A Process-based Modeling Approach for Surface Water/Groundwater ...

A Process-based Modeling Approach for Surface Water/Groundwater Interaction and Integrated Watershed Management Jeremy S. Kobor1 and Matt O’Connor1 The existing regulatory framework in California tends to compartmentalize water by considering different portions of the hydrologic cycle separately with different agencies applying different rules for surface water and groundwater resources. In contrast, watersheds function through a series of complex interactions between all components of the hydrologic cycle. One of the primary barriers to achieving policy changes that move towards integrated watershed management is the perception that we don’t have the necessary tools for evaluating watershed processes in a holistic manner. While traditional approaches have focused on evaluating surface water and groundwater resources separately, physicallybased, distributed, hydrologic models such as MIKE SHE are capable of considering the hydrologic cycle as a whole and of simulating the interactions between surface water and groundwater. The increasing availability of GIS datasets describing the topographic, soil, vegetation, hydrologic, and hydrogeologic characteristics of a watershed along with monitoring data describing rainfall, streamflow, and groundwater elevations permit the application of these models in many areas with relatively limited collection of new data. The MIKE SHE model combines a distributed hydrologic model with a 1-dimensional hydraulic model and a 3-dimensional finite-difference groundwater model and simulates surface water/groundwater interaction based on a physical description of water-level-gradient-driven exchanges modulated by aquifer hydraulic conductivity and streambed conductance terms. Here we present a recent application of the model in two Russian River tributary watersheds Atascadero/Green Valley Creek and Dutch Bill Creek. The model was developed to assist in habitat restoration planning focused on achieving recovery of endangered salmonid populations. Simulating the spatial variability of groundwater recharge and baseflow generation was a key component in applying the model to classify stream reaches based on low-flow water availability conditions relative to habitat requirements. Various changes in groundwater pumping and streamflow diversion regimes were simulated in order to develop strategies for maintaining and improving low-flow habitat conditions. This project serves as an example of utilizing integrated numerical models to effectively manage surface water and groundwater as interconnected resources. 1

O’Connor Environmental, Inc., 447 Hudson St., Healdsburg, CA 95448, (707) 431-2810, [email protected]

Jeremy Kobor Mr. Kobor is an expert in the application of numerical hydrologic, hydraulic, and sediment transport models. He has more than twelve years of professional experience working on a wide range of projects related to flood hazard mitigation, habitat restoration, water supply and climate change adaptation planning, and integrated surface water/groundwater management.