Did the Harvest Moon bring in the fall Chinook salmon run?

Posted on October 14, 2026 by Tom Cannon

In a September 26, 2026 post, I speculated on whether the 9/26 Harvest Moon tides might bring in a long-awaited late-summer salmon run to San Francisco Bay from the ocean. The late summer fishery catch was still going strong outside the Golden Gate in coastal waters, but numbers in the Bay, Delta, and rivers remained modest at best. My hunch was that the spring tides at the end of September would bring cooler water into the Bay, and the rivers would cool the Delta.

The late September spring tides and cooler air temperatures did provide a cooldown in the Delta (Figure 1), the west Bay (Figures 2 and 3), and the east Bay (Figure 4). However, the cooling period was short lived, as an early October heat wave brought back the warm water and stressful salmon migration conditions. Water temperatures remained above the optimal level for migration (at or below 18^oC/65^oF), and reached into the 68-70^oF stressful range in the east Bay and Delta (72^oF is the avoidance level). Ocean temperatures entering the Gate in early October were about 60-61^oF (above normal due to El Niño conditions); water exiting the Gate on the ebb was about 63-64^oF.

In the rivers upstream of the Delta, water temperatures also increased in early October. Shasta Dam releases lost access to the lake’s deep cold-water pool (Figure 5). The lower Sacramento River at the Wilkins Slough gage upstream of the Delta, at Freeport entering the north Delta, and at Rio Vista Bridge exiting the Delta warmed to 68-69^oF with the heat wave and dropping streamflows (Figure 6).

In 2026, there were changes in the biological opinions and incidental take permits for the Central Valley Project and State Water Project. These changes meant there were no Fall-X2 Delta outflows (greater than 10,000 cfs) that had been required in previous wet and above normal water years. Without Fall-X2 flows (Figure 7) Bay, Delta, and river water temperatures increased.

A week or more of cool weather beginning October 11 may yet open the window for the fall salmon run. It may also be a godsend for the million or more wild juvenile winter-run salmon produced this year on their late-fall downstream journey from the upper Sacramento River to the Delta.

Figure 1. Water and air temperatures September1 to October 7, 2026 in the lower Sacramento River channel of the Delta. FPT=Freeport, RVB=Rio Vista, EMM=Emmaton.

Figure 2. Near bottom salinity (EC) and water temperature (C) in western San Francisco Bay at the Richmond Bridge September 15 – October 8, 2026.

Figure 3. Near surface salinity (EC) and water temperature (C) in western San Francisco Bay at the Richmond Bridge September 15 – October 8, 2026.

Figure 4. Salinity (EC) and water temperature (C) in eastern San Francisco Bay at the Benicia Bridge September 14 – October 8, 2026.

Figure 5. Water temperature in the 30-mile salmon spawning reach below Shasta Lake in the upper Sacramento River below Keswick (rm 300), above the mouth of Clear Creek (rm 290), and at Balls Ferry (rm 276) May-September 2026. The water quality standard for the upper 60 miles below Keswick Dam is 56°F year round to protect spawning salmon.

Figure 6. Lower Sacramento River streamflow and water temperature at Wilkins Slough (rm 120) and Freeport (rm 46), and water temperature at Rio Vista Bridge (approx. rm 20) September 1 to October 6, 2026.

Figure 7. Estimated daily-average streamflow at Pittsburg in eastern San Francisco Bay in September 2026.

Will Harvest Moon bring in this year’s big salmon run?

Posted on September 26, 2026 by Tom Cannon

Will the Harvest Moon (9/26) with its spring tides (Figure 1) and cooler air and water temperatures (Figures 2 and 3) bring in this year’s expected big salmon run to the San Francisco Bay-Delta Estuary? Will East Bay Municipal Utility District (EBMUD) release fall salmon water pulses from Camanche Dam on the Mokelumne River beginning at the end of September, and if so, will they help attract the salmon as in prior years?

