In a recent study, scientists found that a previously unmeasured source – water percolating through soil and fractured rock below California’s Sierra Nevada mountains – delivers an average of 4 million acre feet (5 cubic kilometers) of water to the state’s Central Valley each year. This underground source accounts for about 10% of all the water that enters this highly productive farmland each year from every source (including river inflows and precipitation).
As water grows more scarce in the Central Valley due to climate change and human use, a more detailed understanding of the natural movement of groundwater offers a chance to better protect the remaining resources.