Regulation of groundwater through the use of management plans is becoming increasingly prevalent as global groundwater levels decline. But seldom are plans systematically and quantitatively assessed for effectiveness. Instead, the state of an aquifer is commonly considered a proxy for plan effectiveness despite being a combination of many drivers.
Groundwater management under uncertainty is challenging, often provisional and experimental, and for this research, was structured as a systems control problem. This enabled development of an assessment rubric to determine whether groundwater management plans have the required features that allow plan effectiveness to be quantitatively tested.
The rubric was applied to 15 Australian groundwater management plans and only 47% were found to be testable [White et al., 2016]. However, testability does not indicate plan effectiveness and testable plans do not necessarily achieve planned objectives. To numerically quantify the effectiveness of groundwater management, the impact of extraction restrictions was probabilistically assessed by simulating management of a simple unconfined groundwater system using MODFLOW [McDonald, 1984] and Flopy[Bakker et al., 2016]. Water managers were privy only to head levels in a varying number of grid cells assigned as monitoring wells, and used that limited information to make allocation decisions at each time step. Extraction rates for each simulated management period were determined based upon the observed heads from the previous management period and adjusted depending upon triggers outlined in the management plan. The effectiveness of water restrictions as a management technique for the purpose of maintaining supply reliability under various decision making frequencies, aquifer response times and climate scenarios was explored.
It is crucial that groundwater management plans be effective, and in order to determine their effectiveness, we need to start testing them.