Addendum to the State Drought Plan – August 31, 2021, Part 3: Reclamation’s Bad Plan Left Fish Agencies with September Hobson’s Choice

Earlier this summer, the Bureau of Reclamation’s operations of Shasta Reservoir, under its Drought Plan jointly developed with the California Department of Water Resources (DWR), caused high water temperatures that delayed spawning of winter-run Chinook salmon to early summer (mid-June through mid-July).1 Winter-run salmon leave the redds after 2-3 months, which in 2021 will mean a mid-August through September peak emergence.

In their Addendum to the State Water Project and Central Valley Project Drought Contingency Plan issued August 31, 2021, Reclamation and DWR state how an increase in September releases responded to a request from fisheries agencies:

In the July Drought Plan update, Reclamation’s forecast for releases to the Sacramento River were 7,850 cfs in August, ramping down to a monthly average of 5,200 cfs in September, and then going back up to 7,550 cfs in October to move the transfer water referenced above. In late August, the fishery agencies reviewed updated data indicating that a flow of approximately 6,800 cfs was needed through early-October to protect several remaining winter-run Chinook salmon redds. As a result, Reclamation modified its previous plan and held releases at 6,800 starting August 26.

Not so fast. In 2021, as in 2014, Reclamation cast the die early in the year, releasing too much water that was too warm until late June (Figures 1 and 2). That was Reclamation’s call, not the choice of the fish agencies. The agencies know that in drought year 2014, Reclamation also maintained both high flow releases and high water temperatures early in the summer, and that therefore the winter-run salmon spawned late. The agencies also know that a drop the water level 2-3 feet at the beginning of September 2014 (Figures 1 and 2) proved catastrophic to eggs and alevin still in the redds. Such drops in water level, with most redds in 1-3 ft of water, cause dewatering, reduced inter-redd water flow, sedimentation within the redd, lower dissolved oxygen, higher redd water temperatures, early hatching, direct egg/embryo mortality, and restricted fry movement within and emergence from redds.

The planned drop in early September of 2-3 feet in water level, part of the original 2021 Drought Plan, was a bad part of bad plan from the get-go. In 2015, Reclamation at least tried to avoid the drop by keeping releases lower throughout the summer (Figures 1 and 2). The August Addendum insinuates that added loss of storage in September-October to maintain higher flow/stage was the result of fishery agency review, when the agencies never wanted nor originally approved the September drop in river flow. The steady flow/stages in 2015 (Figures 1 and 2) was the appropriate prescription.

Just as it was a happy circumstance for the Sacramento River Settlement Contractors that Reclamation delivered them too much water north of the Delta early in the year, it was a happy circumstance for Reclamation and the Settlement Contractors that their planned water transfers of about 200 thousand acre-feet (TAF) to buyers south of the Delta just happened to be ready to go just as the drop planned earlier in the summer was scheduled to happen. Transfer water in a market where prices are north of $1000/AF is the mother’s milk of the change in September Shasta operations (Figure 3).

The accelerated schedule of transfers from Shasta storage also reduces the opportunity for the State Water Board or its Executive Director to wake up and smell the receding predictions for the reservoir’s receding shoreline. The tables at the end of the August Addendum now predict end-of-November storage in Shasta to be an unprecedented 729 TAF, down from the July Addendum’s prediction of 849 TAF. The only numbers that have maintained relative consistency throughout the summer 2021 Sacramento River debacle are the levels of deliveries and transfers. That consistency has been matched and enabled by the silence of the Water Board.

In summary, the original 2021 Drought Plan did not address the real risk of redd stranding that proved devastating for the winter-run salmon spawn in summer 2014. The July-August 2021 stage drop was bad enough and should have been avoided, given that high water temperatures delayed the spawn of winter-run to late June. The fish agencies were cornered into choosing between a large September 1 stage drop in a bad original plan and the buy-now-but-pay-later option of maintaining higher flows through September. The additional drain on Shasta storage and Reclamation’s increasing inability to maintain cold water releases through October show the folly and poor design of the original Drought Plan.

