The aim of optimization in this sub-project is to define rules for the management of scarce groundwater resources under different scenarios. With multi-objective optimization, it is possible to optimize groundwater management not only with regard to one objective but to consider several different objectives that contradict each other in their fulfilment (for example, high abstraction rates vs. low decrease in groundwater levels). The optimization process results in several solutions each suggesting different groundwater management rules. These solutions represent the best possible compromises between contradictory objectives, taking into account pre-defined preferences.

Figure 1: Schematic outline of the multi-criteria optimization process

Simulation-based optimization offers the most realistic description of an aquifer and the conditions under which it is managed. The groundwater model that is being developed at the TU Berlin is used to simulate the processes occurring in the aquifer, while a connected optimization algorithm continuously makes suggestions for improved management strategies (figure 1).

In order to compensate for surpluses or deficits in groundwater abstraction that may occur spatially or temporally, additional alternative water sources (seawater desalination, wastewater treatment, groundwater recharge, etc.) or the redistribution of extracted water are being considered during the optimization process.

Groundwater abstraction wells in the catchment area of the aquifer are combined into groups. Monthly varying withdrawals are generalized as withdrawal patterns (how withdrawal rates change over time). These can then be changed by adjusting basic parameters (figure 2).

Figure 2: Dividing the multi-criteria optimization process into two optimization “problems”

First results

We have been working on a comprehensive program solution to connect the optimization algorithms to MODFLOW, so that different management scenarios can be processed. We are currently working with local stakeholders to implement local management rules in the optimization algorithm. Furthermore, the stakeholders will define preferences that must be taken into account during the optimization process. With this work done, the next step will be to optimize groundwater management under different scenarios.