Numerical issues in management of stream/aquifer interactions

Groundwater pumping in the vicinity of streams can produce significant reductions in streamflow and adverse impacts on ecosystems. Modeling and management techniques can be useful to control this problem. This paper focuses on the use of optimization based management models for problems in which the interaction between streams and aquifers is a central concern. A formulation that couples optimization algorithms with established simulation models for groundwater and stream flow is described. The nonlinear response of stream stage and streamflow to groundwater pumping is investigated with an example aquifer/stream system. It is found that nonlinearity arises both from the dependence of stream stage on streamflow and from the changes in stream/aquifer connection.