The California drought is so severe there isn’t enough fresh water flowing into the Sacramento Delta to prevent saline water intruding from San Francisco Bay. Thus, a rock barrier has been installed in a crucial area to prevent this. Fresh water from the Delta is pumped southward to the Central Valley and southern California and used by big agriculture and millions of people. It would be catastrophic if the water became saline.
Typically when saltwater threatens to encroach deeper into the Delta, water project operators repel it either by slowing the pumping of water from the Delta or increasing the amount of water flowing into the Delta from upstream reservoirs. In this fourth year of drought, Delta pumping by the state and federal water projects is already negligible, and it takes three to five days for fresh water released from Lake Oroville or Shasta Lake to reach the Delta.
The emergency barrier is an additional tool to help limit salinity intrusion should high winds or another unexpected event push salt farther east than expected this summer.
The barrier will be removed by mid-November, when the rains usually start. This year, with a powerful El Nino building, the rains could be substantial.