Category Archives: Bay-Delta

Bay-Delta Conditions – Early Spring 2026

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Figure 1. Sacramento River system and major water gaging locations in red.

Figure 1. Sacramento River system and major water gaging locations in red.

Dry and Warm Beginning in March

The end of winter 2026 brought dry conditions to the lower Sacramento River and Bay-Delta (Figure 1). What had been wet-year-type conditions in early March at Wilkins Slough (WLK) and Freeport (FPT), and high Delta outflows (DTO), had become dramatically drier by late March (Figures 2 and 3). The lower flows and dry warmer weather brought warm water temperatures stressful (>65ºF) to many of the Delta’s native juvenile fish (smelt, salmon, steelhead, and sturgeon) that concentrate in the lower Sacramento River and the Bay-Delta in early spring.

Reservoirs were holding back what remained of the winter snowmelt (Figure 4), putting unnecessary stress on this year’s fish reproduction. Minimum flows should have been 10,000 cfs at Wilkins Slough, 20,000 cfs at Freeport (below inputs from the Feather and American Rivers), and 10,000 cfs Delta outflow (see Figure 1 for locations).

Delta exports were moderate but falling from 8000 cfs to 5000 cfs during March (Figure 5). With falling Delta inflows and dry and warming conditions, central and southern Delta water temperatures also increased to stressful levels (reaching 70ºF, Figure 5). The moderate exports decreased outflow and increased Delta water temperatures.

Many of the naturally produced juvenile salmon had passed into the Delta by early March (Figure 6) and began showing up in Delta export salvage (Figure 7).  Millions of Sacramento River hatchery salmon were released in late March and began showing up in Delta export salvage facilities (Figure 8).  These fish also suffered from the low flows and related stress-level water temperatures.

Wet and Cool April

Wet and cool weather returned to the Central Valley in April.  Reclamation also released a flow pulse from Shasta Reservoir into the Sacramento River to help salmon migrations (Figure 9).  Benefits of the flow pulse came late to the problem but will likely provide benefits further into the spring.

Figure 2. Sacramento River daily average streamjlow and water temperatures, and Delta outflow to the Bayin early spring 2026. Orange, green, and blue lines are recommended minimum daily-average flows for Freeport, Wilkins Slough, and Delta outflow. Red line is the sress-level for water temperature at Wilkins Slough and Freeport for juvenile Delta native fish.

Figure 2. Sacramento River daily average streamjlow and water temperatures, and Delta outflow to the Bayin early spring 2026. Orange, green, and blue lines are recommended minimum daily-average flows for Freeport, Wilkins Slough, and Delta outflow. Red line is the sress-level for water temperature at Wilkins Slough and Freeport for juvenile Delta native fish.

Figure 3. Delta outflow and Sacramento River channel flow below rhe Delta Cross Channel (GES) along with west Delta water temperatures at Antioch (ANH), Rio Vista (RVB), and Emmaton (EMM) in early spring 2026.

Figure 3. Delta outflow and Sacramento River channel flow below rhe Delta Cross Channel (GES) along with west Delta water temperatures at Antioch (ANH), Rio Vista (RVB), and Emmaton (EMM) in early spring 2026.

Figure 4. Streamflow and water temperature from the lower Feather River at Gridley (GRL) and American River at Fair Oaks (AFO) in early spring 2026.

Figure 4. Streamflow and water temperature from the lower Feather River at Gridley (GRL) and American River at Fair Oaks (AFO) in early spring 2026.

Figure 5. Delta exports from state Harvey Banks and federal Tracy pumping plants, San Joaquin River Delta inflow at Mossdale, and water temperatures at the three locations in early spring 2026.

Figure 5. Delta exports from state Harvey Banks and federal Tracy pumping plants, San Joaquin River Delta inflow at Mossdale, and water temperatures at the three locations in early spring 2026.

Figure 6. Catch of juvenile salmon in Knights Landing screw trap along with river flow, water temperature, and turbidity from August 2025 to April 2026.

Figure 6. Catch of juvenile salmon in Knights Landing screw trap along with river flow, water temperature, and turbidity from August 2025 to April 2026.

Figure 7. Export rates and juvenile salmon daily salvage at south Delta export pumping planrs in winter and early spring 2026.

