**6. Conclusions**

**Figure 10.** Time plot of the mean groundwater level in the optimization scenarios 1 – 3.

**Figure 11.** Time plot of input 1 (exploitation in a certain region) and output 5 (groundwater level at a defined point)

in the optimization scenarios 1 – 3.

44 Water Supply System Analysis - Selected Topics

In this paper an optimal control approach as a component of a decision support system (DSS) for the management of the total water resources (surface water, groundwater, external water resources) in a fast developing region under a critical water shortage has been pre‐ sented. It has been proven that in spite of the large area which has to be managed and the corresponding complex surface and groundwater models the optimization problem could be solved in an appropriate computation time (~ minutes). This could be achieved by a dras‐ tic reduction of the complex groundwater model to a state space model of relatively low di‐ mension (n < 50). The user (i.e. water allocation decision maker) is enabled to select from a number of predefined performance criteria as well as to assign constraints to the elements of the water allocation system in order to specify the management targets according to his/her needs. The performance of the proposed concept is demonstrated by close to reality optimi‐ zation scenarios, whereby the benefit of a new strategic channel has been investigated with a planning horizon of 5 years. Actually the developed DSS component is used in a first ver‐ sion by the decision makers. Future work will focus on the application and adaptation of the developed concept and software for the water resources management of further regions with critical water shortage.
