Category Archives: Bay-Delta

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

Posted on by

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

Posted on by

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 ↩

Enhancing Coleman Hatchery Salmon Contribution

Posted on by

In a recent post I discussed ways to improve hatchery salmon smolt survival to increase coastal and river salmon populations devastated by recent droughts. This post is a follow-up addressing how to enhance the Coleman (Battle Creek) Hatchery1 contribution. Coleman produces nearly half of the Central Valley’s 30 million hatchery-produced salmon smolts. Three state hatcheries in the Valley (Feather, American, and Mokelumne) produce most of the other smolts. Survival of Coleman hatchery smolts released to the Sacramento River is markedly lower in dry years.2 Trucking smolts from the hatchery to the Bay increases survival and catch in fisheries, but at a cost of increased straying and low return rates of adults to the hatchery.

Of all these hatcheries, Coleman has the toughest challenge, because it is nearly 300 miles from the Golden Gate. While trucking smolts to the San Francisco Bay improves smolt survival and adult salmon population numbers available to fisheries, trucking from Coleman leads to low hatchery-return rates and excessive straying to other Valley rivers. Only about 50-100 adults per million smolts trucked to the Bay find their back to Coleman. In contrast, for each million smolts released at the hatchery, 400-500 return to Coleman to contribute eggs for the next generation.

One measure to increase smolt survival-contribution I suggested in past posts is barging smolts to the Golden Gate. Unlike trucking, barging allows some imprinting by smolts for their eventual return route back to the hatchery. Barging requires a medium to large sized vessel, which would still necessitate nearly 200 miles of trucking to barge-accessible locations on the lower Sacramento River. Barging may reduce straying while providing enhanced smolt survival to the Bay, although past trucking and release at Knights Landing in the lower river only marginally lowered the straying rate compared to Bay releases. A balance between overall survival and contribution to the fishery and returns to the hatchery is the challenge for fisheries managers. Barging from Knights Landing or Elkhorn boat ramps may provide more returns to the Sacramento River above the mouths of the Feather and American rivers than trucking releases to these locations or the Bay. Regardless, barging should provide substantially higher survival and returns to the upper river than river release of fish, especially in dry years. Barging test studies conducted by the Feather Hatchery program should be expanded to test potential benefits of Coleman salmon smolt barging.

Another measure that deserves testing is rearing Coleman fall-run fry off-site in Yolo Bypass rice fields. The higher survival and growth potential and earlier ocean entry of these smolts compared with smolts released at the hatchery, should increase the numbers of adult salmon available to the fisheries. Concerns include low returns to Coleman hatchery and straying of returning adults back to the Yolo Bypass. The State’s EcoRestore Program is planning fish passage improvement projects in the upper Bypass. Barging off-site-reared smolts to the Bay from nearby Knights Landing or Elkhorn boat ramp could potentially improve return rates to the hatchery and overall survival, especially in dry years

A third proven measure that is possibly more promising and readily implementable is improving downstream migration conditions for smolts released to the upper Sacramento River from the Coleman hatchery. Smolt survival and contribution to fisheries and adult returns to the hatchery are better when flow, turbidity, and water temperature conditions are good at the time of release and in the immediate weeks thereafter in the 200 miles downstream to the Bay. To a certain extent, the hatchery can time releases to river conditions (and does so when feasible). However, the timing of smolting and the whole rearing process necessitates a week 15-17 release window (late April to beginning of May). When conditions are optimal in these key weeks, survival and contribution rates of smolts released at Coleman are nearly as high as they are for smolts transported to the Bay. Such 1-3% survival (returns) would produce hundreds of thousands of adults, compared to just tens of thousands under poor conditions when there is just 0.2-0.5% survival (Table 1). A 3% survival would yield 360,000 adult salmon returns from 12 million hatchery smolts, as compared to only 12,000 returns under a 0.1% survival.

So what are good conditions in late April? Adequate stream flows are those necessary to meet existing water quality standards, water right permits requirements, and endangered species permit requirements in the upper 200 miles of river below Shasta Dam. Such prescriptions are basically minimum targets: keeping the upper river within the 56oF limit upstream of Red Bluff and the river downstream to the Delta at 68oF or less. These standards were put in place decades ago to protect beneficial uses, including salmon survival.

The problem is that these standards are both increasingly being ignored and violated, and are also proving inadequate in providing optimal smolt survival. Figure 1 shows that standards were violated at Red Bluff, even in 2017, a record water supply year. Figure 2 shows 2017 water temperatures at Wilkins Slough in the lower Sacramento River. Though water temperatures remained below 68oF (20oC) during the period shown, they reached above the 65oF (18oC) stress level for migrating juvenile salmon. Such high water temperatures place the smolts at much greater risk to predation.3 Even in this record water supply year, water was unnecessarily held in storage in Shasta Reservoir at the expense of Coleman and wild salmon smolt survival. When water contractor demands are low and Delta conditions are “in excess,” there is a tendency in all year types to maintain Shasta storage at the expense of lower river water temperature and Coleman smolt survival.