Figure 7. Export rates and juvenile salmon daily salvage at south Delta export pumping planrs in winter and early spring 2026.

Figure 8. Marked hatchery salmon Delta pumping plant salvage and export rates from November 2025 to April 2026. Also shown is net flow in south Delta Old and Middle River channels (OMR) near export facilities.

Figure 8. Marked hatchery salmon Delta pumping plant salvage and export rates from November 2025 to April 2026. Also shown is net flow in south Delta Old and Middle River channels (OMR) near export facilities.

Figure 9. Shasta/Keswick Dam release rates into the Sacramento River near Redding CA in late winter and early spring 2026. Also shown is daily average rate for previous 62 years.

Figure 9. Shasta/Keswick Dam release rates into the Sacramento River near Redding CA in late winter and early spring 2026. Also shown is daily average rate for previous 62 years.

Once again, Sturgeon overlooked in Spring 2026

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Water temperatures are reaching lethal levels (22oC) for the newly spawned sturgeon eggs and fry in the lower Sacramento River. To save this broodyear of sturgeon, resource managers must immediately increase flows in the lower Sacramento River. Right now, those flows are unusually low.

The San Francisco Bay-Delta watershed is home to two native sturgeon species: white sturgeon and green sturgeon. White sturgeon are popular among sport fishers in major rivers and the Bay-Delta. Green sturgeon are less common and are protected under state and federal endangered species laws, making their harvest illegal.

Both species migrate from the ocean or Bay into rivers to spawn—a behavior known as anadromy. Green sturgeon tend to spend more time in marine environments and travel further upstream to reproduce. White sturgeon are larger and sought after by anglers. Both types feed along river and bay bottoms, often attracted by bait that has a strong scent. The introduction of non-native clams has given sturgeon an abundant food source, potentially boosting their growth. However, they are sensitive to warm water and thrive best in cooler, saltier environments below 68°F (20°C).

Spawning poses significant challenges for sturgeon. They use stored energy in late winter and spring to reach clean, cool, fast-flowing rivers with deep, rocky bottoms where they lay sticky eggs. After several days, these eggs hatch. The young fry drift down to the Delta and Bay over about a month, feeding and growing along the way. Their survival depends on river conditions—low flow and warm water can be fatal in dry years. During wetter years, strong currents help them safely reach the Bay.

Once in the Bay, sturgeon can take 10 to 15 years to mature before returning upstream to spawn. Unlike salmon, sturgeon live long lives and can reproduce multiple times.

The frequency of wet years and the quality of Bay conditions both affect how many adult sturgeon persist in the population. Recently, recreational fishing has removed about 5–10% of adults annually. Droughts pose bigger risks—especially to white sturgeon—by warming Bay waters and encouraging algae blooms that deplete oxygen, sometimes causing mass die-offs during the summer.

Measures needed to support sustainable sturgeon populations amidst climate change include maintaining adequate river flows and suitable water temperatures in the Sacramento River, Delta, and Bay. This is especially important during spring and early-summer spawning and rearing periods.

Under current water management, most young sturgeon fail to survive the Delta due to poor flows, high temperatures, predation, and entrainment into water diversions. Summer is a critical season in the Bay, where most sturgeon reside, and healthy conditions are vital. Some years, large tides associated with Super Moons bring warm water into the Bay, triggering harmful algal blooms. Consistent freshwater inflow is necessary to support the food web and keep the Bay cool and oxygenated.

During consecutive dry years, population maintenance involves options like hatchery releases, rescuing stranded sturgeon, and stricter controls on fishing. The top priorities should be protecting breeding adults over 15 years old, ensuring adequate recruitment of younger subadults, and improving the survival of eggs and juveniles. Achieving these goals requires enhanced scientific monitoring and assessment of both the fish and their habitats, as is commonly recommended for other native fish like salmon and steelhead.

The current status of sturgeon is less well documented than other species like salmon, steelhead, smelt, and striped bass. Unlike others, there is no formal recovery plan for sturgeon. There are increasing calls to end the sport fishery and list white sturgeon as endangered. However, some scientists and resource managers argue that more pressing threats should be addressed first, and recommend focusing on gathering data from the fishery and data on population abundance.

