THE USE OF INTEGRATED MODELING TO UNDERSTAND THE ROLE OF GROUNDWATER – SURFACE WATER INTERACTIONS IN WATER MANAGEMENT DECISION MAKING

This study analyzes the impact of groundwater surface water interactions on water management decisions using a fully integrated physical hydrology model. Many basins across the world rely on conjunctive use; yet most of the modeling tools currently applied in the management framework make simplifications in both physics and interactions. We seek to understand the implications of this approach and its inherent assumptions in the context of real world decision making. This study incorporates management algorithms from the Water Evaluation and Planning (WEAP) model with an integrated hydrology model, ParFlow, to simulate water management operations for several test domains. ParFlow is a fully coupled physical hydrology model capable of simulating groundwater surface water interactions in heterogeneous porous media. Richards’ equation is used for variably saturated subsurface flow and the diffusive wave equation is applied for overland flow. The common land model (CLM), which is coupled to ParFlow, simulates land surface processes. Test domains are designed to include irrigation and municipal demands supplied by both groundwater and surface water supplies for a variety of aquifer configurations. Management decisions are evaluated using several multi-year simulations and results are compared between the integrated ParFlow model and a simple management model with no physical processes. Differences highlight the sensitivity of management decisions to groundwater surface water interactions.