This post is part 3 in a series on DWR and Reclamation’s August Addendum to the 2021 Drought Plan.

Figure 1. River stage below Keswick Dam June-October 2014, 2015, and 2021.

Figure 2. River stage at Bend Bridge, 60 miles below Keswick Dam June-October 2014, 2015, and 2021.

Figure 3: Reclamation’s Delta Exports August 15-September 15, 2021.

Addendum to the State Drought Plan — August 31, 2021, Part 1: the Art of the Euphemism

The California Department of Water Resources (DWR) and the U.S. Bureau of Reclamation (Reclamation) released a Central Valley Drought Contingency Plan Update on August 31, 2021, stating:: “Project operations are still tracking with the operations forecast included in the July Drought Plan addendum. August has been fairly typical, with operations primarily controlled by system-wide depletions and Delta salinity.”  This is like a dispatch from the captain of the Titanic saying: the ship was tracking course since the last report, and yes, it hit the iceberg.  As is fairly typical under such circumstances, it sunk, primarily due to the hole in the hull.

The “depletions” that caused the current gaping hole in Shasta Reservoir’s storage and the resulting lethal downstream water temperatures, to reach full effect in September, didn’t just happen.  These glibly described “depletions” are primarily the excessive deliveries to Sacramento River Settlement Contractors to which this blog, CSPA, and others have been vociferously objecting since March.  And, of course, what is sunk is not the good ship Reclamation.  It is the year’s cohorts of Sacramento River salmon, just like in the disasters of 2014 and 2015.

Shasta-Keswick Storage Releases to the Upper Sacramento River

In 2021, Reclamation has not heeded the lessons learned in the 2013-2015 drought.  In 2021, Reclamation has not even implemented the feeble salmon-saving drought actions it applied in 2014 and 2015.

  1. April-May Keswick storage releases were higher in 2021 than 2014 (+257 TAF) and 2015 (+185 TAF) (Figure 1). Reclamation restricted releases in 2014 and 2015 in April-May to preserve Shasta’s cold-water pool.  It did no such thing in 2021.
  2. The higher releases in 2021 led to depleted storage in Shasta Reservoir (Figure 2). Storage at the end of May 2021 was 200 TAF lower than in May 2014, after having been 200 TAF higher at the beginning of April.
  3. The measures to maintain steady flow/stage and water temperature prescribed for drought year 2015 were not applied in 2021. In 2021 operations reverted to the 2014 regime, or worse.

Spawning Conditions for Winter Run Salmon

Winter-run salmon spawn from April to August, with a June-July peak in the ten miles of river downstream of Keswick Dam.  Early season (April-May) flow and water temperature conditions were erratic in 2014, 2015, and 2021 (Figures 1-4).  Rising flows and water temperatures stimulate the spawning migration and maturation leading up to the spawn.  Water temperature above 65ºF hinder migrations and stress adult spawners.  Water temperatures above 60ºF delay spawning and stress eggs in female salmon and eggs/embryos in redds.

  1. Conditions in 2014 proved devastating for the salmon spawn because of high water temperatures in late summer as Reclamation lost access to Shasta’s cold-water pool due to low storage. In addition,  a late summer drop of 2-3 feet in the stage height of the Sacramento River downstream of Keswick Dam caused spawning interruption and redd stranding (Figure 3).
  2. Despite concerted efforts in 2015 to retain storage, to maintain steady flows (and stage), and to sustain colder water releases, water temperature proved too high (>55ºF) for good egg/embryo survival. The lesson learned led to the current target for good survival of <53ºF in Keswick releases.
  3. Operations in 2021 were devastating, starting with high spring water temperatures, followed by a short period of good conditions in late June designed to stimulate spawning, before higher water temperature (Figure 4) and falling stage height greeted later winter-run spawners and egg/embryos/fry in redds.