In my last post on the sturgeon (February 2026), I hypothesized that the big reason for the unsuccessful sturgeon reproduction in water years 2024 and 2025 was poor conditions in the spring spawning and early rearing reach of the middle Sacramento River.  Water temperatures were above optimal (>65oF) and at times stressful (>68 oF) or even lethal (>72 oF) in spring 2024 and 2025.  Few juvenile sturgeon survive to reach the Delta under these habitat conditions.  This was one of the factors that led the State Water Board and USEPA to set 68 oF as the water quality standard for the Sacramento River two decades ago. This standard is also a condition of the State Water Board water right permits for the state and federal water projects.

Once again, during a relatively wet winter-spring, both the sturgeon and the water quality standard seem to be overlooked (see Figure 1).

To save this broodyear of sturgeon, resource managers must immediately increase flows in the lower Sacramento River. Right now, those flows are unusually low.

For more on white sturgeon science, monitoring, and fisheries management see https://wildlife.ca.gov/Conservation/Fishes/Sturgeon/White-Sturgeon.

Figure 1. Sacramento River streamflow and water temperature at Wilkins Slough in the lower prime spawning reach of white sturgeon in spring 2026.

Figure 1. Sacramento River streamflow and water temperature at Wilkins Slough in the lower prime spawning reach of white sturgeon in spring 2026.

Reclamation plans to take more water from the Delta

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A December 3, 2025 article in the LA Times warns of the federal government’s plan to take more water from the Delta. This is not something new – they have maximized exports much of this year and last year (Figure 1).  The State of California has also been doing this, but to a lesser extent (Figure 2).  Together, the two projects can export up to 22,000 acre-ft per day (8,000 acre-ft/day at Tracy, 14,000 acre-ft/day at Banks).  In a wet (2023) or above-normal year (2024 and 2025) exports can exceed 6-million acre-feet out of a potential maximum export pumping capacity of 8 million acre-feet.

The projects were able to exceed expectations in above-normal water year 2025 by eliminating the Fall-X2 Action that over the past decade required higher Delta outflows and lower exports in the September-October period to protect Delta smelt in the Bay-Delta.  In September 2025, the projects were able to export 674,000 acre-feet by dropping the Fall-X2 Action, compared to 536,000 acre-feet in September 2024 when the Fall-X2 Action was implemented.

The increased September exports in 2025 had significant environment effects that impacted salmon, smelt, and other Bay-Delta native fishes.

  • First, Delta outflow to the Bay was reduced in half (about 300,000 acre-feet, Figure 3) through a combination of the higher exports and lower reservoir releases (Delta inflow, Figure 4). That led to higher temperatures of water entering the Bay and the low salinity zone (LSZ) moving upstream from the Bay into the west Delta channel near Rio Vista (Figures 5 and 6).  These effects are detrimental to salmon at the peak of their fall migration into the Bay from the ocean and to the low salinity zone, which is designated critical habitat for smelt.
  • Second, lower Delta inflow from the Sacramento River (Figure 4) led to higher water temperatures in the north Delta at Rio Vista (Figure 6) and Freeport (Figure 7).
  • Third, reduced flows in the lower Sacramento River (Wilkins Slough, Figure 8) led to higher water temperatures (Figure 9), detrimental to salmon during their spawning migration to the upper Sacramento River and its tributaries.

In drier years (below-normal, dry, and critical), there are no Fall-X2 Actions, but there are many other restrictions on river flows, exports, and reservoir storage use to protect fish and their habitat as well as future water supplies.  In the past, Delta exports in drier years have been limited to only 3 to 5 million acre-feet per year.  We have yet to see the federal government’s plan to export more water in such years.  We can only guess as to what drastic changes to expect and the environmental damage that could ensue with the new federal export plan.  Higher spring exports in 2025 (see Figure 1) is one such change.

Figure 1. Federal exports from the south Delta via the Tracy Pumping Plant (TRP) in 2024 and 2025

Figure 2. State exports from the south Delta via the Harvey Banks Pumping Plant (HRO) in 2024 and 2025.

Figure 3. Delta Outflow to the Bay in Aug-Sept period of 2024 and 2025. The Fall-X2 Action was not implemented in September 2025.

Figure 4. Streamflow in the north Delta at the Freeport gage May-Dec 2024 and 2025. The Fall-X2 Action was implemented in September 2024 but not in September 2025 nor in October 2024 or 2025.

