I fully support implementation in 2024 of the Fall X2 action prescribed in the biological opinion for Delta smelt. Furthermore, I support maintaining Delta Outflow at 10,000-12,000 cfs year-round[1] in all water year types to protect Delta smelt and longfin smelt. The compelling reason for such action is to maintain the low salinity zone (LSZ) and the head of that zone downstream of the confluence of the Sacramento and San Joaquin rivers in the western Delta, on an average-daily or tidally-filtered basis (Figures 1 and 2).
Such action will require approximately 10,000-12,000 cfs daily average Delta outflow (Figure 3). Such action would ensure the LSZ is maintained downstream of the Delta within Suisun Bay, Suisun Marsh, and Montezuma Slough – conditions necessary to protect listed Delta and longfin smelt populations. Otherwise allowing the LSZ to enter the Delta subjects the pre-spawn staging of the smelts (Figures 4 and 5) to entrainment into Delta water exports and the vagaries of Delta habitat (poor water quality and food supply, as well as lower turbidity and higher predation). Failure to maintain the X2 in Suisun Bay below the confluence also undermines the integrity of the LSZ critical habitat of the smelt in future months. My conclusions are further amplified in prior comments in support of the Fall X2 (https://calsport.org/fisheriesblog/?p=2940).
In conclusion, failure to implement Fall X2 will have an adverse impact on Delta smelt and longfin smelt and their critical LSZ habitat.
Figure 1. Water temperature and salinity of eastern Suisun Bay near Pittsburg June-September 2024.
Figure 2. . Hourly and tidally filtered salinity of eastern Suisun Bay near Collinsville August-September 2024. Note X2 is approximately 2 psu (ppt)
Figure 3. Daily Delta outflow August-October in 2023, 2024, and average 2014-2023. Note application of Fall X2 in September 2023 (> 8,000 cfs).
Figure 4. October 2023 fall midwater trawl survey catch of longfin smelt.
Figure 5. October 2011 fall midwater trawl survey catch of Delta smelt.
[1] Except in critical drought years when exports are minimum due to minimum available water supply.
In a June 2024 post, I hypothesized factors controlling the white sturgeon population in San Francisco Bay-Estuary. I concluded the major factor controlling the adult stock size was periodic recruitment of juvenile sturgeon from successful spring spawning and early rearing in the lower Sacramento River. Successful recruitment only occurs in the wettest years, when there are higher streamflows and cooler water temperatures.
Recruitment of young white sturgeon in significant numbers has only occurred in three years since 2010: 2011, 2017, and 2023. Recruitment in 2024, an above normal water year, is likely to be poor. Production of young sturgeon is likely of function of attraction of spawners from San Francisco Bay (to high winter-spring river flows – good in 2024), good spawning conditions (streamflow and water temperatures – good in 2024), and good early rearing and transport conditions in the lower Sacramento River and the north and central Delta (streamflow and water temperatures – poor in 2024).
The adult spawning stock size may not be as important as spawning conditions, given strong recruitment in wet year 2023 under a very low stock abundance (observed Bay die-off in summer of critical drought year 2022).
There are a number of measures that hold promise to protect and enhance adult stock numbers, recruitment, and survival of white sturgeon.
Spawning Conditions
Flows in the lower Sacramento River (Wilkins gage) should be 8,000 to 10,000 cfs or higher in spring.
Flow in the lower Sacramento River (Wilkins Slough) should be at least 8,000-10,000 cfs.
Early Rearing and Juvenile Transport
Sacramento River inflows to the Delta should be at least 20,000 cfs in spring.
Flow from the lower Sacramento River into the Delta (Freeport) should be at least 20,000 cfs in spring and early summer (April-July).
Delta Conditions
The net flow in the lower Sacramento River channel downstream of the entrance to Georgianna Slough should be at least 10,000 cfs in spring and early summer (April-July). This will require total Delta diversions, including local agricultural diversions and exports by the State Water Project (SWP) and Central Valley Project (CVP), to be limited to approximately 10,000 cfs.
Flow in the lower Sacramento River in the Delta below Georgianna Slough should be at least 10,000 cfs in spring and early summer (April-July).