Migration Conditions for Adult Salmon in Lower Sacramento River

Water temperatures in the lower Sacramento River 100-200 miles downstream of Shasta Dam remained far from typical in 2021 (Figure 5).  For the most part, water temperature from May through August were above the minimum stress level of 68ºF, and above the 72ºF avoidance level for weeks at a time.  These conditions not only affected the late migration of winter-run salmon, but also that of the spring-run (in spring) and fall-run (in summer) who spawn in early fall.

Summary

In summary, Reclamation’s operations of Shasta Reservoir have been as bad in 2021 as they were in 2014 and 2015, or worse.

Future posts will discuss more aspects of the failures of Reclamation’s Shasta operations in 2021.

Figure 1. Water releases from Keswick Dam (river mile 300) to the lower Sacramento River near Redding CA, April-August 2014, 2015, and 2021.

Figure 2. Shasta Reservoir storage (acre-feet) April-August in 2014, 2015, and 2021.

Figure 3. River Stage in Sacramento River below Keswick Dam April-August in 2014, 2015, and 2021.

Figure 4. Water temperature in Sacramento River below Keswick Dam April-August 2014, 2015, and 2021.

Figure 5. Water temperature in the lower Sacramento River at Wilkins Slough (river mile 120) May-August 2021, along with average for past 13 years. Note that the State’s year-round water quality standard for the lower Sacramento River is for water temperature to remain below 68ºF.

Sites Reservoir —
Potential Benefits for Fish,
Potential to Worsen Conditions for Fish
Working Presumption: Thumbs Down

The proposed Sites Reservoir1 would be a new off-stream storage reservoir covering 12,000 -14,000 surface acres with 1.8 million acre-ft of storage capacity on the west side of the Sacramento Valley (Figure 1). The project would capture and store unregulated Sacramento River winter-spring runoff and some water previously stored in Shasta Reservoir. The diversion capacity to the reservoir would be 5400-6500 cfs, supplied by two existing river diversions (up to 1800 cfs at Red Bluff; up to 2100 cfs at Hamilton City) and a new diversion near Colusa (proponents are evaluating alternative capacities of 1500 and 3000 cfs, in addition to the currently preferred capacity of 2000 cfs). The Sites Authority webpage estimates that it could have diverted over 1 Million acre-ft to storage in Sites in 2018 and 1.8 Million acre-ft to storage in 2017; these figures assume bypass flow requirements at the diversion points and at Freeport, and sufficient storage capacity in the reservoir. The Draft Environmental Impact Report/Environmental Impact Statement (DEIR/DEIS) for the Sites Reservoir Project estimates the average annual diversion to Sites storage at about 500,000 acre-ft; actual diversions would vary depending on hydrology and regulatory constraints.

As an off-stream storage reservoir, Sites would store water behind a dam that is not on a major waterway. Water diverted to the reservoir would be pumped into canals from the Sacramento River, and then pumped into the storage reservoir from small holding reservoirs on the canals. The two existing diversions that would fill Sites have modern fish screening facilities. As currently envisioned, a pump-back hydroelectric operation would allow partial recovery of pumping costs.

The Sites project has potential benefits for fish, but also the potential to worsen conditions for fish.

Potential Benefits for Fish

  1. Under current operations, existing irrigation diversions on the Sacramento River draw water primarily in spring and summer via several major canal systems on the west side of the Sacramento Valley. These diversions draw mainly on water that was previously stored in Shasta Reservoir and released to the Sacramento River in part to keep river water temperatures cool. Shasta Reservoir’s cold-water pool varies in volume depending on storage and other factors, and can run out if it is not managed carefully. If the cold-water pool is depleted at the end of the summer, this threatens the viability of winter-run salmon. Under current operations, spring and summer irrigation diversions from the Sacramento River also cut flow and raise water temperatures in the lower river, which harms salmon, steelhead and sturgeon. Water diverted to storage in Sites in the winter could substitute for some of the spring and summer irrigation deliveries that currently come from Shasta. A greater percentage of water released from Shasta in spring and summer could then flow all the way to the Delta. More water could also be retained in Shasta Reservoir to protect the Shasta cold-water pool into the fall and as carryover for the following year.
  2. If more water were delivered to the Delta from Shasta Reservoir in the spring and summer, less water would theoretically be needed from Folsom and Oroville reservoirs to meet Delta water quality, outflow and other requirements. This could allow more targeted releases of water into the lower American and lower Feather rivers to protect fish in those waters. It could also allow better maintenance of cold-water pools and greater carryover storage in Folsom and Oroville, also very important for the respective fisheries downstream.
  3. Water stored in Sites could be delivered directly to the Delta via the Colusa Basin Drain (CBD) system and Yolo Bypass, reducing outflow demands from other Valley reservoirs. Water delivered directly to the Delta from Sites would be of higher potential productivity and could stimulate winter-spring Bay-Delta plankton blooms that would benefit Delta native fishes.

