ICONS: Interconnected Surface Water in the Central Valley

The Navarro River
Navarro River Overlooking view of the Navarro River. © Erin Feinblatt

The ICONS dataset provides information on the depth to groundwater and the likely presence of interconnected surface water (ISW) in the Central Valley. When surface water in rivers and streams is connected to groundwater through a continuously saturated zone, this is called ISW. With ISW, any excessive pumping of groundwater can reduce the surface water supply, impacting nearby vegetation and ecosystems. By understanding this link between surface water and groundwater, and by knowing the locations of likely ISW, groundwater sustainability agencies (GSAs) can better manage their local water resources. SGMA requires GSAs to consider ISW in their groundwater sustainability plans (GSPs), and this dataset can help GSAs better understand ISW in their region. Using data from 2011-2018, the ISW dataset represents the likely connection between surface water and groundwater for rivers and streams in California’s Central Valley. It includes information on the mean, maximum, and minimum depth to groundwater for each stream segment over the years with available data, as well as the likely presence of ISW based on the minimum depth to groundwater. The Nature Conservancy developed this database, with guidance and input from expert academics, consultants, and state agencies.

We developed this dataset using groundwater elevation data available online from the California Department of Water Resources (DWR). DWR only provides this data for the Central Valley. For GSAs outside of the valley, who have groundwater well measurements, we recommend following our methods to determine likely ISW in your region. The Nature Conservancy’s ISW dataset should be used as a first step in reviewing ISW and should be supplemented with local or more recent groundwater depth data.

Download the methods.