In addition to maintaining flows and water temperatures, a flow pulse through the lower river in the late April to early May period would likely improve survival. A flow pulse in drier years would provide higher transport rates, higher turbidity, and lower water temperatures, conditions that often occur in wetter, high survival years. A one week pulse that raised flows from the “dry” year 5000 cfs flow level to a 10,000 cfs level would use approximately 10,000 acre-ft per day, or about 70,000 acre-ft for a week. At Shasta Reservoir’s current storage level in excess of 4 million acre-ft, the water needed for a one week flow pulse would be less than 2% of the total storage for the year. Even for a multiyear drought year like 2015, the amount needed would be only 3 to 4% of total annual storage. While drought year pulses would need to be weighed against losses to the Shasta coldwater pool, a 1% improvement in dry-year survival would add 120,000 adult salmon from the 12 million smolts produced by the Colman hatchery. For a dry year or drought year sequence, the increase could be over 100% over current survival rates, and could allow a salmon fishing season when there might otherwise be none.

In summary, the salmon fishery collapses that occurred as a consequence of the 2007-2009 and 2012-2015 droughts could have been at least partially alleviated by improving survival of smolts produced at the Coleman hatchery. Compliance with spring water temperature standards in the lower Sacramento River would help greatly. When water supplies are adequate, spring flow pulses should be considered. Barging Coleman smolts to the Bay and off-site rearing in lower river floodplain habitats are additional measures to test in order to increase Coleman hatchery smolt survival and contributions to ocean and river fisheries.

Table 1. Survival (return) rates of Coleman hatchery fall run Chinook salmon release groups for a range of year types.
Source of survival data: http://www.rmpc.org.

Water Year Week 15-17 Conditions Smolt Survival4
1997 Wet Year Lower River conditions were deteriorating in April with flows falling from 7000 to 5000 cfs and water temperatures rising from 59oF (15oC) to 65oF (18oC). Week 15 – 0.8%
Week 16 – 0.3%
Week 17 – 0.2%
1998 Wet Year Lower River conditions were near optimal with 18,000 cfs flow and water temperature of 15oC. Week 17 – 0.9%
2002 Dry Year Lower River conditions degraded gradually from week 15 to week 17).  Flows in lower river fell from near 10,000 cfs to less than 5000 cfs during April.  Though water temperatures remained below 68oF (20 o C) during the period, they often reached above the 65oF (18 oC) stressful level for migrating juvenile salmon. Week 16 – 0.8%
Week 17 – 0.6%
2007 Critical Dry Year Lower River conditions were poor in weeks 16-17 with flows of 4000-5000 cfs and water temperatures of 19-21oC. Week 16 – 0.01%5
2008 Critical Dry Year Lower River conditions were poor with flows of 5000 cfs and water temperatures 16oC to 18oC in weeks 16-17, but reaching 20-22oC in week 18. Week 16 – 0.1%
Week 17 – 0.1%
2009 Critical Dry Year Lower River flow decreased from 7000 cfs to 5000 cfs in weeks 15-16, while water temperature rose from 15oC to 20oC.  Flow pulsed to 10,000 cfs in week 17 dropping water temperature to 15oC. Week 15 – 0.5%
Week 16 – 0.9%
2011 Wet Year Lower river flows in April were dropping sharply from 16,000 to 8,000 cfs, with water temperature rising from 15oC to 18oC. Week 15 – 2.2%
Week 16 – 1.5%
Week 17 – 1.2%

Figure 1. May 2017 flow and water temperature conditions in upper Sacramento River. Source: CDEC.

Figure 2. May 2017 water temperature in lower Sacramento River at Wilkins Slough. Source: CDEC.

  1. The Coleman Hatchery near Redding on Battle Creek is operated by the US Fish and Wildlife Service. The hatchery operates under the Central Valley Project as mitigation for Shasta Dam on the upper Sacramento River ↩
  2. http://calsport.org/fisheriesblog/?p=1703 ↩
  3. http://calsport.org/fisheriesblog/?p=878 ↩
  4. Survival rate is defined as percent of smolts that were subsequently collected as adults in fisheries, spawning surveys, and at Central Valley hatcheries. Average rate of multiple groups is shown. ↩
  5. Poor ocean conditions in 2007-2009 likely contributed to poor survival. ↩

Splittail Status end-of-June 2017

Posted on by

Last time I posted on splittail, it appeared that the species remained relatively abundant (though declining) in its core population centers in the Bay. I was concerned about population recruitment during the 2012-2015 drought and whether there were sufficient adults remaining to bring about a strong brood year in wet year 2017. The traditional summer and fall surveys will be the best indicator of success. At the end of spring, the best interim indicator is splittail salvage at south Delta SWP and CVP export facilities. In wet years, south Delta export salvage likely best reflects San Joaquin River splittail production.

I compare salvage in 2011 with 2017 in Figures 1 and 2 for the SWP and CVP, respectively. These were the only wet years since 2006. Wet years provide good spawning and rearing conditions for splittail. These conditions often create strong year classes of juvenile and adult splittail as shown in summer and fall fish surveys in the Delta and the Bay.