Figure 5. Salinity and water temperature in the west Delta near Rio Vista from August 2023 through September 2025 with emphasis on Sep-Oct period. Red lines denote water temperature (20C) above which there is significant stress on migrating adult fall-run salmon. The Fall-X2 Action was not implemented in October 2024 or September 2025.

Figure 6. Water temperature in the Sacramento River channel at the Rio Vista Bridge gage Aug-Sep 2024 and 2025. The Fall-X2 Action was not implemented in September 2025.

Figure 7. Water temperature in the Sacramento River channel at the Freeport gage in September 2024 and 2025. The Fall-X2 Action was not implemented in September 2025.

Figure 8. Streamflow in the lower Sacramento River at the Wilkins Slough gage in September of 2024 and 2025. The Fall-X2 Action was not implemented in September 2025.

Figure 9. Water temperature in the lower Sacramento River at the Wilkins Slough gage in September of 2024 and 2025. The Fall-X2 Action was not implemented in September 2025.

Prognosis for the 2026 Salmon Season

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Since the year 2000, Fall Run Salmon adult escapement (run total) to the Sacramento River system (mainstem and tributaries) dropped from a peak of 400,000-800,000 to 100,000 or less (Figure 1).  The lowest escapement, near 50,000 in 2009, occurred with the fishery closed.  More recently, escapement fell below 100,000 in 2017 and 2022, with the fishery open.  With the fishery closed in 2023 and 2024, escapement increased to near 150,000, allowing for a very limited recreational fishery in 2025.

The fishery harvests are about 50% of the fishable stock (or what could be available for escapement, see Figure 2).   A normal fishery would lead to escapements under 100,000 in recent years.  These escapement levels would likely lead the Pacific Fisheries Management Council and California Fish and Game Commission to restrict the fishery again in 2026.

However, the agencies may be inclined to allow a fishery with some restrictions based on positive trends in habitat conditions and the higher jack salmon numbers in the limited 2025 fishery.  Water years 2023 and 2024 were relatively wet, which often leads to good survival conditions, and is likely to lead to a projection of good salmon numbers available in 2026.

I am inclined to greater optimism for 2026, as I was in 2025,1 because of the likely higher numbers of salmon in the ocean and potentially returning to the rivers next year.  The various factors supporting my reasoning are summarized below:

  1. Jack numbers were up based on escapement surveys, agency test fisheries, and the limited 2025 fishery.
  2. Brood years 2023 and 2024, which will make up much of the fishable stock in 2026, likely had good survival and production in wet year 2023 and above-normal water years 2024 and 2025 (compared to dry years 2020-2022). Fishery impacts to these broodyears were also minimal in 2024 and 2025.
  3. Hatchery smolt production in 2023-2025 was also good, with some improvements over the 2020-2022 drought years. Hatchery smolts released to the rivers near the hatcheries likely had a much improved survival rate in 2023-2025 over that in the drought years, because of higher transport flows.  Millions of hatchery smolts trucked to Bay and coast pens for release also had improved survival compared to river releases.
  4. Fishery restrictions in 2023-2025 likely improved wild salmon spawning numbers, leading to good wild salmon recruitment in the three wetter years.
  5. A 2026 fishery would likely benefit from good overall broodyear 2023 and 2024 survival and production.
  6. My estimate of the fishable stock of broodyears 2022-2024 in the ocean is 400,000-800,000 two-to-four year-old salmon. Under a 50% harvest, escapement in 2026 would be 200,000-400,000 (likely somewhat less, as not all the fishable stock would spawn in 2026).  I support this hypothesis with a descriptive Spawner-Recruit model that I developed (Figure 3) that has reasonably predicted escapement in the past several years.

If the fishery remains restricted for a fourth year in a row, escapement could reach or exceed 500,000 adult salmon, a number far in excess of the management target escapement of 120,000-180,000.  Such a case would unnecessarily deprive commercial and recreational fisheries of the potential harvest of 200,000 or more adult salmon in the ocean and rivers in 2026.

I remain concerned with the potential adverse effects on wild salmon stocks from fishery harvest (Figure 4). Limiting wild salmon harvest by adjusting fishery timing and location, restricting catches to marked hatchery fish (mark-selective fishery rules), and improving spawning, rearing, and migrating habitat, could help address these issues.