Potential to Worsen Conditions for Fish

  1. The proposal includes a new point of diversion on the Sacramento River with a capacity to divert 2000 cfs. This would give the project higher diversion capacity and the capability of diverting tributary runoff that would otherwise be unavailable to the two upper river diversions that now enters the Delta. This diversion would also affect flows and water temperatures in the lower Sacramento River, and subject migrating juvenile salmon, sturgeon, and steelhead to a third large screening facility. The new point of diversion would be particularly problematic if it diverted water outside the peak runoff season (late fall through spring).
  2. The new diversion and the reoperation of canal intakes at Red Bluff and Hamilton City to divert water in winter would compete for water with Delta diversions and would affect Delta outflow to the Bay.
  3. Water deliveries and hydropower releases from Sites Reservoir to the lower river at the new diversion site could affect water quality in the lower Sacramento River.
  4. With available winter off-stream storage, the existing diversions at Red Bluff and Hamilton City would be capable of diverting uncontrolled flows from tributaries that have otherwise remained relatively untouched down to the Delta.
  5. The greater diversion capacity may increase demands on Shasta storage and will increase diversion of uncontrolled tributary flows, further compromising fishes in the Sacramento River and the Bay-Delta.
  6. A small but potentially significant amount of water supply stored in Sites Reservoir would be lost to evaporation and groundwater seepage.

Above all, there is too much unknown to evaluate how Sites would affect fish.

As is the case for most proposed water supply projects, the project description in the draft DEIR/DEIS for Sites describes several potential configurations of project infrastructure and a description of proposed constraints. The DEIR/DEIS does not evaluate different constraints, such as different bypass flow requirements past each point of diversion; the DEIR/DEIS only evaluates one value for each point. In spite of numerous requests that the DEIR/DEIS evaluate project diversions with more stringent Delta flow and water quality requirements than the existing inadequate ones, the DEIR/DEIS only evaluates project yield with existing Delta constraints.

The benefit side is even more vague and conceptual. The entire construct of hypothetical Sites benefits would in fact require a new type of proscriptive rules and enforcement mechanisms that would be unprecedented for California water projects. There is simply no clue in any of the Sites literature what those rules would be or even could be.

The project description places no numbers on how much water stored in Sites the project’s operators would dedicate to actions designed to benefit fish. The project description defines no decision-making process for dedicating water to fish, other than to say that on an overarching basis fish agencies will decide. The project description defines no way in which project operators will apportion water for fish against water for water supply. For all the offsets that seem to comprise the lion’s share of fish benefits, the project description does not say how water from Sites will generate improvements in operation of state or federal reservoirs, or whether it will be Sites operators or state and federal operators who make the calls.

Then there is the question of whether there would be any offsets at all. There is no assurance that there will be any decreases at all in water use from Shasta or from other state and federal reservoirs. Water freed up by using Sites to meet Sacramento Valley water supply could simply allow Sac Valley water users to irrigate more land or sell more water for export at the Delta pumps. The DEIR/DEIS proposes no mechanism of enforcing offsets: who would regulate the project’s use of water, who would manage the interaction between Sites water and water from Shasta, Oroville, Folsom and perhaps Trinity reservoirs, and how and against whom any requirements would be enforced.

