The Twin-Tunnels Project: A Disaster for Salmon Part 4 of a Series

Ring the Dinner Bell!

Despite the extraordinary hazards facing salmon as described in the previous Parts 1, 2 and 3, the greatest source of mortality at the Twin Tunnels’ water intakes will very likely be caused by artificially-induced predation. This topic in the fourth part of this series is probably the most complex and, arguably, most controversial. Here is where all bets are off and we enter the realm of diverse scientific opinions among experienced fishery biologists.

The high level of concern about predation at proposed massive water intakes on the lower Sacramento River is not new. It boiled to the surface during planning for the infamous “Peripheral Canal” that was roundly rejected by California voters in 1982. Based on an extensive literature review, veteran fishery biologists Odenweller and Brown1 (1982) summarized the need for minimizing predation associated with the proposed Peripheral Canal fish facilities:

“The literature offers some assistance for minimizing and discouraging predation at the intakes and fish facilities. Piers, pilings, other supportive structures, and corners or other irregularities in a channel are referred to as structural complexities. Such structures may cause uneven flows and can create shadows and turbulent conditions. A structurally complex environment should be avoided.”

Unfortunately for salmon, the planning documents for WaterFix reveal that such artificial structures for the Twin Tunnels’ intakes will provide a vast detrimentally complex environment favoring predatory fish habitats. The documents provide no credible details on how that crucial problem will be solved.

The 2017 National Marine Fisheries Service Biological Opinion (BiOp) for WaterFix states that 32 – 40 vertical pilings will be placed directly in front of each of the three water intakes (or more than 100 total pilings!). The alignment of the pilings will be positioned just off the face of the fish screens and parallel to the migration pathway for salmon, greatly adding to the formidable gauntlet of waiting predators. Furthermore, an enormously-long floating boom (also parallel to the screens) will be supported by the pilings, accumulating and exacerbating the structural complexity Odenweller and Brown (1982) warned against 35 years ago. Even the BiOp openly admits that “These structures create habitat that provides holding and cover for predators.” I have heard it said, “We learn from history that we do not learn from history.”2 And so it goes with the Twin-Tunnels Project.

Based on research I have conducted since 1981, salmon predators are highly opportunistic and quickly adapt to habitats where salmon can easily be preyed upon. Remember the giant “toothbrush” wiper blades mentioned in Part 2 of this series? Using a high-tech sonar camera, I have observed predators hiding behind such wiper blades, darting out and eating unsuspecting salmon that have no protective cover. This clear predation predicament will be greatly intensified due to the very low sweeping velocities at the proposed WaterFix fish screens (discussed in Part 1 of this series). Predatory fish (e.g., striped bass and pikeminnow) can easily swim back and forth in front of the screens with minimal expenditure of energy, gobbling up highly-vulnerable, fatigued salmon like popcorn.

Although problems facing salmon will be worse when the intakes are in operation, the in-river structures alone will remain a serious hazard for salmon even when no water is diverted. For example, if those facilities were in place during the recent four-year drought, little or no water would have been diverted into the Twin Tunnels. Nevertheless, the salmon would still have had to migrate past the non-operating intakes where predation would likely remain high. I have already observed large numbers of striped bass concentrated near an artificial structure just upstream of the proposed intakes locations (see: Striped Bass). The WaterFix structures will be permanent fixtures in the river, forever tipping the scales in favor of predatory fish habitats over salmon habitats.

Unfortunately for the salmon, there is not just one, but three intakes for WaterFix. In the worst-possible scenario for salmon, all three water intakes are to be located on the same side of the river and in relative close proximity. Water (and therefore fish) will be driven toward the east riverbank, particularly when all intakes are operating in unison. Up to 3,000 cfs will be removed from the river at each of the three intakes with many baby salmon undoubtedly drawn to the east riverbank. What this means is that the increasingly fatigued and exposed downstream-migrating juvenile salmon will become more and more consolidated along the east bank of the river as the fish traverse the long length of each individual screen structure and arrive (if the fish have not already perished) at the downstream end (Figure 1). This sequence of events will culminate in a very undesirable concentration of salmon, but a perfect environment for the predators as well. Predatory fish will unquestionably become accustomed to these ideal “feeding stations” at the lower end of each fish screen. These highly-adaptable predators simply have to wait for dinner to be delivered at the downstream end of the fish screens. The resultant impacts on juvenile salmon could well be catastrophic. WaterFix does not describe tangible solutions for how this grave predation dilemma can be avoided other than employing the use of “adaptive management” (discussed next in this series).