I am also concerned with the poor returns (escapement) from the Coleman Hatchery’s in-river smolt releases that result in low fishery contributions, low escapement (Figure 5), and high rates of adult spawner straying to other spawning streams.  To address this problem agencies have considered higher smolt production, increased near-hatchery releases, trucking smolts to Bay-Delta-Coast, transporting eggs to Coleman from other hatcheries, hatchery fry releases to river floodplain and estuary habitats, reducing in-river predators, and improving migrating habitat during smolt releases.  All of these measures could help minimize the extent of this problem.

Figure 1. Note the very high escapement around the turn of the century. The improvement is attributable to the wet decade (1995-2005), increased hatchery production, trucking hatchery smolts to the Bay-Delta, and more protective management of fisheries and water supply. Subsequent poor escapement periods are generally attributed to multiyear drought impacts and over-fishing of drought-impacted salmon broodyears.

Figure 2. A 50% harvest rate is about what has occurred over the recent decade under normal fishery regulations.

Figure 3. This complicated semi-quantitative spawner-recruit model display attempts to show that a normal spawner-recruit relationship is overwhelmed by hatchery, harvest, and water-year hydrology effects on recruitment. I predict 2026 escapement (recruits) with a normal fishery will fall into the green box (200,000-400,000) because 2023 and 2024 were wetter (blue) water years. Without a fishery, escapement would be near or above 500,000, a number well above the target escapement.

Figure 4. These spawner estimates for the upper Sacramento River represent the natural spawning escapement of the mainstem Sacramento River. The decline in this escapement component is considered a key factor in the overall decline of the Sacramento River fall-run salmon population. The decline is generally attributed to increasingly poor habitat conditions (water flows and temperature, pollution, predation, and water diversions) and over-harvest of wild or natural-born fish in the fishery.

Figure 5. Adult fall-run salmon returns to the Coleman Hatchery in the upper Sacramento River have been below 10,000 for several years. Preliminary estimates for 2025 indicate sharply higher returns to the Coleman Hatchery (near 40,000 or higher), the result of good hatchery smolt survival, no fishery for three years, and good river conditions this summer and fall.

The Fall-X2 Action – Benefits and Costs

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The 2008 Delta Smelt Biological Opinion for Central Valley Project (CVP) and State Water Project (SWP) operations included the Fall X2 Action to protect Delta smelt. The about-to-be implemented “Action 5” that will modify the 2024 biological opinions for the CVP and SWP will eliminate the Fall X2 Action entirely.

The Fall X2 Action required the CVP and SWP to keep brackish water west of the Delta in September and October in wet and above normal water years. The X2 location is defined as the location where salinity is 2 parts per thousand.1 X2 is located within what is known as the low salinity zone (LSZ, 1-6 parts per thousand).

Delta smelt and longfin smelt concentrate in the LSZ near X2 in summer and fall. Keeping X2 at Chipps Island (KM 71 from the Golden Gate, Figure 1) benefits the populations of Delta smelt and longfin smelt. Less effective options for the Fall X2 Action that require less Delta outflow have included other locations as far east as KM 80.

If freshwater outflow from the Delta is too low (at or below about 6000 cfs), the LSZ is located within the narrow channels of the west Delta. Water in the west Delta tends to be warmer and less productive than water in Suisun Bay. It is also more likely to be pulled south by pumping at the CVP and SWP’s south Delta export facilities.
The higher freshwater inflows needed for the Fall X2 Action also benefit other native fishes in the lower Sacramento River, its tributaries, and the Delta.

Harm comes to Bay-Delta fish in the form of high water temperatures and reduced food concentrations. When water temperatures climb into the range of 70-72°F, native fishes, including smelt, sturgeon, steelhead, and salmon, generally suffer stress-related poor growth and survival.

Warm Delta water blocks or hinders adult salmon in their upstream spawning migrations. (A water temperature of 72°F is the salmon avoidance temperature.) Adult salmon will hold in the Bay because of warm water temperatures, resulting in delayed spawning and the expenditure of the critical energy needed for spawning. Warm rivers cause further delay, diseases, and thiamine deficiency, reducing the ability of salmon to spawn successfully. Higher water temperatures (> 65°F) during spawning migrations also lead to reduced salmon egg and embryo survival. High water temperatures in juvenile rearing habitat and emigration routes lower the growth and survival of juvenile salmon, steelhead, smelt, and sturgeon, and increase predation on all these species.
In the Delta specifically, high water temperatures in the Delta block emigration of juvenile salmon and reduce growth rates and survival of juvenile salmon and smelt. Both salmon and smelt species are highly sensitive to warm and varying water temperatures. Heat transfer and retention during high air temperatures from late-spring to early-fall is greater at lower flows.