All the factors look good except for possibly one. Like last year, Reclamation is not implementing the Fall X2 provision of the 2019 Delta Smelt Biological Opinion – a provision that prescribes Delta outflows near 10,000 cfs in September of above-normal and wet years. Water years 2024-2026 were above-normal water years. Fall X2 September outflows were only provided in 2024 (Figure 4). Instead, September 2025 and 2026 Delta outflows were about 5,000 cfs, only slightly higher than drought year 2021 and 2022 September outflows.

Whether September Delta outflows are an important factor in the timing of the fall-Chinook salmon run into and through the Bay is a topic subject to further review.

Figure 1. Predicted tide height near the Golden Gate at NOAA gage #9414290 in September 2026. Source: NOAA.

Figure 2. Water and air temperatures July-September 2026 in the lower Sacramento River channel of the Delta. FPT=Freeport, RVB=Rio Vista, EMM=Emmaton.

Figure 3. Water temperature and ECnear the channel bottom at Benecia Bridge USGS gage near west Suisun Bay and Carquinez Strait September 14-20, 2026. Note colder higher salinity water incoming beginning on 9/17. Source: USGS.

Figure 4. Delta outflow (daily average) in summer 2021, 2022, and 2024-2026, with average for years 1990-1999

The Water Temperature of the Bay-Delta is Currently Unsuitable for Delta Smelt in Summer

Posted on August 13, 2026 by Tom Cannon

The last significant brood year reproduction of Delta Smelt occurred in 2011 (Figure 1a and 1b). The last significant brood years occurred from 2010-2012, and the population then collapsed during the 2013-2015 drought. The Delta is too warm in summer to allow a Delta Smelt recovery.

The demise of the Delta Smelt started in the late 1990s and accelerated from 2005-2006, above-normal and wet years that had unusually warm western Delta water temperatures in the prime Delta Smelt low-salinity-zone rearing habitat. The 2005-2026 decline of Delta Smelt and other pelagic Delta species was termed the Pelagic Organism Decline (POD).¹ The POD was studied for two decades, with multiple factors considered, including warming of the Delta as it relates to increasing Delta water exports and the associated lower Delta outflow.

After two decades of new environmental data available for the Delta, it looks more and more like increased water temperature was the main culprit in the demise of Delta Smelt. One of the best sources of long-term water temperature data is the gage at Emmaton in the western Delta, near the confluence of the Sacramento River and San Joaquin River channels at the entrance to San Francisco Bay in east Suisun Bay (see map, Figure 14). Water temperatures in early summer in wetter years 2005-2006 were higher than average and into the 73-75^oF lethal range for Delta Smelt (Figures 2 and 3). Similar warm temperatures were recorded at the Collinsville gage in east Suisun Bay in summer 2005 and 2006 (Figures 4 and 5). The western Delta and eastern Suisun Bay are the prime early-summer low-salinity-zone habitat of Delta Smelt.

The warmer summer trend in the western Delta continued after 2010-2012, the last Delta Smelt recovery years (Figures 6-9). Water temperatures were also high in summer in west Suisun Bay in many recent years (Figure 10).

Causes

Generally, the blame goes to Climate Change (i.e., Global Warming, El Niños, etc.) that cause droughts and warmer air temperatures. It is difficult to put blame on any one factor, especially when the potential factors are highly variable, often not controllable, or not always measured.

However, for Delta Smelt that usually live only one year, it is useful to look for causes in sudden drops in population indices or periods of declines (like droughts). I have analyzed many of these factors and trends, and I often come back to July (early summer) when juvenile Delta Smelt are usually settled into the low salinity zone in the western Delta and Suisun Bay. If that key habitat area gets too warm, then it only takes a few days to kill-off most of the population.