Figure 1. Conceptual plan-view schematic (not-to-scale) of the three proposed WaterFix intakes on the Sacramento River and the concentrating effect on downstream migrating salmon toward the east or left bank (facing downstream).


Odenweller, D.B. and R.L. Brown.  1982.  Delta fish facilities program report through June 30, 1982.  FF/BIO 4ATR/82-6.  IESP Technical Report 6.  December 1982.  90 p.

Next in the Series:  Adaptive Management – Salmon Salvation?

  1.  Ironically, Odenweller’s and Brown’s employers (California Department of Fish and Game and California Department of Water Resources, respectively) supported the Peripheral Canal.
  2.  Quote attributed to Georg Wilhelm Friedrich Hegel.

The Twin-Tunnels Project: A Disaster for Salmon Part 3 of a Series

The Myth of the Salmon “Motels”

As previously discussed in Parts 1 and 2 of this series, due to the poor intake locations of the Twin Tunnels, the unacceptably low sweeping flows past the intakes’ fish screens, and exceedingly and harmfully long exposure time of young salmon to the screens, the fish will encounter a formidable gauntlet while attempting to migrate to the ocean. The Twin-Tunnels project proponents begrudgingly realized that the daunting length of the three fish screens will likely result in salmon impingement and other problems. Their solution? Slap on yet another unproven measure to supposedly provide temporary “refuge” for the weakened fish traversing the long screens. As stated in the 2016 WaterFix Final EIR/EIS1:

“Because of the length of the screens and extended fish exposure to their influence (screens and cleaners), fish refugia areas have been recommended to be incorporated into the screen design of the intakes (FFTT 2011). These areas would consist of small areas created within the columns between the fish screens that will provide small fish resting areas and protected cover from predators. Design concepts for fish refugia are still in their infancy and are usually site-specific, with designs recommended by the fish agencies (Svoboda 2013).”

Essentially, they have recommended embedding miniature, shallow cages (Figure 1) in concrete columns placed between the screens, trusting that as the salmon inevitably become exhausted and by some means avoid being squished by the screen wiper blades (referred to as “cleaners” in the statement above), the fish will somehow enter the small cages and avoid mortal injury.

Figure 1. Example of a so-called “refuge” for juvenile salmon envisioned for the Twin Tunnels’ intakes. This particular structure (dewatered during construction) was installed at a fish screen in Red Bluff, CA and, to this author’s knowledge, has never been tested. Photo is from Svoboda 2013.

Envision a weary human traveler driving from New York to L.A. Eventually, the traveler checks into a motel to rest and emerge the next morning with renewed energy to continue the arduous journey to his/her final destination. Such is the basic concept for salmon at the Twin Tunnels’ intakes. Essentially, the Twin Tunnels’ proponents have suggested providing “motels” in the WaterFix intakes to theoretically provide a respite for the fatigued salmon on their downstream voyage. To continue surviving this gauntlet, once the small fish supposedly enter a motel, the fish ultimately have to leave and continue along the screens until, in theory, another motel is fortuitously encountered. Of course and unfortunately, if salmon enter these motels, so can massive amounts of riverine debris; the resulting limited space, if any, will have to be shared. Many of these highly experimental motels are proposed for each of the three huge fish screens.

This salmon motel design has never been actually tested in a river and, based on my experience from countless hours of underwater observations of young salmon, has an extremely high probability of failure. I believe this was sort of a “Hail-Mary” attempt to avoid serious scrutiny of likely fish impingement and other problems. This concept was loosely founded on significant discoveries I made when conducting underwater inspections of a fish screen on the Sacramento River and found large numbers of young salmon residing in a very large, deep and wide chamber between trash racks and the screen (see: Salmon Discovery 1 and Salmon Discovery 2). Based on those findings, I offered a different promising bioengineering alternative for the proposed WaterFix fish screens; it was ignored.

