Do groundwater management plans work? Modelling the effectiveness of groundwater management scenarios

In contrast to management optimisation methods, which quantify decision variables to create plans, this study does not seek the “best” strategy. Instead, it simulates the sequential decision-making process implicit in environmental management, so that the effectiveness of management scenarios, when implemented as intended, can be evaluated. The purpose was to develop a methodology to quantitatively evaluate the effectiveness of groundwater management plans by simulating sequential management decisions that evolve based on aquifer/management feedback. A groundwater management scheme was structured as a system control loop to capture the aquifer/management feedback, and management decisions were based on realistically sparse observation times and locations. The method indicates how a plan may proceed in reality under alternate timings and frequencies of management decisions and in systems with differing response times. A synthetic example quantified the impact of a generic plan, specifying environmental objectives, extraction restrictions and entitlement limits (maximum volume/year that users are permitted), relative to no-management by combining a numerical model of “reality” with management rules under a stochastic climate. The management decision-making frequency varied from daily to decadal. Generally, effectiveness decreased as the interval between management interventions increased and intervals greater than annual showed minimal improvement compared to entitlement only. The timing of management decisions relative to the irrigation season also impacted plan effectiveness, and when decisions were made prior to the irrigation season, quarterly management was less effective than annual and biannual management. By testing the capacity of plans to achieve objectives, groundwater management can be systematically and objectively improved.