Delta could get saltier if tunnels are built
The two giant water diversion tunnels Gov. Jerry Brown proposes building in the Delta would be large enough to meet annual water needs for a city such as Newport Beach in a single day's gulp from the Sacramento River.
That gulp, however, would also prevent a lot of fresh water from flowing through the Sacramento-San Joaquin Delta. This would likely make water saltier for farms near Isleton and cities such as Antioch, which draws some of its drinking water from the Delta.
This marks just one of the complex trade-offs sprinkled through the Bay Delta Conservation Plan, the massive proposal to re-engineer California's primary water delivery system that includes the two tunnels.
The plan is intended to resolve decades of conflict between human demand for river water in counties south of the Delta, which are eager to secure water supplies in the face of earthquakes and climate change, and the harmful consequences for the estuary's imperiled wildlife, including native fish such as chinook salmon and Delta smelt.
Whether the project ultimately benefits these species, and the people of Northern California, depends largely on how the tunnels change various aspects of water flow in the Delta – how much water is flowing through and from what mix of sources.
The engineering described in the Bay Delta plan would result in the biggest water flow changes in the Delta in 50 years, and they are the most complicated aspect of the project. Even proponents, after seven years of study, can't explain all the potential consequences.
A draft environmental impact study is expected to be released for public review by Oct. 1, and a decision is planned by April 2014. In the meantime, the California Department of Water Resources has released thousands of pages of planning documents, including an "interim" draft of a required environmental impact study.
These documents describe many of the likely water flow changes. They also illuminate a lot of uncertainties.
For example, officials have no specific solution to prevent farms and cities in the Delta from losing access to fresh water if the tunnels make the estuary saltier. They merely propose to consult with the affected entities to provide compensation or alternate water supplies after the fact.
Another example: Diverting the Sacramento River means the San Joaquin River would compose a larger share of the water in the estuary. The San Joaquin is poorer quality water, laden with salt, pesticides and selenium, a naturally occurring mineral that can deform wildlife in excessive concentrations.
Some of the effects of these water quality changes are deemed "unquantifiable" in the planning documents due to scientific uncertainties. Officials intend to manage selenium, for example, by planting vegetation in restoration areas in hopes plants would absorb it.
The project would be approved as part of a habitat conservation plan, which would receive a 50-year-operating permit from state and federal wildlife agencies. By agreeing to sweeping habitat improvements, DWR would qualify for a permit that would exempt the agency and its contractors from routine water delivery cutbacks, which occur now under laws that protect endangered species such as Delta smelt and spring-run salmon.
The tunnel proposal has sharply divided the state's elected officials between north and south. Southern California politicians generally support the project because it would help secure water deliveries for their constituents.
North state officials generally oppose the project, saying it would harm water supplies in the Delta and their constituents who depend on those supplies for crop irrigation and drinking water. About a week ago, five members of Congress gathered on the Sacramento waterfront to condemn the plan.