Baykeeper Update

Delta Water Tunnels Would Harm the Bay

The 35-mile tunnels proposed to carry freshwater from the northern end of the Sacramento-San Joaquin Delta to pumps on the southern end would harm San Francisco Bay. Baykeeper recently took action against the controversial $25-billion project by submitting comments opposing the Delta tunnels in the public review process for the proposal, which is officially known as the Bay Conservation Development Plan (BCDP).

The Sacramento-San Joaquin Delta supplies freshwater to cities and farms across California. However, demand far outstrips the available amount of water. The Delta is a fragile and overtaxed ecosystem that is already on the verge of collapse because unsustainable amounts of freshwater are being removed. The health of the Delta directly impacts the health of San Francisco Bay: it provides a vital source of freshwater, as well as carrying pollution from upstream sources into the Bay.

Dozens of environmental groups oppose the Delta tunnels because of the project’s potential to harm to the health of the estuary. Baykeeper agrees with the central concern that the tunnels will remove more freshwater from the northern Delta, causing it to become saltier and warmer. This will make it impossible for endangered Chinook salmon and other migrating fish species to survive in the northern Delta, and ultimately they and other species of fish would vanish from the Delta and San Francisco Bay.

Tunnel supporters claim that routing more freshwater through the tunnels to the southern Delta will reduce the high number of fish that are currently killed by the existing southern Delta pumps. However, removing as-yet-undetermined amounts of freshwater from the Delta could cause as much or more harm to fish than that caused by current pumping practices.

Proponents of the tunnels also point to the project’s restoring tidal marshes in the Delta and on the banks of some sections of the Sacramento River, claiming that it will make up for the tunnels robbing the Delta of freshwater. However, according to the best available science, the Delta and its wildlife will continue to deteriorate if California water agencies remove more freshwater. To save the Delta ecosystem, both habitat restoration and increased flows of freshwater are needed.

Removing more freshwater from the Delta is also likely to harm San Francisco Bay, yet the plan for the tunnels does not address environmental impacts to the Bay. In our comments on the tunnel plan, Baykeeper Staff Scientist Ian Wren pointed out how diverting more water from the northern Delta threatens the sustainability of the Bay’s ecosystem and wildlife.  

First, if the tunnels are built and the water diverted, less sand and other sediments will wash into the Bay from upstream. Sediments from the Delta help replenish Bay wetlands. By reducing sediment washing in from the Delta, ongoing efforts to restore wetlands around the Bay will be more difficult, and existing Bay wetlands will be less likely to survive as sea levels rise.

Second, water diversions could also change the ecosystem in northern areas of the Bay, including San Pablo and Suisun Bays. These waters are home to many species of fish that need a combination of fresh and salt water to thrive. Taking too much freshwater out of the mix will change the habitat and make it harder for these species to survive.

A third problem is that the tunnels are likely to increase the Bay’s levels of a toxic pollutant, selenium. Excess selenium can cause gross deformities in birds and fish, and poses similar dangers to humans who eat selenium-contaminated seafood. Selenium washes into the Bay from the San Joaquin River, one of the two major Delta tributaries. The tunnels will divert water from the other tributary, the Sacramento River, which has little selenium. That means a greater proportion of the freshwater that reaches the Bay will come from the San Joaquin, with high levels of selenium, and pose a serious risk to wildlife and human health. 

Baykeeper has a long history of taking action to protect the Delta, and we will continue to oppose the construction of costly, environmentally destructive tunnels designed to divert more freshwater out of the Delta. Instead, California needs to increase the amount of freshwater that flows into the Delta and the Bay, in order to restore and protect the Bay and Delta wildlife and ecosystem.

Photo by Daniel Parks (Flickr/CC)