Design of an Optimal Compliance Monitoring Network and Feedback Information for Adaptive Management of Saltwater Intrusion in Coastal Aquifers

Abstract

Management strategies for the optimal and sustainable use of groundwater resources are developed based on prescriptive models that use mathematical tools for simulation and optimization together with field data. Because of the uncertainty inherent in the groundwater systems, it is essential to verify the compliance of the implemented strategies to those prescribed by using proper monitoring techniques during and after the implementation stages of the groundwater management project. In this work, an adaptive management approach for optimal management and monitoring of coastal aquifers is proposed. A simulation-optimization approach is used to derive optimal pumping strategy for the management of saltwater intrusion in coastal aquifers. Then, an optimal monitoring network is designed to evaluate the compliance of the aquifer responses in the field with those predicted by the simulation-optimization model. The designed network can be used to monitor the compliance in the field in terms of the salinity concentration levels, which result from the implementation of the optimal pumping strategy. Uncertainty in the values of groundwater parameters and the uncertainty resulting from the deviation of the pumping strategies from the prescribed optimum values are characterized by considering different realizations of these values in the three-dimensional density dependent flow and transport simulation model. A new objective for monitoring is considered in this study. The objective function consists of maximizing the coefficient of variation of the salinity concentration at the monitored locations and minimizing the correlation coefficient between the concentrations at the monitored locations. Using this objective, the monitoring locations are chosen in regions where the uncertainty in the concentration values is highest, and those locations where the correlation between the concentrations of the monitored locations is lowest, so that the redundancy in monitoring data is the least. The concentration data collected at the optimal compliance monitoring locations can be used as feedback information to improve the initially developed optimal coastal aquifer management strategies. The sequential modification of the optimal pumping strategies in stages is illustrated using numerical experiments.