For this reason, I tend to focus on POD years 2005 and 2006 as a prime factor in the demise of Delta Smelt. As shown in Figure 3, July water temperatures reached lethal levels during the POD years; they had been at non-lethal levels in most years of the 1990s. A major change was that south Delta exports under Water Rights Decision 1641 (after 1999) were greater than occurred during the 1990s (Figure 11, Table 1). July exports were about 25% greater during the POD years, because D-1641 allowed higher exports (Figure 12). West Delta water temperatures were particularly high in the summer of water year 2005 (Figure 13). The combination of high early- summer (June-July) exports (Table 1) and high July water temperatures was a likely contributing factor to the post-2002 Delta Smelt summer and fall indices.

Table 1. June and July monthly-average exports in 2005. Pre-1995 exports limits are shown.

Month	June	July
Export Rate CFS	10,100	11,900
Pre-1995 Max CFS	6,000	9,000

After the 2010-2012 period in which the Delta Smelt population showed some recovery, the population collapsed to near zero. That decline was likely related to the persistent lethal water temperatures in summer in the western Delta and east Suisun Bay. There is ample evidence of warmer summers under the temporary urgency change petitions and orders in the two most recent multiyear droughts (2013-2015; 2020-2022).²

In summary, it is extremely difficult for the Delta Smelt population to recover in the Bay-Delta Estuary under current water management and environmental conditions, because water temperatures are too high in summer. Surely it remains possible to affect change with more progressive water management, but the capacity to affect change diminishes

Figure 1a. Delta Smelt Summer Townet Survey Index 1959-2023. Source: CDFW

Figure 1b. Delta Smelt Fall Trawl Survey Index 1967-2014. Source: CDFW.

Figure 2. Summer water temperature at Emmaton gage near the confluence of the Bay and Delta from 2000 to 2015. See map (Figure 14) for gage location.

Figure 3. Average daily water temperature is shown for July of years 2003-2006 at Emmaton in the western Delta. Also shown is the average water temperature at Emmaton for the same dates for years 1990-1999. The red line is the level above which water temperature is considered highly stressful or lethal to Delta Smelt with long-term exposure.

Figure 4. Water temperature (recorded hourly) at Collinsville gage in eastern Suisun Bay in 2005. Stress and lethal levels on Delta Smelt shown in colors.

Figure 5. Water temperature (recorded hourly) at Collinsville gage in eastern Suisun Bay in 2006. Stress and lethal levels on Delta Smelt shown in colors.

Figure 6. Water temperature and salinity (recorded hourly) at the Jersey Point gage in the west Delta channel of the San Joaquin River 2010-2016. Stress and lethal water temperature levels on Delta Smelt shown in colors. Note the higher summer water temperatures in drought years 2013-2015 and below-normal year 2016, as compared to the 2010-2012 recovery period.

Figure 7. Water temperature and salinity (recorded hourly) at the Rio Vista Bridge gage in the west Delta channel of the Sacramento River from 2010-2019. Stress and lethal water temperature levels on Delta Smelt are shown in colors. Note the higher summer water temperatures in drought years 2013-2015 and below-normal years 2016 and 2018, and wet years 2017 and 2019 than in the 2010-2012 recovery period.

Figure 8. July water temperatures at Antioch gage in western Delta San Joaquin River channel in six normal and wet years including 2010. Note red dotted line of 73ºF above which water temperature is known to be lethal to Delta Smelt in long-term exposure. Note lower water temperatures in 2010, a Delta Smelt recovery year.

Figure 9. July water temperatures at Antioch gage in western Delta San Joaquin River channel in five normal and wet years including 2011, a Delta Smelt recovery year. Note red dotted line of 73ºF above which water temperature is known to be lethal to Delta Smelt.

Figure 10. Water temperature (recorded hourly) at the Grizzly Bay gage in the west Suisun Bay 2018-2025. Stress and lethal water temperature levels on Delta Smelt shown in colors. Note the high summer water temperatures in these years except for wet year 2023 and above-normal year 2025.

Figure 11. Annual south Delta exports and running average trend line for years 1970-2025.