White sturgeon recruitment is best assessed at fish salvage facilities at the water project south Delta export pumps. Young sturgeon produced in the lower Sacramento River reach the Delta in early summer as shown here in 2023. Note the high export levels of 20,000 acre-feet per day (approximately 10,000 cfs; in this figure, SWP exports are shown behind CVP exports).
Bay Conditions
Delta outflow to the Bay should be at least 10,000 cfs from spring to early fall (April-October).
Delta outflow to the Bay (DTO) and Rio Vista water temperature May-Oct, 2021-2024. Recommended Delta Outflow is a minimum 10,000 cfs (purple line).
Minimize Sturgeon Adult Harvest and Pre-Adult Fishing Mortality
Sturgeon sport fishing should be limited to the Bay only, with catch-and-release regulations, with the following further considerations:
Fishing for sturgeon should be closed in the east Bay or north Bay if daily maximum water temperatures are expected to exceed 65ºF (18ºC) in any open water portion gage locations in either Bay portions (possible from late spring through early fall).
CDFW could allow limited harvest through short-term regulations, limited by slot (length range) and number. (Note that slot harvest in 2024 would allow a small harvest of broodyear 2011 white sturgeon, the most recent abundant broodyear in the adult population).
Under such restrictions, the effects of sport fishing on the sturgeon population would be minimal.
In addition, sturgeon collected at south Delta export salvage facilities should be transported to an appropriate location in the Bay for release (presently, they are released in the Delta).
Population abundance and recruitment of white sturgeon are mainly a function of annual Central Valley hydrology (river flow), with abundant juvenile production occurring only in the wettest years. Past harvest has only involved a small percentage of the adult population, while watershed hydrology has orders of magnitude greater effect on recruitment and eventual adult population abundance.
Allowing a limited fishery could also help in continuing to assess the health of the population. Sport fishers should be asked to contribute important information on the sturgeon they catch.
This summer’s placement of the False River Barrier in the central Delta has been touted for saving reservoir storage during this fourth year of drought.
Contra Costa Times quoted DWR on the recent removal of the False River Barrier: “The state also managed to reduce the volume of fresh water it released from reservoirs to add to the Delta, preserving the resource instead for the times that salmon need infusions of colder water to survive.” (Contra Costa Times 10/2/15)
DWR also posted: “The barrier helped limit the tidal push of saltwater from San Francisco Bay into the central Delta and minimized the amount of fresh water that had to be released from upstream reservoirs to repel saltwater.”1
A DWR news release stated: “The barrier was an essential part of DWR’s strategy to maintain good water quality in the Delta and preserve water in upstream reservoirs to help keep young salmon cool enough to stay alive downstream of dams….The water users in the interior of the Delta, including many farmers and residents there, would have experienced much higher salinity without it…Monitoring at various stations in the Delta showed that the barrier indeed helped improve water quality in the central and south Delta.”2
Question 1. Did the False River Barrier save reservoir water by reducing release requirements?
A. Shasta – the answer is no, Shasta retained its prescribed releases all summer. There was thus no benefit of False River Barrier in retaining Shasta’s cold-water pool.
B. Trinity – no, it too contributed only to the fixed release to Sacramento River.
C. Oroville – releases to Feather River were relatively high much of the summer contributing substantially to Delta inflow.
D. Folsom – Releases to American River were relatively high all summer contributing substantially to Delta inflow, although depleting the reservoir’s overall storage and cold water pool.
E. New Melones – Stanislaus and San Joaquin flows were minimum all summer.
The overall answer is that slightly less Oroville and Folsom releases may have been needed with the False River Barrier; whether releases were lower or not is difficult to determine
Question 2. Was less freshwater outflow to the Bay required because of the False River Barrier?
No, outflow standards were prescribed by State Board and for the most part were met.
Question 3. Was less freshwater inflow needed to maintain the salinity standards at Threemile Slough, Jersey Point, and South Delta?
Threemile Slough was the controlling compliance point this summer, at times requiring increased Delta inflow and closure of the Delta Cross Channel for compliance. The False River Barrier likely increased the effectives of these measures to lower Threemile salinity.
Question 4. Did False River Barrier result in lower salinity in Central and South Delta?
No, salinities were higher than either 2013 or 2014.
Question 5. Was Franks Tract salinity lower because of the False River Barrier?