Next in the Series: Ring the Dinner Bell!

  1. Environmental Impact Report/Environmental Impact Statement

The Twin-Tunnels Project: A Disaster for Salmon – Part 2 of a Series

Another biological problem with the Twin-Tunnels’ intakes:  Like gigantic vacuum cleaners, the flow pulled through the river intakes will likely suck baby salmon up against the fish screens (called “impingement”).  To minimize this problem, low through-screen water velocities (also called approach velocities) are necessary to hopefully prevent young salmon from encountering physical, injurious contact with fish screens.  The WaterFix proponents “promise” to keep those velocities low.  The biological problem with this premise is that juvenile salmon are weak swimmers on a sustained basis and cannot tolerate swimming against approach velocities through the screens for long periods.  When naturally migrating downstream, the small fish essentially “go with the flow” and do not aggressively fight against the current, except in unavoidable desperation (see: Struggling Salmon).  To avoid impingement, the salmon suddenly have to fight against the flow entering the WaterFix intakes.  The small salmon can only combat the currents for short periods until fatigue sets in and eventually succumb to the water flowing into the screens.

In the not-so-distant past, to minimize this fish impingement problem, a federal criterion mandated that young salmon should not be exposed to fish screens for more than 60 seconds, even with low approach velocities.  The biological concept is to move salmon very quickly past the screens before the fish surrender to the through-screen velocities, come into contact with the screens, and eventually die from abrasions and physical injury.  With large, long screens, this poses a very serious predicament.  In case of the Twin-Tunnels’ screens, it will not be possible to get the salmon away from the screens in less than a minute because of the large surface area and great length necessary to keep the through-screen velocities low while simultaneously maintaining high water diversion rates.  The salmon can only escape if swept by the long screens extremely fast.  In this regard, the Twin-Tunnels’ fish screens will perform miserably.  Because of the poor locations of the intakes discussed in the first of this series, salmon will be exposed to the proposed screens for long periods because of severely low sweeping flows.  Analyses conducted for the project revealed that young salmon could be exposed to each of the three individual WaterFix screens for an astounding one-hour period (not a typo) … not exactly the original 60 seconds criterion mentioned above.

Additionally, it will not be possible to maintain uniform through-screen velocities along the entire length for each of the three screens.  Therefore, WaterFix proposes to install “flow-control baffles” directly behind the screens.  These would typify tall vertical Venetian blinds (Figure 1).  The WaterFix idea is that if too much flow (and therefore unacceptably high through-screen water velocities) occurs in a particular area (“hot spots”), the baffles would be pinched down to restrict flow entering that particular area of the screens.  The problem, in reality, is this proposed engineering solution will be like chasing ghosts.  As river flows and diversions change dramatically, the through-screen velocities and complex secondary currents will also change significantly over the entire area of the fish screens.  Tweak the baffles upstream, then it’s time to adjust the baffles downstream, and so on.  Once done, everything changes hydraulically and you have to start all over again … a never-ending battle of futile attempts to achieve the fairytale of flow uniformity over the entire screen face under all river and water diversion conditions.  Whew!  I would not want to be the poor workers chasing back and forth over the combined ¾ of a mile of fish screens constantly tweaking baffles 24 hours a day, 7 days a week when water is being diverted into the Twin Tunnels.

Figure 1. Picture of flow-control baffles in the open position (foreground) and flat-plate screens in the background. Entire structure dewatered during construction. Picture by Dave Vogel.

Unlike agricultural diversions in upstream areas that primarily divert water during the spring, summer, and fall, the Twin-Tunnels’ intakes will be diverting water over the winter season under high-flow conditions.  Unfortunately, this will undoubtedly cause unavoidable massive debris loading on the screens.  In attempts to deal with the plugged screen openings caused by debris, enormous vertical “wiper blades” will be in continuous operation going back and forth against the screen surfaces.  Envision giant tooth brushes constantly scrubbing in a futile attempt to stop the persistent “plaque” build-up (Figure 2).  Some existing smaller flat-plate screens used in upstream areas (where debris loading is far less and sweeping flows are very high) have successfully employed such wiper blades, but those situations are far different than envisioned with the proposed Twin-Tunnels’ intakes during the winter.  The Twin-Tunnels’ unfortunate reality is that with the poor sweeping flows, it will be extremely difficult, if not impossible, to get rid of the debris.  And where will it go?  The detritus will merely drift downstream and continue to plug the next screen panel, then the next, etc., etc.  The increased debris loading during high river flows is likely to be enormous1, overwhelming the wiper blades … WaterFix has not adequately addressed this dilemma.  And … for those hapless, fatigued young salmon struggling against or impinged on the screens when the robotic wiper blades bear down on the fish under the cover of darkness and muddy water? … Squish.

