Interdisciplinary Modeling of the Socioeconomic Tradeoffs of Water Management in River Basins with Potential for Disconnection between Surface and Groundwater

Abstract:

There is mounting evidence that the impacts of groundwater declines on streamflow are widespread and that environmental flow limits will be reached in many watersheds with groundwater pumping. In these contexts, a convergent approach using integrated and interdisciplinary models built upon detailed understanding of hydrologic, ecological, and socioeconomic processes can help quantify system tradeoffs, thus facilitating the resolution of conflicts associated with water management decisions. While groundwater pumping is crucial for agricultural production, it can also diminish streamflow that provides habitat for fish, creating a tradeoff involving several underlying hydro-physical and temporal system complexities. First, groundwater pumping can draw down the water table to a point where there is a sudden and permanent vertical disconnection in seepage between the river surface water and underlying aquifer. Second, the intra-annual benefits of water use vary significantly among and within water users, especially for agricultural producers during different crop life stages and for fishery growth rates during specific spawning periods. These complexities and their implications for the two-way interactions between hydrologic, ecological, and socioeconomic systems have not been incorporated in existing integrated models. We build an integrated model consisting of hydrologic, ecological, and socioeconomic sub-models to explore the implications of these system complexities on the tradeoffs that emerge. Using Scott Valley in California as our study system, we simulate tradeoff curves for agricultural production and fishery growth, while explicitly modeling the potential for disconnection between surface and groundwater, and estimating the marginal gains of modified pumping schedules at a sub-annual timescale. We compare these pumping schedules to those from a baseline scenario to reveal the long term consequences of ignoring these system dynamics.