Thoughts on DWR’s Delta Conveyance Webinar on Fisheries

The single tunnel project was supposed to be redesigned to limit impacts on Delta legacy communities and fish.  But many of the bad design decisions from the previous project have been kept. The most glaring examples are the enormous, 3,000 cfs intakes, which were carried over from the twin tunnels project. Dave Vogel wrote about the twin tunnels project intakes:

Three extremely long flat-plate fish screens would be positioned in front of each huge water diversion intake (Figure 1). The size of these screen structures will be massive, greatly exceeding the size of existing fish protective facilities in California. The combined length of the three screens will extend nearly 3/4th of a mile! The concept has never been tested elsewhere, possess numerous harmful obstacles for fish, and will likely kill large numbers of salmon. There is a high probability the structures will be catastrophic for salmon and severely undermine progress for salmon restoration in upstream areas.

The only major change from the twin tunnels project is that there are now only two extremely long intakes, which will still likely kill large numbers of salmon.  And also be disastrous for the town of Hood and the North Delta wine tourism business. It also appears that DWR still hasn’t done all of the required field studies to test the design.

In 2011, the BDCP Fish Facilities Technical Team recommended the following studies be done (and see table below)

Near-term studies and research are needed to reduce key uncertainties prior to design and construction of water diversions and fish screens. The scale of this project is uniquely large, both in terms of the total pumping rate and the physical dimensions of diversions and fish screens at each site. The many uncertainties that exist with a project of this size require physical modeling, numerical modeling, and field studies to direct design decisions.

Specific hydraulic and aquatic biological information about the site locations must be collected before design. Some information about screen performance and fish behavior is available at similar sites in the region such as Freeport, Reclamation District 108, Sutter Mutual Water Company, Patterson Irrigation District, and Glenn Colusa Irrigation District, but none of those facilities present the same environmental conditions that will exist at any of the five proposed facilities; therefore additional research is necessary. Baseline studies are required in order to analyze the impacts of the diversions on fish populations.

           (emphasis added.)

It appears that the Delta Conveyance Design and Construction Authority has not completed the site location lab study required to validate that the 3,000 cfs intake concept. Instead, they just carried over the untested design specification from the previous project.  They are proposing to use cylindrical screens rather than flat plate screens, a minor change that will in no way adequately mitigate the disastrous effects of the enormous 3,000 cfs intakes on salmon.

When I asked in the webinar about putting a flow sensor at Hood to gather river flow and velocity data, Carrie Buckman stated that DWR would consider doing that after the intakes are constructed.

Here is the full table of studies that were recommended in 2011 by the Fish Facilities Technical Team.FFTT Recommendations


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