In California and many other countries and jurisdictions, surface waters have historically been regulated as if they were unconnected to groundwater. Yet in reality, surface waters and groundwater are often hydrologically connected. Many of the rivers that support fisheries are hydrologically dependent on tributary groundwater to maintain instream flow. This means that when there is an intensive pumping of tributary groundwater, the result can be reductions in instream flow and damage to fisheries.

Consider the Scott River in Northern California, part of the larger Klamath River basin, where nearby groundwater contributes to the Scott River. When high volumes of groundwater are extracted from nearby wells, it depletes the Scott River’s instream flow with adverse impacts on salmon and steelhead trout.1 This has led to litigation over the application of California public trust law to groundwater extraction affecting Scott River instream flows, and efforts to use California’s Sustainable Groundwater Management Act (SGMA) to ensure that groundwater pumping near the Scott River is compatible with the instream flow needs of fisheries. Situations similar to the Scott River surface and groundwater basin are unfolding throughout California.