There are other problems. A shift to winter-spring diversions and use of canal systems would potentially change groundwater recharge and use patterns in the Sacramento Valley. The project would compete for water available to the proposed WaterFix Twin Tunnels project in the Delta. Sites and WaterFix have their “sights” on the heretofore untouched tributary inflows that are also protected by Delta export OMR limits so the flows reach the Bay. There will be a big fight over this uncontrolled water that now makes up a significant portion of the Bay’s freshwater input in drier years. Both projects have claimed future benefits of the same pot of water.

Conclusion

There are potential benefits from Sites project’s main features to Central Valley fishes, including salmon, steelhead, sturgeon, smelt, and striped bass. Most of the benefits would result from switching the diversion time period of the two existing upper river diversions and Shasta reservoir releases to these diversions. The added new diversion and increase in winter diversions will at important times reduce Sacramento River flow and Bay-Delta inflow and outflow, harming fish in certain but sometimes hard to quantify amounts.

Past water developments in the Central Valley have overwhelmingly made conditions for fish worse. The Sites project proponents claim that their project will be different. These proponents have not done themselves, the public, or public policy any favors by relying on generalities and politics as the centerpieces of their efforts to advance their project. At this time, there are too many unknowns to meaningfully evaluate the possibility that benefits might outweigh the harm and justify the costs. In the meantime, it is a reasonable working presumption that the Sites project will worsen conditions for fish as well.

Figure 1. Proposed Sites Reservoir and associated infrastructure on west side of the Sacramento Valley.

More on Delta Smelt Tidal Surfing

The last post about risk to Delta smelt was on January 9. Adult smelt migrate into the Delta from the Bay in winter to spawn. They take advantage of the flood tide to move upstream. However, with flood flows as high as 100,000 cfs entering the north Delta from the Sacramento River, the Yolo Bypass, and Georgiana Slough in mid- to late January 2017, there are no flood tides to ride into the north Delta spawning areas.

The only option for the adult smelt is thus to ride the incoming tide up the San Joaquin River into the central and south Delta (Figure 1). South Delta export pumping is currently at 14,000 cfs, near maximum capacity, using four rarely used auxiliary pumps. This pumping increases the pull of the incoming tide, reducing the effect of the inflow from the San Joaquin, Calaveras, Mokelumne, and Cosumnes rivers. While Delta inflow from these rivers is relatively high (Figures 2-5), it does not offset the influence of the incoming tide as does the inflow from the Sacramento.

Net tidal flows in lower Old and Middle Rivers (OMR flows) remain at the allowed limit of -5000 cfs, consistent with the smelt Biological Opinion. Several adult Delta smelt were salvaged at the export facilities in mid-January. 1 This scenario is considered a “high risk” to Delta smelt by the Smelt Working Group, because of the continuing risk that the pumps will draw or attract adult smelt into the central Delta and subsequently into the south Delta.

Under lower San Joaquin River flows, the maximum allowed export pumping is 11,400 cfs. High San Joaquin River inflow allows exports of 14,000 cfs that do not generate OMR flows more negative than -5000 cfs. The theoretical benefit of high San Joaquin River flows is that it should keep flow into the central and south Delta moving westward. But a large portion of that inflow is diverted south into the Head of Old River toward the pumping plants (Figure 6).

Figure 1. Approximate flood tide flow in cubic feet per second in mid to late January 2016. Blue arrows represent high Sacramento River, San Joaquin River and Mokelumne River flows (during flood tides). Red arrows depict negative flows of incoming tides. Note the south Delta incoming tide of -20,000 cfs would be less if not for the 14,000 cfs export rate at the south Delta pumping plants.

Figure 1. Approximate flood tide flow in cubic feet per second in mid to late January 2017. Blue arrows represent high Sacramento River, San Joaquin River and Mokelumne River flows (during flood tides). Red arrows depict negative flows of incoming tides. Note the south Delta incoming tide of -20,000 cfs would be less if not for the 14,000 cfs export rate at the south Delta pumping plants.