Figure 12. Maximum exports allowed under D-1641 (11,400 cfs) occurred in July 1999. The state Banks Plant (HRO) maximum rate is approximately 7000 cfs. The federal Tracy Plant (TRP) maximum rate is about 4400 cfs. Prior to 1995 the maximum south-Delta export rate was 9000 cfs under D-1485.

Figure 13. Summer water temperatures at Antioch and Emmaton gages in western Delta in above-normal water year 2005. Note red line at 73F above which is known to be lethal to Delta Smelt.

Figure 14. Map of the northern Delta and eastern San Francisco Bay (Suisun Bay)

The Premeditated Murder of Sacramento River Salmon in Summer 2026

Posted on August 11, 2026 by Tom Cannon

The Bureau of Reclamation is systematically emptying Shasta Reservoir of its cold-water-pool reserve this summer. At the current and planned rate of release, Sacramento River winter-run, spring-run, and fall-run salmon broodyears 2026 will not survive the summer and fall.

The process employed by Reclamation is premeditated murder of salmon in response to the Presidential Executive Order 14181. That order requires federal agencies to “override existing activities that unduly burden efforts to maximize water deliveries.”

Reclamation’s 2026 Sacramento River Temperature Management Plan (TMP) already contained information that showed Reclamation’s predicted water temperatures for end-of-summer Shasta Reservoir releases to be wildly optimistic. Table 2 of the TMP showed a planned June-August release from Shasta Reservoir of 1.9 million acre-feet. 2 million acre-feet was the amount of cold water in Shasta Reservoir on June 1 (Figure 1 below: black line within second-darkest blue).

Reclamation knew that that the cold-water supply in Shasta was already compromised by poor snowmelt and runoff. Nonetheless, Reclamation released the draft TMP in May. Reclamation ignored concerns from state and federal resource agencies, and proceeded to finalize and implement the TMP. Reclamation knew, or at the very least should have known, that it could not maintain 53.5ºF at the Clear Creek gage (CCR) and 56ºF at the Balls Ferry gage (BSF) even through August, let alone through September or October, with the planned level of releases from Shasta Reservoir for irrigation deliveries.

Can salmon be saved in 2026?

The CSPA 2021 TMP proposed a 5000 cfs release of 53-54ºF water from Keswick Reservoir, with no Trinity transfer through the Spring Creek Powerhouse, and with minimal daily peaking power production to limit withdrawals of warm water from the surface of Shasta Reservoir. The approximate 10,000 acre-feet/day CSPA proposed in 2021 is roughly the amount of cool (<52F) water left in Shasta Reservoir on August 1, 2026. That release schedule would sustain relatively cool water in the Sacramento River through October (Figures 1 and 2). This regime would maintain 54.5ºF at SAC and 56ºF at Clear Creek CCR at the control points through October. Though far from optimal, this would provide some minimal level of survival of broodyear-2026 salmon and provide an end-of-September Shasta storage level near 2.4 million acre-feet, as recommended by the State Water Board.

Figure 1. Shasta Reservoir’s daily isothermobaths (volume of storage) in 2026. Note Reclamation’s TMP EOS 2.2 MAF forecast. Source: sactemprpt-2.pdf.

Figure 2. Shasta Lake storage (acre-ft) in drought years 2015 and 2022, below normal 2020, and above normal 2026.

Reclamation Is Not Meeting the 2026 Shasta Temperature Management Plan

Posted on July 30, 2026 by Tom Cannon

The US Bureau of Reclamation is well on its way to failing to adhere to its 2026 Sacramento River Temperature Management Plan (TMP). The cold-water pool supply in Shasta Reservoir has fallen as low on this date in 2026 as it was in critical drought years 2015 and 2022 (Figure 1). Survival of winter-run Chinook salmon in the Sacramento River from brood years 2015 and 2022 was less than 5 percent because the cold-water-pool supply in Shasta Lake was exhausted before the end of summer. Reclamation is again creating similar conditions that threaten this year’s production onf winter-run and fall-run Chinook salmon in the upper Sacramento River below Shasta Reservoir.

