Basin Conditions

View the Groundwater Conditions Fact Sheet for an in-depth look at groundwater conditions in the basin.

Over the past several decades, the Sonoma Valley has experienced significant population growth and land use changes, including increases in irrigated agriculture, primarily vineyards. These changes have increased demands on water and groundwater resources, and groundwater levels are declining in portions of the valley. 

Groundwater Levels

Groundwater levels within Sonoma Valley’s shallow aquifers are generally steady, although localized declining trends have been observed in the El Verano/Fowler Creek area. Deep zone aquifers have also declined over the past decade, and do not recover during wet years according to monitoring wells and stream level observations. These chronic declines indicate that groundwater withdrawals are occurring at a higher rate than recharge or replenishment.


Groundwater Quality

Groundwater quality is generally good within Sonoma Valley. However, wells in southern Sonoma Valley (generally south of Highway 116) have been affected by brackish or salty groundwater. If groundwater levels continue to drop in the north, brackish water could be drawn further north, potentially affecting more northern wells and rendering groundwater unusable.


Groundwater Sources and Usage

Covering 166 square miles, the Sonoma Valley groundwater basin contains approximately 2,000 domestic, agricultural, and public supply wells. It is estimated that 3.42 billion gallons of groundwater was used in the Sonoma Valley in 2012, representing nearly 60% of the valley’s water supply. The remainder comes from the Russian River, other local surface water, and recycled water.


Maps and visual displays of groundwater conditions are in process. Check this page regularly for more information.