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.