Category Archives: Bay-Delta

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 ↩

2025 Sturgeon Moon

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The 2025 Sturgeon Moon (August 9 full moon) wreaked havoc on San Francisco Bay as it had in recent years1. The main effect was warm fresh water from the Delta draining into the Bay (Figure 1). The tidal effect of the super moon dropped water levels sharply about two weeks before the super moon (Figure 2). Warm water built up in the Bay over several days (Figure 3). A plankton bloom appeared in the North Bay soon thereafter (Figure 4). Is anyone checking on the sturgeon in the Bay? Will the coming heat waves over-heat the Bay?

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Figure 1. Fresh water drained into the Bay at Martinez for several days in late July, beginning about 14 days prior to the full moon.

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Figure 2. Water level of the Bay at Martinez July and early August 2025.

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Figure 3. Water temperatures increased at Martinez with the warm inputs from the Delta and Suisun Bay.

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Figure 4. Small plankton blooms appeared around the peripheries of San Pablo and Suisun bays and in Montezuma Slough at the end of July with the warm freshwater inputs. Source: https://www.cbr.washington.edu/sacramento/data/query_river_graph.html

 

California Salmon Recovery – Series Introduction

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This Introduction is the first in a series of posts that summarize elements of my recommended plan for Central Valley salmon recovery. Central Valley salmon runs over the recent five decades have varied from a total near 100,000 to near a million spawners with an average of 200-300 thousand (Figure 1). About 90% of the salmon runs have been fall-run. Spring-run and winter-run salmon have declined and are listed under the state and federal endangered species acts. All four runs are supported by hatcheries that raise about 30 million juveniles per year for release to rivers, the Bay-Delta, and the coastal ocean. Each of the run types are made up predominantly of hatchery-produced salmon. A few small stocks are comprised mainly of wild salmon, while most runs have a small “wild” or natural-born component. Rebuilding wild salmon stocks while providing for historic levels of commercial and recreational salmon harvest is the dual program mission.

The total number of adult salmon produced in the populations includes escapement to the spawning rivers described above as well as adult salmon harvested in the ocean, Bay-Delta, and rivers, prior to the spawning runs. These estimates are of the human harvest (Figure 2) and do not include harvest by marine animals or illegal fishing. Human harvest rates over the past four decades have been 50-70% on average except in years when the fishery is restricted (2008-2010 and 2023 and 2024) (Figure 2). Government agencies often restrict harvest when the Sacramento Fall Run Index falls to near a target minimum of 122,000, a condition commonly referred to as “overfished.”

The goal of my recovery plan is to return total adult salmon escapement to near a million fish, with a further harvest of 500,000 adult fish. The harvest would focus on hatchery fish, while habitat improvements would focus on rebuilding wild, genetically pure populations and their critical habitat.

The primary tools of the proposed recovery program include hatcheries, wild salmon sanctuaries, improvements in water project management and infrastructure, habitat enhancements, and changes to fishery management. Hatchery programs would include “production” hatcheries to produce marked smolts for release for harvest and maintaining spawning populations in rivers that cannot sustain wild populations. “Conservation” hatcheries would support the protection, maintenance, and development of “wild,” “genetically-pure” populations.

The actions I propose are not radical or new: they have been included in many plans and program recommendations for decades.  Many have been successfully implemented on a small scale in the Central Valley or in other large salmon watersheds of the Pacific Northwest and Alaska.

Figure 1. Total Central Valley Chinook salmon escapement by run type 1975-2023. (Source: Grandtab)

Figure 2. Sacramento River watershed salmon population index 1983-2023. Source: NOAA Fisheries and Pacific Fisheries Management Council. Note there was no harvest allowed in 2024, as in 2023.