The 2026 TMP proposed relaxing the requirements for salmon under the National Marine Fisheries Service’s (NMFS) 2024 LTO Biological Opinion for the Long-Term Operation (LTO) of the Central Valley Project and the State Water Project. Reclamation implemented TMPs under the LTO Biological Opinion in 2024 and 2025. 2024 and 2025 were similar water years that, like 2026, had above-average April storage in Shasta Reservoir. Part of Reclamation’s stated rationale is that 2026 had a low snowpack and thus a smaller cold-water pool in Shasta Reservoir.

Reclamation moved ahead with the 2026 TMP despite not receiving the approval of the State Water Board. The conflict with the Board is mainly over the target end-of-September (EOS) storage in Shasta Reservoir, with Reclamation planning for a 2.2 million acre-feet (MAF). The “Shasta Framework” in the LTO Biological Opinion calls for EOS Shasta storage of 2.4 MAF.

Also at issue is Reclamation’s ability to fulfill the TMP’s commitment to maintain a water temperature of 53.5°F at the Clear Creek gage near Redding through October 31 to protect salmon reproduction. Reclamation has achieved that temperature through July. A cooler than normal spring helped sustain the cold-water-pool supply. However, Reclamation is rapidly using up the cold-water pool by meeting high contractor water demands, by using cold water from Shasta to offset the import of warm Trinity-Whiskeytown water (about 15-20% of total Keswick Dam releases to the upper Sacramento River), and by maximizing peaking-power production at Shasta Dam.

Keswick Dam releases in July are a steady 13,000 cfs, providing approximately 6,000 cfs of contractor demands and 7,000 cfs flows and 68°F target water temperatures in the lower Sacramento River (at Wilkins Slough gage above the mouth of Feather River). At that rate, EOS Shasta storage of even 2.2 MAF will be difficult to achieve without exceeding agreed-to water temperature conditions. Reclamation will prematurely exhaust Shasta’s cold-water pool (Figure 1). Target water temperatures in the lower Sacramento River will be exceeded, as in past years.

Comparison of 2026 with Water Years 2024 and 2025, and Drought Year 2022

At the beginning of spring 2026, there was less snowmelt and a smaller cold-water-pool volume in Shasta Reservoir than there had been in 2024 and 2025 (Figure 2). The spring cold-water-pool conservation period was warmer, but the cold-water release target nevertheless started promptly on May 15. It will continue through October 31, unless the cold-water pool is depleted in September or October, as occurred in 2024.

Reclamation’s 2026 TMP is comparable to water year 2020 TMP, a dry water year (Figure 3). In 2020, the EOS storage was close to the 2.2 MAF target, but Reclamation failed to preserve the cold-water pool. Beginning in September and lasting through November, Reclamation released water from Keswick Dam that exceeded the temperature target in the 2020 TMP. The failure to sustain the cold-water supply increased mortality during the spawning and early incubation season of the winter-run salmon (September-October) and fall-run salmon (October-November).

Summary

In 2026, Reclamation must at minimum immediately revise its TMP to include the following criteria:

Reclamation must revise its present plan for contractor water deliveries. Otherwise, Reclamation will not meet temperature requirements to protect the salmon through the end of the irrigation season and beyond. Reclamation will have to reduce water deliveries to the 2020 levels or less to save the cold-water-pool supply and meet temperature criteria (Figure 4). The cold-water-pool supply in late July is at the drought year 2015 and 2022 level (see Figure 1), yet the Shasta Dam cold-water release is triple the 2022 level and double the 2015 level (Figure 5).
Reclamation must maintain water temperatures at a maximum of 53.5°F and 56°F at the Clear Creek and Balls Ferry gages, respectively, through October.
Reclamation must maintain maximum water temperatures of 68oF at the Wilkins Slough gage in the lower Sacramento River.
Reclamation must meet a target Shasta Reservoir EOS storage of 2.4 MAF.