In summary, water temperatures above 72°F are highly stressful on native Bay-Delta fishes, often leading to poor growth, low-oxygen stress, more disease, greater susceptibility to predation, and competition from non-native fish, all of which lead to reduced survival. Also, many non-native fish such as largemouth bass thrive in higher water temperatures (72- 80°F).

The Fall X2 Action
The Fall X2 Action focuses on increasing Delta inflow and outflow in the months of September and October when seasonal flows are naturally lower and irrigation demands less, while air temperatures remain high. Late summer and early fall are a key period in the life cycle and overall reproductive success of many Bay-Delta native fishes.

Bay-Delta
The Fall X2 Action is needed to maintain low salinity and water temperature in the optimal range of native Bay-Delta fish. In the 2017-2019 period, with two wet years and one below-normal year, the higher prescribed Delta outflow (DTO) of the Fall X2 Action (Figure 2) in the wet years kept the Bay fresher (Figure 3) and Delta outflows cooler (Figures 4 and 5). In the two above-normal years of 2024 and 2025, the lack of a Fall X2 Action in September 2025 (Figure 6) led to high September water temperatures in the western Delta (Figure 7). The lack of Fall X2 Action in October 2024 (Figure 6) contributed to stressful (>65º F) October water temperatures at Rio Vista bridge in the west Delta (Figure 7). 2020, a below normal water year, provides another example of high September-October water temperatures when the Fall X2 Action was not implemented (Figure 8).

Lower Rivers
The Fall X2 Action requires roughly 5000 cfs of extra Delta inflow for two months (assuming needed flow is not provided by foregone river diversions or Delta exports). Releases from Shasta, Oroville, and/or Folsom reservoirs generally provide this inflow. That amounts to roughly 10,000 acre-feet of water per day, or 600,000 acre-feet for the full September-October period. In recent wetter water years, the CVP and SWP have offset some (or all) of this water cost by reducing reservoir releases in the summer and not meeting water quality standards for water temperatures in the lower Sacramento River. Flows in the lower Sacramento River at Wilkins Slough have been near 5000 cfs, when it takes about 10,000 cfs to maintain the 68º F standard.

The Cost
In summary, the amount of fresh water required to keep X2 in Suisun Bay in late summer and early fall of above-normal and wet water years requires approximately 600,000 acre-feet of stored project water or forgone diversions from rivers and exports from the Delta. That amounts to about 5% of total CVP and SWP storage capacity. It is also about 5% of the total annual upstream, in-Delta, and Delta export water use in the Bay-Delta watershed.

The about-to-be implemented “Action 5” that will modify the 2024 biological opinions for the CVP and SWP will eliminate the Fall X2 Action, and this water cost, entirely.

Figure 1. Bay-Delta and key water accounting and water quality locations.

Figure 2. Daily average Delta outflow (cfs) in September-October of water years 2017-2019. Fall X2 Action was implemented in wet year 2017 and 2019.

Figure 3. Salinity (EC) of east Bay near Chipps Island at Mallard Slough 2017-2019.

Figure 4. Water temperature in west Delta at Emmaton in September-October 2017-2019.

Figure 5. Water temperature in west Delta at Rio Vista in September-October 2017-2019.

Figure 6. Daily average Delta outflow (cfs) in September-October of above-normal water years 2024 and 2025. Fall X2 Action was implemented in September of 2024 and October of 2025.

Figure 7. Water temperature in west Delta at Emmaton and Rio Vista in September-October 2024 and 2025.

Figure 8. Daily average Delta outflow (cfs), Freeport river flow, and Emmaton and Rio Vista water temperature in July-October of water year 2020. The Fall X2 Action was not implemented in below-normal water year 2020.

  1. Also measured as about 3000 EC.  See https://pubs.usgs.gov/sir/2014/5041/pdf/sir2014-5041.pdf ↩