Figure 2. Picture of a flat-plate screen wiper blade. Entire structure dewatered during construction. Picture by Dave Vogel.

Next in the series:  The myth of the Twin-Tunnels’ salmon “motels”.

  1.  E.g, see pages 133 – 134 “Working Conditions in the Field” in Lufkin (ed.) (1990)

The Twin-Tunnels Project: A Disaster for Salmon Part 1 of a Series

The proposed “Twin-Tunnels Project” (aka “WaterFix”) would divert enormous quantities of water1 from the Sacramento River to the south Delta for export into the San Joaquin River basin and southern California. If the project is built as presently planned, it will likely be a disaster for salmon for reasons described in this series. Water entering the two gargantuan tunnels would be pulled through three colossal water intakes2 directly on the banks of the Sacramento River, a short distance downstream from the City of Sacramento. Except when the Yolo Bypass is flooding, all four runs3 of Chinook salmon in the entire watershed would be forced to migrate past these enormous diversions. 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. This series provides some highlights into the scientific basis to support that premise.

Figure 1. Conceptual rendering of one of the three on-bank intake facilities on the Sacramento River for the Twin-Tunnels project (Figure 3-19a from the 2016 Final EIR/EIS).

Location, Location, Location

Just like the old adage with real estate, fish screens must be located in good locations. Based on my 35+ years experience in the evaluation and bio-engineering of fish screens, in terms of hydraulic, physical, and biological conditions for fish protection, the proposed water intakes for the Twin-Tunnels are sited in some of the worst locations. Over a period of years, the Twin-Tunnels proponents presented the state and federal fish agencies with multiple hypothetical intake locations. It is evident that the agency representatives had no choice but to play with the losing hand dealt to them and recommended only general criteria that were severely constrained by the intakes sites. All of the options put forth were crappy … really crappy… for fish protection. It is obvious to me that the sites ultimately designated for the Twin-Tunnels project were not chosen because those locations would provide good fish protection but, instead, viewed as more favorable (but still bad) among the worst locations made available.

Because of the bad locations, the Twin-Tunnels’ screens will not have good “sweeping” flows to get the salmon out of the danger zone at the screens. Modern-day fish screens possess several features to help overcome the sweeping flow predicament for the Twin-Tunnels project. Sweeping flow complications can be partially alleviated by locating the screens on the outside bends of the river channel. An existing example of large Sacramento River flat-plate screen location demonstrates how that measure has been successfully implemented (Figure 2).

Figure 2. Aerial photograph showing an existing Sacramento River flat-plate fish screen located on an outside river bend to maintain high sweeping velocities. Water velocities passing the screen typically range between 2 to 4 feet/second.

In sharp contrast to such a real-world example, the three WaterFix intakes would be positioned in only very slight (or “gentle”4) river bends or relatively straight sections of the river channel (e.g. Figure 3) and, in all cases, undesirable lower gradient reaches of the river. Additionally, the Twin-Tunnels diversion intakes will be located in areas subject to tidal influence, further exacerbating the problems of ensuring protective sweeping flows. When the tide comes in twice a day, sweeping flows are reduced to the detriment of salmon.

Figure 3. Aerial photograph showing the approximate location of the proposed WaterFix downstream-most intake (termed “North Delta Intake No. 5”).

In summary, the Twin-Tunnels’ diversion sites will not provide the near-screen sweeping velocities necessary to protect downstream-migrating salmon. The noteworthy point is that past experience has clearly demonstrated that maintaining high sweeping velocities in front of large riverine flat-plate fish screens requires at least one of following to take place:

  1. Alter river channel geometry and create channel constrictions to control the hydraulic conditions at the fish screens.
  2. Position the fish screens on the outside sharp (not “gentle”) bend of the river channel where high water velocities are naturally present (e.g., Figure 2).
  3. Angle the fish screen out into the river channel in a downstream direction or jut the entire structure out into the channel in deeper, swifter water to maintain sweeping flows.

