Delta Corridors Plan – Improvements in Delta Channel Flows, Salinity and Fish Habitats

Ten Good Reasons to Reconsider the Delta Corridors Plan in 2020

1. All of the San Joaquin River water, salt, phytoplankton and migrating juvenile fish would bypass the CVP and SWP export pumps and would instead move down Old River to Franks Tract and to the San Francisco Estuary. This would eliminate the recycle of SJR salt back to the Delta Mendota Canal and would reduce the average salinity of the exports by more than 25%. This would eliminate any salvage or loss of SJR migrating juvenile fish (e.g., Chinook, steelhead, splittail). The high chlorophyll concentrations in the SJR during the summer months would no longer be exported but would supplement the food-web in Old River, Franks Tract and in Suisun Bay.

2. Migrating juvenile Sacramento River fish (e.g., Chinook, steelhead, American shad, splittail) would be protected by fish screen facilities at the Delta Cross Channel and at Georgiana Slough near Walnut Grove. The DCC would be divided with a wall and the north gate would be opened to provide a connection to the Mokelumne River and the tidal habitat of Snodgrass Slough. This would increase the survival of juvenile steelhead and Chinook and allow increased rearing in the Snodgrass Slough channels. The south gate would be automatically operated to regulate diversions to Snodgrass Slough and the NF Mokelumne River with a maximum of 5,000 cfs with an approach velocity of 0.33 ft/sec during flood-tides (existing peak flows are 10,000 cfs). A large flat-plate wedge-wire fish screen would be constructed along the Sacramento River levee extending 1,000 feet downstream to the Walnut Grove dock. The Georgiana Slough fish screens would extend 1,000 feet upstream and downstream to provide a maximum diversion of 10,000 cfs. Screened diversions from DCC and Georgiana Slough would flow south in the San Joaquin River and Middle River channels to provide all of the CVP and SWP exports.

3. The CVP and SWP exports would no longer need to be reduced in April and May to improve the survival of migrating SJR juvenile Chinook and steelhead. Export reductions to protect delta smelt and longfin smelt spawning and rearing in the SJR channels upstream of Antioch would no longer be necessary because there would be no entrainment of adult nor juvenile fish from the confluence or lower San Joaquin River or Franks Tract or Old River channels. Exports could be increased to match the fish-free diversions from the DCC and Georgiana Slough. New rules for operating the CVP and SWP exports could be developed to reflect these changes in entrainment risk.

4. Separating the SJR-estuary corridor along Old River through Franks Tract to the SJR confluence near Antioch from export pumping will prevent entrainment of all migrating SJR fish (Chinook, steelhead, splittail) and will prevent the entrainment of estuarine spawning and rearing fish (e.g., delta smelt, longfin smelt). The SJR-estuary corridor will increase the potential spawning and rearing habitat area by about 15,000 acres (30% of the area upstream of Chipps Island). The survival of migrating SJR juvenile fish should be improved because the migration corridor will be faster (less volume in Old River than in the SJR) and the banks of Old River are more vegetated (e.g., tules) and should provide more rearing habitat and protection from predators.

5. The Delta channels between Old River and Middle River would be blocked with walls to separate the water-supply corridor in Middle River from the SJR-estuary corridor in Old River. The 75-miles of levees along these channels from the tip of Bradford Island in the west to the tip of Victoria Island in the south would be strengthened and these levees would be the first to be re-built following a catastrophic failure (e.g., earthquake) to re-establish (separate) the water supply corridor between the DCC and Georgiana Slough diversions and the CVP and SWP exports. Full exports could be resumed as soon as these levees between Old River and Middle River were repaired.

6. Portions of Middle River and Victoria Canal channels would be dredged to allow full permitted exports (12,000 cfs) to flow down Middle River and Victoria Canal to the CVP and SWP pumps without reducing the water elevations to less than the minimum needed at the export pumps (to prevent cavitation). Dredging of about 10 million cubic yards along Middle River and Victoria Canal will provide material that is needed within the Delta to reinforce berms on the landward side of the levees along Middle River and Old River. Full capacity exports of 15,000 cfs would be possible during high SJR inflows when the DC Plan flood-gates at the head of Old River, at the north end and south end of West Canal and at the mouth of Old River would be opened.

7. The effectiveness of the CVP and SWP fish salvage facilities would be improved because the majority of fish and vegetative debris (i.e., water hyacinth matts) would be separated from the salvage facilities in the Old River channel. The reduced debris-load may allow the primary louvers at the CVP fish facility to be replaced with travelling fish screens. A 2.25-mile long rock wall constructed along the south shore of Clifton Court Forebay would create a 200-feet wide channel that would reduce the predation losses in CCF. Water and fish entering the CCF gates would flow directly to the SWP fish facility with a travel time of 2 hours rather than 2 days (residence time in CCF) for 5,000 cfs of SWP pumping.

8. All of the treated wastewater discharges to the SJR and in the southern Delta (e.g., Lathrop, Manteca, Stockton, City of Tracy, Mountain House, Discovery Bay) would be mixed and transported to the estuary in the Old River corridor and would no longer be exported in the CVP and SWP and CCWD water supplies. The drinking water quality would be improved by eliminating the treated wastewater and the agricultural chemicals and contaminants from the CVP and SWP exports and from CCDW diversions.

9. The environmental impacts of the DC Plan have already been evaluated as Alternative 9 of the Bay-Delta Conservation Plan EIS/EIR. Additional documentation of the project-level impacts (and likely benefits) could be prepared by building on the existing analysis of the Delta environmental resources. Each of the DC Plan facilities and channel changes can be constructed without damaging any of the existing levees or removing any of the existing facilities in the Delta. The DC Plan facilities and channel changes could be constructed and operated for a trial period of 2-3 years to test and evaluate their effectiveness. The facilities could be modified or removed if the expected benefits were not observed or if unexpected negative consequences were identified.

10. The DC Plan facilities and channel modifications can likely be constructed within a 3-year period with a likely cost of less than $2 billion. This investment in the hub of California’s water supply system would have many long-term payback benefits. Water supply reliability from the Delta would be increased and fish habitat protections and migratory fish protections would be improved. The conflicts between our shared responsibilities for water supply and fish protection would be reduced. These are expectations that would likely be achieved with the DC Plan.