Saltwater Intrusion and Drought Salinity Barriers
A photo of the West False River emergency drought barrier.
The Sacramento-San Joaquin Delta (Delta) is influenced by tides from the San Francisco Bay with flood tides pushing ocean water upstream. However, if saltwater were to intrude too far inland and enter the central Delta, fresh water supplies would be compromised. This would impact Delta agriculture, local municipal supplies, and the natural environment. Additionally, California’s primary water delivery system, which supplies water to 27 million Californians and supports the world’s fifth largest economy, would be threatened.
Generally, flows from the Sacramento and San Joaquin Rivers keep tidal saltwater out of the central Delta. However, during periods of extreme drought, the natural upstream flows combined with water releases from upstream reservoirs provides inadequate flows necessary to prevent salty ocean water from moving into the central Delta and through the Delta. The prevention of saltwater intrusion requires intervention and presents a tough water management challenge. Data from past installations have demonstrated that drought salinity barriers significantly minimize saltwater intrusion.
A drought salinity barrier is a physical obstacle which could be constructed in one or more strategic Delta channels to:
- Effectively prevent tidal saltwater intrusion into the Delta
- Protect water quality and prevent contamination of Delta water, including water for Delta agriculture and municipal supplies
- Reduce the amount of water released from upstream reservoirs during a drought which preserves stored water for future needs.
Figure 1 - This map shows the locations of the West False River Drought Salinity Barrier near the mouth of the West False River.
In an effort to better prepare for future drought conditions in the face of climate change, DWR has released a draft Environmental Impact Report (EIR) analyzing potential construction effects of future drought salinity barrier installations on the West False River in the Sacramento-San Joaquin Delta.
The draft EIR looks at the environmental impacts of installing a drought salinity barrier if needed across West False River in the Delta twice within a 10-year timeframe. The barrier, which would remain in place for up to 20 months, would help reduce saltwater intrusion into the interior Delta providing the State with greater flexibility to respond to future droughts, which are growing more frequent and extreme due to climate change.
As California prepares for the possibility of a fourth dry year, the West False River salinity drought barrier is one important action available to DWR to help protect the beneficial uses of Delta water.
The release of the draft EIR kicked off a 45-day comment period that ended August 22, 2022. DWR hosted a virtual public hearing on the draft EIR on July 27, 2022, to provide information and receive verbal comments.