Unfortunately, the Twin-Tunnels’ intakes do not possess any of those conditions — period. Even the recently-issued National Marine Fisheries Service’s Biological Opinion on the Twin-Tunnels Project admitted that there is “a high degree of uncertainty” if the fish screens can be built to meet fish protection criteria because of the immense nature of the proposed screens.

Next in the series: How to squish baby salmon on a fish screen.

  1. 9,000 cubic feet per second (cfs).
  2. 3,000 cfs each.
  3. Fall run, late-fall run, endangered winter-run, and threatened spring-run.
  4. Adjective used in the original Twin-Tunnels EIR/EIS documents

Restoring Side Channels in the Upper Sacramento River

In a prior blog entry on this site, the importance of restoring juvenile salmon rearing habitats in the upper main stem Sacramento River downstream of Keswick Dam was described:  The main river channel is actually a harsh environment for young salmon upon emergence from the river gravels after hatching.  The weak-swimming fry are immediately exposed to very high water velocities and most of the riverbed lacks structure to provide those fish with velocity and predator refugia.  One hypothesis, albeit very difficult to prove, is that insufficient rearing habitats in the upper river may be a significant limiting factor for the salmon runs, particularly for the endangered winter-run Chinook.

Although the notion of increasing the quantity and quality of rearing habitats in the main stem Sacramento River has been discussed for decades, meaningful on-the-ground restoration actions have been lacking.  That circumstance is changing.  A management action now being pursued is the restoration of side channels that have lost ecological functions for salmon rearing, primarily because of diminished or total lack of hydraulic connectivity with the main river channel.   Many of the historical side channels have become plugged, stagnant, and choked with overgrown vegetation; excellent frog habitat, but not for salmon.

A major endeavor to reopen some side channels, probably the most complex in modern times, was recently completed on the upper Sacramento River in Redding, California (Figure 1).  Termed the North Cypress Street Project, multiple agencies and stakeholders successfully planned, initiated, and completed this action in 2016.  Finishing touches on the project were completed just prior to the new year.  Funding was provided by the Central Valley Project Improvement Act Anadromous Fish Restoration Program.  According to the Western Shasta Resource Conservation District which provided oversight for the entire effort, restoration of these side channels will provide rearing habitats for winter-run and fall/late-fall-run Chinook (Figure 2) through the provision of optimal flows, refuge from predators, and increased food sources.  The habitats will be particularly important for winter-run Chinook because nearly the entire population now spawns upstream of the site.

Figure 1.  Location of the North Cypress Street side-channel project to restore juvenile salmon rearing habitats.  The Painter’s Riffle project is located just upstream of Cypress Street which was previously described in this blog:

Figure 1. Location of the North Cypress Street side-channel project to restore juvenile salmon rearing habitats. The Painter’s Riffle project is located just upstream of Cypress Street which was previously described in this blog:

Figure 2.  Rearing juvenile Chinook.  California Department of Fish and Wildlife photograph.

Figure 2. Rearing juvenile Chinook. California Department of Fish and Wildlife photograph.

The completed restoration provides up to 1.48 acres of new side-channel rearing habitats at the minimum Keswick Dam release of 3,250 cfs (Figure 3).  The restoration included installation of numerous large woody debris structures to increase the habitat complexity for young Chinook.  Video footage of the project by John Hannon is provided at:  Side Channel Projects

More such actions are planned for implementation on the upper Sacramento River in 2017 and years beyond.

Figure 3.  Post-construction schematic of the North Cypress side-channel project.  Restored side channels are depicted by blue lines (courtesy of the Western Shasta Resource Conservation District).  Sacramento River flow is from the upper right to the lower left in the photograph.

Figure 3. Post-construction schematic of the North Cypress side-channel project. Restored side channels are depicted by blue lines (courtesy of the Western Shasta Resource Conservation District). Sacramento River flow is from the upper right to the lower left in the photograph.