The Sacramento-San Joaquin Delta is the heart of California’s water delivery system. With a long-term commitment to ecosystem restoration and scientific research, the Metropolitan Water District of Southern California invested in lands that are strategically located in the Delta. Metropolitan owns Bacon Island, Bouldin Island, Webb Tract and a majority of Holland Tract. Collectively, the lands offer multiple opportunities to support the state’s co-equal goals of a restored Delta and a reliable water supply for California.
Purchased in mid-2016, these islands and tracts are in the central Delta in important locations for both water supply and habitat.* Metropolitan’s water supplies through the State Water Project pass by four of the parcels. Bouldin Island and Webb Tract are in the migration pathways of important fish species such as salmon and delta smelt.
*Part of Metropolitan’s 2016 purchase was the western third of Chipps Island. In 2019, the Metropolitan board approved the sale of this property to the Department of Water Resources, which owned the rest of the island, to support a streamlined, maximized restoration process.
Some areas of the islands may provide the right conditions to develop food production (zooplankton) for fish. Restoring some areas with native tule vegetation would both rebuild peat soils to increase land elevation and reduce carbon emissions and protect the quality of drinking water sources. Conversion of some lands to non-tidal wetlands, or preserving cultivated land with food for bird species could significantly improve waterfowl habitat along the Pacific Flyway and achieve possible mitigation requirements for critical species.
Metropolitan is engaged in strategic planning for the islands that is focused on three policy areas. Land use includes identifying habitat opportunities, sustainable agriculture and ecosystem health and restoration. Science and research involves climate change risks, managing peat soils to reduce carbon emissions and increase carbon sequestration, and improve water quality and supply reliability. Levee reliability includes strengthening levees along the freshwater pathway, ensuring comprehensive emergency response, and reducing risk of levee failure during high river events. Metropolitan is working with state and federal agencies, technical experts, academia and environmental organizations.
This pilot project on Bouldin Island is studying floating peat wetlands, which historically existed in the Delta. If the floating peat mats can be re-established, it could reduce the time it takes to create a productive ecosystem in a subsided Delta and reduce the risk of levee failures. The project is a partnership between Metropolitan, the California Department of Water Resources, the UC Davis Center for Watershed Sciences and other entities.
California’s Delta water system relies on about 1,100 miles of levees that protect farms, cities, and people. For Delta islands, the levees surround subsided land that is below sea-level. These levees are vulnerable to earthquakes, floods and rising sea levels under climate change. When they fail, water rushes in, pulling in salt water from the bay and impacting water quality before it can be delivered to Southern California, the Bay Area and the Central Valley.
The $14.5 million Bacon Island Rehabilitation Project strengthened 4.7 miles of the island’s west-side levee. The project enhances the water conveyance pathway in the central Delta corridor and reduces the risk of a levee failure that would potentially impact water quality in the Delta and for the State Water Project and Central Valley Project. This project was completed with a grant from DWR and through the collaboration of urban water agencies: Alameda County Water District, Contra Costa Water District, East Bay Municipal Utility District, San Francisco Public Utilities Commission, Santa Clara Valley Water District, Zone 7 Water Agency and Metropolitan.
The existing approach to levee maintenance anticipates needs over a five-year cycle. This pilot project on Bouldin Island is evaluating the levees with a broad suite of technologies on a real-time basis to identify levee locations with critical needs, some of which may not be visible.
The program will allow for advanced planning to address levee maintenance and repair needs, and could be applied at other Metropolitan islands and DWR sponsored levee programs.
Photo courtesy of Department of Water Resources
Were Delta levees to fail due to an earthquake or other natural event, an “emergency freshwater pathway” would have to be constructed for fresh water supplies to move north-to-south through the Delta to the existing SWP and CVP pumping facilities.
DWR has stockpiled several hundred thousand tons of materials and equipment that can be quickly deployed in an emergency situation in the Delta. Materials include quarry rock, sand and soil that could be used for flood protection, channel closure and breach repairs.
Webb and Holland tracts are two of the eight priority islands identified by the state for special protection because of their location in the western Delta and potential to counteract salt water intrusion. Metropolitan is working with DWR, U.S. Army Corps of Engineers, and local reclamation districts on emergency preparations and seismic analyses, and is ready to assist federal and state agencies with emergency response.
This project was completed with a grant from DWR and through the collaboration of urban water agencies: Alameda County Water District, Contra Costa Water District, East Bay Municipal Utility District, San Francisco Public Utilities Commission, Santa Clara Valley Water District, Zone 7 Water Agency, Metropolitan, and local entities Reclamation District #2028 and PG&E.”
The Sacramento-San Joaquin Delta is important to the state’s economy, water supply, and quality of life for millions of Californians.
Water that flows through the Delta watershed serves nearly 30 million people throughout California, and accounts for approximately 30 percent of Southern California’s water supply. It is home to a valuable, diverse ecosystem and legacy communities that have been around since the 1800s.
However, it faces challenges – including a declining ecosystem, sea-level rise, risk of earthquakes and subsidence of Delta islands. Advances in science and technology are improving understanding of these challenges, and many innovative and science-based projects are underway to boost endangered fish populations.
The Metropolitan Water District of Southern California