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