Construction of a temporary emergency drought barrier at West False River in the Sacramento-San Joaquin Delta is nearing completion about two weeks sooner than anticipated, according to the Department of Water Resources (DWR).
The barrier now spans the approximately 750-foot-wide river between Jersey and Bradford islands and blocks salt water that tidal action attempts to push eastward from San Francisco Bay into Franks Tract. The trapezoidal barrier is about 120 feet wide at its base and 12 feet wide at its top above the waterline. About 150,000 tons of rocks have been dropped from barges with hinged bottoms or lifted from barges and dropped by crane into the river’s channel to create the barrier.
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 emergency barrier also will help mitigate a worst-case circumstance in which upstream reservoirs lack sufficient water to meet the minimum outflow requirements to limit Delta salinity intrusion.
Some 25 million people rely on the Delta-based federal and state water projects for at least some of their supplies, including residents of the Delta and Contra Costa, Alameda and Santa Clara counties.
Adding to water managers’ concerns during the drought is California’s record-low snowpack, which will contribute little runoff into reservoirs as it melts. Storage in all of California’s major reservoirs currently is far below historical averages for late May. Shasta Lake, the state’s largest, is at 62 percent of that average, Lake Oroville is at 53 percent and New Melones now holds 30 percent of its late May average.
Boat passage on West False River is now blocked by the barrier, which will be removed by mid-November to avoid the traditional flood season and potential harm to migratory fish. Removal is expected to take 45 to 60 days.
Warning signs, lights and buoys alert boaters of the barrier’s presence. DWR notified marinas and individuals in the Delta about these restrictions several weeks before construction began. Alternative routes between the San Joaquin River and interior Delta, including Bethel Island marinas, are available
Design, installation, monitoring and mitigation are estimated to cost roughly $22 million; the cost for removal is estimated at $15 million. Costs are to be paid with a mix of funding from Proposition 50, a $3.4 billion water bond approved by voters in November 2002, and General Fund dollars.
Earlier Consideration of Emergency Barriers
The West False River site raises fewer concerns for threatened and endangered fish than other potential barrier sites considered by DWR. Last year, DWR studied the potential impacts of potential temporary barriers at three locations: Steamboat Slough, Sutter Slough and West False River. The analysis found anticipated impacts could be mitigated to a less-than-significant level. DWR received and reviewed considerable public comments on the Initial Study and Proposed Mitigated Negative Declaration, available here. DWR is not pursuing installation of temporary emergency barriers at Sutter Slough or Steamboat Slough in 2015.
The April 1, 2015 Executive Order by Governor Brown helped expedite installation of the West False River barrier in time to address emergency drought conditions this year. DWR last used emergency drought barriers to reduce salinity intrusion in 1976-77. DWR considered the installation of emergency drought barriers in 2014 but determined in late May of last year that they would not be needed, in part because February and March storms improved water supply conditions. Planning for future emergency drought barriers continued after last year’s decision, with a focus on West False River, Steamboat Slough and Sutter Slough.
Earlier this year, based on the input of Delta residents, the Department also considered the feasibility and effectiveness of barriers on Miner Slough in the western Delta and on Steamboat Slough downstream of its confluence with Sutter Slough – in lieu of the original Sutter Slough and Steamboat Slough locations.
Emergency drought barriers on Miner and Steamboat sloughs were eliminated from consideration because of U.S. Fish and Wildlife Service concerns about potential effects on threatened Delta smelt.
Current Drought Emergency
The three-year period from 2012 through 2014 was the driest three-year period on record in California, and 2015 opened with the driest January in the state’s recorded history. The Sierra Nevada snowpack typically peaks by April 1; this year, the snowpack was measured at five percent of historic average on April 1, the lowest measurement in recorded history.
Governor Brown declared a drought State of Emergency on January 17, 2014 and directed state officials to take all necessary actions to prepare for water shortages. The State Water Resources Control Board on March 17, 2015 announced new restrictions on water use, including limiting outdoor watering to two days per week and prohibiting lawn watering during rainfall and during the following two days.
In April, Governor Brown directed the State Water Board to implement mandatory water reductions in cities and towns across California to reduce water usage by 25 percent. On May 5, the State Water Board established water conservation standards for communities throughout the state, ranging from a low of 4 percent to 36 percent as compared with a community’s 2013 water use and depending on per capita water use in each community.