Saltwater Intrusion and Drought Salinity Barriers
Generally, State and Federal water projects provide enough flow to keep saltwater out of the interior Delta. However, during periods of extreme drought, there may be too little water stored in upstream reservoirs to provide the flows necessary to prevent ocean water from moving upstream through the Delta. This scenario presents a tough water management challenge, requiring certain measures like drought salinity barriers to minimize saltwater intrusion.
Drought salinity barriers are a physical obstacle constructed in strategic Delta channels to:
- Help prevent saltwater intrusion
- Protect water quality and prevent contamination of water supplies for Delta agriculture and municipal supplies
- Reduce the amount of water released from reservoirs upstream to keep the ocean water out of the interior Delta
This map shows the locations of the current West False River drought salinity barrier near the mouth of the West False River and the locations of the potential North Delta drought salinity barriers at Miner and Steamboat Sloughs.
In response to worsening drought conditions in California, DWR constructed a temporary Emergency Drought Salinity Barrier across the West False River in the Sacramento-San Joaquin Delta in June 2021.
The approximately 800-foot-wide temporary barrier, consisting of nearly 90,000 cubic yards of rock, was located near the mouth of the West False River where it flows into the San Joaquin River. The barrier helped to prevent incoming salty tides from intruding into the interior Delta at this location.
At the end of the 2021 water year on September 30, the continuing dry conditions and low storage levels provided clear evidence of the dire hydrologic conditions across the State. As a result, DWR updated the Emergency Drought Salinity Barrier deployment plan to accommodate a delay in the barrier’s removal from fall 2021 until a future date when it is determined that the barrier is no longer needed, with full removal by November 30, 2022. Keeping the barrier in place longer has provided continued protection of fresh water supplies in the central and south Delta.
The barrier, which blocked watercraft passage on West False River, was marked by warning signs, lights, and buoys. Alternative routes between the San Joaquin River and interior Delta were available. To facilitate fish and boat passage from January to March 2022, DWR installed a temporary 400-foot-wide, 12-foot-deep notch in the barrier.
DWR’s existing environmental monitoring program continues to assess the physical and biological effects of the barrier and its impact on the Delta.
In response to Governor Newsom’s 2021 Emergency Drought Proclamation, DWR has begun planning for the potential North Delta Drought Salinity Barriers Project. If drought conditions continue to worsen into the 2022 water year and beyond, the proposed project would be implemented as early as June 2023 to provide additional protection from saltwater intrusion. The proposed project consists of installing temporary rock barriers on Miner Slough and Steamboat Slough in the north Delta.
The objectives of the proposed project are to further minimize the impacts of salinity intrusion on Delta water quality during severe and persistent drought conditions. The project would include installation of temporary rock barriers to conserve flow in the Sacramento River by reducing salinity intrusion.
The barriers are intended to specifically benefit:
- Communities and farmers in and adjacent to the Delta who rely exclusively on this source for drinkable water and irrigation.
- Upstream resources and communities, because once installed, the barriers would reduce demand on reservoir releases to maintain salinity levels in the Delta, leaving more water upstream for critical fishery and community needs.
- The State Water Project and Central Valley Project operators, as they attempt to maintain access to water supplies for human health and safety.
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.
- NOP Environmental Impact Report for West False River Drought Salinity Barrier Project
- West False River Drought Salinity Barrier Project CEQA EIR Public Meeting Presentation July 27, 2022
- West False River Drought Salinity Barrier Project CEQA EIR Public Scoping Meeting Presentation March 9, 2022
- West False River Drought Salinity Barrier Project Draft Environmental Impact Report July 2022