Figure 2. San Joaquin River flow at Mossdale at the head of the Delta upstream of Stockton and the Head of Old River. Note that on Jan 6 when flow reached about 6,000 cfs, the tidal signal dissipated when flow overcame the tidal forces.

Figure 2. San Joaquin River flow at Mossdale at the head of the Delta upstream of Stockton and the Head of Old River. Note that on Jan 6 when flow reached about 6,000 cfs, the tidal signal dissipated when flow overcame the tidal forces.

Figure 3: Flow from the Calaveras River, upstream of the Delta. The Calaveras enters the Delta at Stockton.

Figure 3: Flow from the Calaveras River, upstream of the Delta. The Calaveras enters the Delta at Stockton.

Figure 4. Release from Camanche Dam to the Mokelumne River. CDEC does not show flow values for the Mokelumne at gages further downstream. The Mokelumne enters the Delta near Jersey Point.

Figure 4. Release from Camanche Dam to the Mokelumne River. CDEC does not show flow values for the Mokelumne at gages further downstream. The Mokelumne enters the Delta near Jersey Point.

Figure 5. Cosumnes River flow well upstream of the Delta. Much of the high flow peaks enters the river’s connected floodplain, roughly between Lodi and Elk Grove, and does not flow immediately to the Delta. Flows in the Cosumnes enter the Mokelumne before passing into the Delta

Figure 5. Cosumnes River flow well upstream of the Delta. Much of the high flow peaks enters the river’s connected floodplain, roughly between Lodi and Elk Grove, and does not flow immediately to the Delta. Flows in the Cosumnes enter the Mokelumne before passing into the Delta

 Figure 6. Flow entering the entrance to Old River from the San Joaquin River near Stockton.


Figure 6. Flow entering the entrance to Old River from the San Joaquin River near Stockton.

  1. https://www.usbr.gov/mp/cvo/vungvari/dsmeltsplitdly.pdf Note: website has changed to this new site.

What Caused the Impending Extinction of Delta Smelt?

CSPA’s fisheries biologist Tom Cannon gave a presentation entitled “Contributing Cause of Smelt Decline: Water Exports” at a symposium on March 29, 2016 at UC Davis. The theme of the conference, sponsored by the Delta Stewardship Council, was: “Delta and Longfin Smelt: Is Extinction Inevitable?”

In his presentation, Tom put forth the hypothesis that the cause of the probable extinction of Delta smelt was the commencement of operation of the State Water Project’s Banks Pumping Plant in the mid-1970s. When Banks came on line, South Delta exports tripled, going from 2 million acre-feet to 6 million acre-feet per year. Tom’s hypothesis is that the mechanism of likely extinction was entrainment of Delta Smelt into the inflow to State and Federal South Delta pumping plants: exports.

The presentation’s first slide shows the familiar long-term Fall Midwater Trawl Index (Figure 1). Tom emphasized the sharp drop in the Index in 1981 (red circle in Figure 1), the first dry year of operations under the 1978 Delta Plan (water quality standards limiting operations of the Delta pumping plants). He noted that the decline likely started in the mid-1970s, but was most severe in 1981. There were recovery periods in the non-drought years of the 1990’s and 2010-2011. However, in 2001-2005, smelt and other Delta species crashed, a period now known as the “Pelagic Organism Decline,” or POD. Following a mild recovery in the wet year 2011, Delta smelt collapsed to record low indices in 2014 and 2015 (indices of 9 and 7, respectively, not shown in Figure 1).

Other slides depict (1) the huge losses of adult smelt as indexed by January1 salvage numbers in 1981 (Figure 2), and (2) the salvage counts of juvenile Delta smelt in spring 1981 (Figure 3). The total salvage for January 1981 alone was over 10,000 adult Delta smelt, which compares to a total of 56 in January 2015 and 12 in January 2016. The total juvenile Delta smelt salvage in spring 1981 exceeded 100,000; in 2015, it was 4.

