average interflow rate is approximately \(1.65\times 10^{6}\) m\({}^{3}\)/d. The flux of the interflow rate in the wet seasons is 200% more than that in the dry seasons. In the PPGB, a large amount of interflow has motivated a different type of water usage in many areas near the rivers. The average flow rates of most water cycle components in the downstream fan area are higher than those in the upstream fan area. In the upstream fan area, only the average flow rate of the soil zones to the unsaturated zones is higher than that in the downstream fan area. The observations of the precipitation from 2015 to 2017 have shown that the upstream fan received relatively less average precipitation as compared to the data obtained for the downstream fan area. However, the relatively high permeability of toposils in the upstream fan can lead to the high flux of the vertical flow from the soil zones to the unsaturated zones. By counting the performance of water fluxes for the unit area, we obtain relatively strong interactions of the water cycle in the upstream fan area. Such interactions are obviously near rivers and indicate high impacts between groundwater and surface water systems in the upstream fan area. In the study, the case with an artificial recharge lake is represented by an additional HRU in the GSFLOW model. Because of the relatively small area, the contribution of the recharge lake on the water budgets is insignificant.