RESTON, VA — A new, three-dimensional water-modeling tool has already led to some interesting observations about California’s Central Valley, the focus lately of sharp debate about water availability and use.

The tool is designed to provide a detailed picture of how water flows below ground and how it relates to surface water in rivers and canals, and it has been used to model groundwater levels in the Central Valley, the US Geological Survey (USGS) announced July 8.

USGS scientists found that groundwater levels in the southern Tulare Basin portion of the San Joaquin Valley — the southern part of the 400-mile-long Central Valley — are declining as more water is pumped out than is recharged naturally. But the southern Central Valley also shows the most promise for large-scale artificial groundwater recharge, particularly along the eastern side, according to research led by USGS hydrologist Claudia Faunt.   

In contrast, groundwater levels in the Sacramento Valley (the northern part of the Central Valley) and the northern portion of the San Joaquin Valley are generally stable, the USGS reported.

The tool, the Central Valley Hydrologic Model, is available for use by water managers and other agencies. The model was designed to help resource agencies assess, understand and address the many issues affecting the joint use of surface and groundwater supplies — known as “conjunctive use” — in the Central Valley.

According to Faunt, “The detail and breadth of this hydrologic model will make it invaluable to water resource managers faced with increasing water management challenges and constraints. In the future, the Central Valley Hydrologic Model could be used to evaluate regional issues such as exportation of water from the Sacramento Valley to Southern California or the upcoming restoration of salmon habitat in the San Joaquin River.”

A professional paper detailing Faunt’s research, “Groundwater Availability of the Central Valley Aquifer, California,” is available online.

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