This is an analysis of the claimed benefits for fish in the BDCP Plus fact sheet, Current Conditions for Fish Compared with the Bay Delta Conservation Plan
BDCP Plus has two claimed benefits for salmon:
1. Juvenile salmon would have better access to food on the Yolo Bypass floodplain, grow larger, and survive better as they enter the ocean.
The decision to flood the Yolo Bypass is an operating decision by the Department of Water Resources, so it is not necessarily linked to construction of a new conveyance. The proposed BDCP restoration of habitat in the Yolo Bypass and Cache Slough could help salmon, if there was a significant increase in inundation of the floodplain. DWR has not proposed to increase bypass flows, but will wait for 12 inches of sea level rise to raise the level of the Sacramento River. This is forecast for mid-century under climate change models.
2. 95% of juvenile San Joaquin Chinook salmon and 60% of Sacramento River Chinook salmon do not survive the trip through the Delta.
As the February BDCP effects analysis makes clear, major diversions on the Sacramento River would cause signficant entrainment of migrating spring and fall run Chinook salmon. DWR’s consultant recommended minimum Sacramento River flows of 7,000 cfs in the fall when the commercially important fall run Chinook are migrating. This would result in significantly reduced exports, and has been opposed by the water agencies. The minimum fall flows in the Feburary BDCP effects analysis are 4,000 cfs.
Overall, BDCP benefits for Sacramento River Chinook salmon are unclear, and there is a significant risk to populations from increased entrainment of migrating spring and fall runs.
BDCP plus has three claimed benefits for Delta smelt and Longfin smelt:
1. Estuary habitat quality and quantity would increase due to improved outflow and habitat restoration
Suisun Bay is important feeding habitat for Delta smelt and Longfin smelt. Increased diversions since 2000 have increased salinity in the bay to the point that it is not usable in the summer by the pelagic fish, as well as creating an explosion in the population of the invasive clam, Corbula amurensis. Biologists have recommended reduced diversions and increased outflows in wet and above normal years. However, this was blocked as a result of a lawsuit by water agencies. New operating restrictions proposed as part of BDCP will also likely be subject to legal challenge.
Benefits of proposed BDCP habitat restoration in Suisun Bay are linked to reducing salinity so that the Bay is usable by pelagic fish.
2. Plankton accumulation would improve through increased residence time in the Central and South delta, potentially enhancing foodweb support for longfin smelt and Delta smelt.
Toxic algae blooms in the Delta first appeared in 2000. Research links the blooms to increased residence time in the Central and South Delta — low flows and higher water temperatures. Sampling has also shown that the phytoplankton in the South Delta is almost entirely toxic algae. This is likely linked to the high level of nitrates in the San Joaquin River in the summer. Increasing residence time without cleaning up the San Joaquin River will likely increase toxic algal blooms, and could result in eutrophication and fish kills.
Any benefits of BDCP habitat restoration in the South Delta would depend on sufficient flows, as well as reducing nitrates and selenium in the San Joaquin River. Currently there is no proposal to provide these flows, and reduction of nitrates has been delayed for over a decade.
3. New intakes in the North Delta would feature state-of-the-art fish screens.
BDCP’s promise to provide state of the art fish screens is not new. The 2000 CALFED Record of Decision committed to putting fish screens on the existing pumps in the South Delta. The water agencies decided not to fund the project. Provision of adequate funding for BDCP mitigation commitments will be important in ensuring that mitigation commitments are met.
Overall the benefits of BDCP for Delta smelt and Longfin smelt are unclear, and there are significant risks from potential degradation of water quality in the Delta.
The most significant potential benefit for the Peripheral tunnel proposed as part of BDCP is in reducing reverse flows in the Central and South Delta. However, any reduction in reverse flows is strongly tied to the level of pumping. Increased water exports could actually increase reverse flows over existing conditions in some months.