No, because salinity entered via the lower San Joaquin from San Andreas Landing via the mouth of Old River, as both these sites had higher salinity than in 2013 or 2014. The lower San Joaquin from Jersey Point to Prisoners Point thus suffered higher salinities in 2015 to meet South Delta export demands without False River inputs.
Question 7. Were South Delta exports higher than would have been possible without the False River Barrier?
Yes, because a higher proportion of freshwater inflow from the Sacramento River via the Delta Cross Channel and Georgiana Slough could be exported with False River closed.
Conclusion:
The Department of Water Resources’ assertion in the news article that salmon benefitted from the False River Barrier is unfounded. There were no measurable savings to reservoir storage or cold water pools essential to salmon.
Salinity found another path into Franks Tract via the mouth of Old River, but to the detriment of upstream movement of the Low Salinity Zone in the lower San Joaquin River. South Delta exports were able to take a higher portion of the freshwater inflow to the Delta from the Sacramento River because of the False River Barrier. Higher South Delta salinities in 2015 demonstrated a willingness to accept higher salinities in exports with the False River Barrier in place or simply an extreme demand for some summer export. Salinities dropped sharply in September with higher freshwater inflows (and outflows) to accommodate South Delta export and water transfers. The transfers were possible as water demands from the Sacramento Valley and Delta sharply declined, and water was sold for transfer south of the Delta. The False River Barrier likely helped facilitate the across-Delta transfers, which declined after the False River Barrier was removed at the end of September.
State Water Projects south Delta exports at Clifton Court Forebay summer 2015.
Central Valley Project south Delta exports at Tracy Pumping Plant summer 2015.
Environmental Factors Affecting Smoltification and Early Marine Survival of Anadromous Salmonids. 1980. GARY A. WEDEMEYER, RICHARD L. SAUNDERS, and W. CRAIG CLARKE1.
“There is reason to suspect that in many cases apparently healthy hatchery fish, though large and silvery, are not actually functional smolts and their limited contribution to the fishery, even when stocked into the same rivers from which their parents were taken, results from their being unprepared to go to sea. This failure to produce good quality smolts probably arises from an incomplete understanding of exactly what constitutes a smolt, as well as from a lack of understanding of the environmental influences that affect the parr-smolt transformation and which may lead, as a long term consequence, to reduced ocean survival.”
This paper is over thirty years old (1980), yet it still rings true. It is most certainly a complicated subject that is an on-going concern in hatchery science and management. There remains room for improvement if funding is available for hatchery program upgrades.
“In the absence of complicating factors such as altered river and estuarine ecology, smolt releases should be timed to coincide as nearly as possible with the historical seaward migration of naturally produced fish in the recipient stream, if genetic strains are similar. At headwater production sites, much earlier release may be called for… The desired result is that hatchery reared smolts which are genetically similar to wild smolts enter the sea at or near the same time.”
It has been apparent for many decades that Central Valley Fall Run and Spring Run Chinook have a classic “ocean-type” life-history pattern, wherein young spawned in the fall head to the ocean early in their first year rather than as yearlings. Even within the ocean-type, Central Valley Fall Run have two types: one has fry rearing in the estuary (Bay-Delta) and the other in rivers. Of these two types, Valley hatcheries have chosen to manage for the latter. Hatcheries pump out smolts by the millions in April and May, on top of a smaller number of “wild” river-smolts. I believe the “river-smolt” type has been the minority contributor at least since all the dams were built. There simply is not enough river habitat, and what there is has been severely degraded by dams, water management, and physical habitat damage (e.g., levees and land use). The majority contributor is the Bay-Delta or “estuary-smolt” type. Fry that move to the estuary in December-January grow quickly and enter the ocean as smolts in March, a month or more before the river-type. This is a huge advantage for the estuary-type. The hatchery programs could focus more effort on this type by out-planting fry to the estuary or lower river floodplains immediately above the estuary (e.g., Yolo Bypass). Experimental out-planting of hatchery fry to rice fields in the Yolo Bypass has proven promising2. There are also many natural habitats in the lower river floodplains and Bay-Delta that could accommodate out-planting.
This post is part of a 4 part series on hatchery reform, check back into the California Fisheries Blog over the next week for Parts 3 and 4.