An example of salvage during the 2001-2005 POD is winter-spring salvage in 2003 (Figure 4). Tom attributes the POD decline to the tens of thousands of Delta smelt lost to entrainment in winter and spring, including a likely large number of non-detected larvae under conditions of maximum exports.

According to Tom, export entrainment is the primary causal factor for the death spiral of Delta smelt, not low outflow. There were relatively high or improved smelt abundance indices in 1972, 1990, and 1991 (see Figure 1), which were all years with low outflows but also low exports. This is not to say, however, that low outflows are not also factors that contribute to high entrainment (Figures 2 and 3).

Tom concludes that Delta smelt are virtually extinct because their adult spawning numbers are insufficient to provide recovery even under 2016’s good (wet) conditions. Adult numbers are simply too low to produce sufficient offspring (Figure 5). The proof will come this spring, summer, and fall when indices of Delta smelt juveniles will likely remain critically low and not reach 2010 or 2011 levels, the last years when habitat conditions were favorable.

Tom Cannon Presentation – Contributing Cause of Smelt Decline: Water Exports

Figure 1. Fall Midwater Trawl Index for Delta smelt 1967-2013. (Source: CDFW.)

Figure 1. Fall Midwater Trawl Index for Delta smelt 1967-2013. (Source: CDFW.)

Figure 2. January salvage of adult Delta smelt at South Delta export pumps in 1981. Also shown is export rate (cfs) and Delta outflow (cfs). The maximum allowed export rate is 11,400 cfs. (Data Source: CDFW.)

Figure 2. January salvage of adult Delta smelt at South Delta export pumps in 1981. Also shown is export rate (cfs) and Delta outflow (cfs). The maximum allowed export rate is 11,400 cfs. (Data Source: CDFW.)

Figure 3. Spring salvage of juvenile Delta smelt at South Delta export pumps in 1981. Delta smelt juveniles begin reaching salvageable size (>20 mm) in early May. Also shown is export rate (cfs) and Delta outflow (cfs). The maximum allowed exportsrate is 11,400 cfs. (Data Source: CDFW)

Figure 3. Spring salvage of juvenile Delta smelt at South Delta export pumps in 1981. Delta smelt juveniles begin reaching salvageable size (>20 mm) in early May. Also shown is export rate (cfs) and Delta outflow (cfs). The maximum allowed exportsrate is 11,400 cfs. (Data Source: CDFW)

Figure 4. Winter-spring salvage of Delta smelt at south Delta export pumps in 2003. Delta smelt young begin reaching salvageable size (>20 mm) in early May. Also shown is export rate (acre-feet per day) by pumping plant. The maximum allowed export rate is 11,400 cfs (about 23,000 acre-feet per day). (Data Source: CDFW). Winter salvage is primarily adult smelt. Spring salvage is predominantly juvenile smelt (>20 mm). April entrainment of 5-15 mm larval smelt is not accounted for at salvage facilities, because they pass undetected through salvage screens.

Figure 4. Winter-spring salvage of Delta smelt at south Delta export pumps in 2003. Delta smelt young begin reaching salvageable size (>20 mm) in early May. Also shown is export rate (acre-feet per day) by pumping plant. The maximum allowed export rate is 11,400 cfs (about 23,000 acre-feet per day). (Data Source: CDFW). Winter salvage is primarily adult smelt. Spring salvage is predominantly juvenile smelt (>20 mm). April entrainment of 5-15 mm larval smelt is not accounted for at salvage facilities, because they pass undetected through salvage screens.

Figure 5. Index of adult Delta smelt spawner abundance from winter Kodiak Trawl Survey 2002-2016.

Figure 5. Index of adult Delta smelt spawner abundance from winter Kodiak Trawl Survey 2002-2016.

  1. Salvage collections are notoriously inefficient on small fish entrained into the pumping plants. Predation loss before entering the salvage facilities has been estimated to be higher than 90%.