Though the density of juvenile splittail in salvage is lower in 2017 than 2011, winter and early spring flows were higher in 2017, which could have led to broader dispersal. Very high late winter and early spring flows in the lower Sacramento River system including the Yolo Bypass may have transported north-of-Delta splittail production directly to the Bay, bypassing the south Delta and its export facilities. Spring flows in the two years were similar in magnitude when young splittail traditionally move downstream through the Delta toward the Bay. It remains to be seen whether the difference in salvage plays out as a discrepancy in recruitment in the Bay populations. Local spawning recruitment in the Napa and Petaluma rivers and in Suisun Bay/Marsh could be strong in years like 2017 and could make up for lower recruitment from the Sacramento and San Joaquin river valleys. The primary concern is long term trends in the core adult population centers in the Bay that for now remain strong.

Splittail Salvage at SWP Byron Facility

Figure 1. Splittail salvage density (number per 10,000 cubic meters exported) at State Water Project Delta export facility in May and June 2011 and 2017.

Splittail Salvage at CVP Tracy Facility

Figure 2. Splittail salvage density (number per 10,000 cubic meters exported) at Central Valley Project Delta export facility in May and June 2011 and 2017.

Delta Status End of June 2017

Posted on by

Despite the fact that it is a record wet year with abundant spring snowmelt, early summer conditions in the Delta in 2017 are not looking good.  Rapidly falling Delta inflows and a late June heat wave have led to salt water intrusion and extremely warm water temperatures detrimental to salmon and smelt throughout the Delta.

Notably, lower Sacramento River flows at Wilkins Slough upstream of the mouth of the Feather River are down about a third compared to the last Wet year, 2011 (Figure 1).  Flow is only about 7000 cfs and water temperatures are 73-75°F, well above the water quality standard of 68°F.  Winter-run and spring-run adult salmon will not move up the river at these temperatures.  Why is flow so low?  Good question.  Shasta is nearly full but releases are down about a third for a wet year at 8000 cfs.  In contrast, the San Joaquin River flow coming into the Delta near Stockton is 13,000-15,000 cfs, with water temperatures of 71-73°F.

Feather River flow contributions to the Sacramento River are very low (Figure 2).  Yuba and American River flow contributions remain strong at about 4000 cfs each.

Overall Delta outflow in late spring 2017 is lower than Wet year 2011 (Figure 3).  Delta inflow is approximately 34,000 cfs, with about equal contribution from the Sacramento and San Joaquin rivers. Delta exports have been maximum through June at 11,400 cfs.  With in-Delta use taken into account, Delta outflow is estimated at 19,000-21,000 cfs. (Note: USGS measured outflow about 14,000 cfs with tides taken into account on June 22.)

With sharply falling Delta inflow and outflow, high exports, and the heat wave, the Delta is unusually warm at 72-75°F. Such temperatures are detrimental to juvenile smelt, salmon, and sturgeon survival.  Juvenile salmon have been present in the Delta well into June on their seaward migrations (Figure 4).

 With falling Delta inflow and high exports, the Delta is stagnating and salt water is intruding at the west end at Chipps Island (Figure 5).  The Low Salinity Zone with the few Longfin and Delta smelt that are left is moving into the Delta on incoming tides.  The water temperature at the head of the LSZ is already 72°F (Figure 6).  Higher temperatures would be very detrimental to surviving smelt and seaward-moving juvenile salmon.  The further east the LSZ moves, the warmer it usually becomes.

There is a consistent late spring pattern in the operation of State Water Project and Central Valley Water Project in which they cut reservoir releases while exporting the remnant freshwater pool in the Delta.  Even in this very wet year we are again witnessing this water supply control strategy.  The problem is the rivers get too warm even to the point of violating water quality standards.  With less water and warmer water entering the Delta, the Delta also becomes too warm.  Delta water quality standards and endangered species permits are supposed to keep this from happening.  Come July 1, conditions will only get worse, especially as snowmelt declines and San Joaquin flows drop sharply.

What can be done?  Both Shasta and Oroville reservoir releases are lower than normal.  Just keeping their cold-water releases near normal and allowing the flows to pass through the Delta would nearly fix the problem.  Exports in the 1970’s and 1980’s were limited to 6000-9000 cfs in June-July of Wet years.  Reducing the present export level of 11,000 cfs would also help.  These would be very reasonable actions given present water supplies in the Central Valley.

Figure 1. Flow in the lower Sacramento River at Wilkins Slough in late spring of 2011 and 2017.

Figure 2. Lower Feather River flow at Gridley upstream of the mouth of the Yuba River.

Figure 3. Delta outflow in late spring 2011 and 2017.

 

Figure 4. Salmon salvage at Delta fish facilities in June 2017. Source: https://www.wildlife.ca.gov/Conservation/Delta/Salvage-Monitoring

Figure 5. Salinity (EC) at Mallard Island gage near Chipps Island (eastern end of Suisun Bay) in June 2017.

Figure 6. Water temperature at Mallard Island gage near Chipps Island (eastern end of Suisun Bay) in June 2017.