This script constructs real-time winter-run redd dewatering estimates based on most recent data available from CDFW (September 05, 2024) for winter-run data and dewatering estimates from USFWS (2006; see citation). Data are also available in 2024 Winter-run Data file.xls online at calfish.org.
This document is also now available on SacPAS. However, data on the SacPAS webpage may not immediately reflect data in the document as updates to the webpage with newest flow and redd data may be pending.
Please note that all data are preliminary until data collection is finalized. Likewise, there are uncertainties with forecasts which may lead to changes in proposed operations.
As of August 21, 2024, the unexpanded redd count is 147 Winter-run redds. It is important to note that until data collection is completed for the year these are the minimum number of possible redds. The Winter-run number will always expand upon final analysis but gives an in-season guard rail of the minimum number of redds this year.
Given that the number of Winter-run redds is always larger than the early season carcass counts, an expansion number based on historic data is multiplied by the carcass count to estimate the total number of redds for the season before the end of the season’s final estimate is developed and the final redd count is known. Average 2005-2022 expansion was 1.98 * the total redd count, and thus we focus on an expansion factor of 2 to represent expected final redd count and support decision-making.
Name | Expansion Number | Total Redds | 1% |
---|---|---|---|
Current Count | 1 | 147 | 1.47 |
Anticipated Expansion | 2 | 294 | 2.94 |
As of September 05, 2024, 3 Winter-run redds have emerged and 0 have been dewatered. This leaves 14 shallow water redds of concern.
There is no real time data on fall-run redd counts. Estimates are predicted based on estimated dewatering percentages from USFWS (2006) and spring-run and fall-run spawn timing based on fresh female carcasses encountered by week from 2003 through 2022. Emergence timing were predicted from average water temperatures over the same time period. Fall-run dewatered redd estimates range from 6.5 to 13.3%. Note that fall-run dewatering estimates are likely overestimated using the dewatering percentages from USFWS (2006), and likely do not reflect actual dewatering percentages and should only be used for comparative purposes between scenarios. A comparative analysis between field and modeled dewatering percentages by Gosselin and Beer (2024) can be found here: https://www.cbr.washington.edu/sacramento/fishmodel/Note_on_Redd_Dewatering_Observed_v_Predicted.pdf.
An analysis on the relationship between winter-run chinook salmon temperature dependent mortality relationship and Shasta Reservoir end-of-year storage suggests a threshold of 2,200 TAF end of September Shasta Storage to assess the impacts of TDM impacts on next year’s cohort. Next year’s cohort is expected to experience minimal TDM impacts when end of September Shasta Storage is greater than this threshold, while values lower than 2,200 TAF are correlated with potentially more negative TDM impacts. As of August, End of September Shasta Storage is expected to be 2717 TAF.All proposed scenarios are anticipated to have EOS storage greater than the 2200 TAF threshold and therefore would not be expected to contribute to TDM impacts to winter-run chinook salmon in the subsequent year (see Table 2).
Metric | aug50wr1 | aug90 | aug90wradjdec | aug90wrdec | aug90wrflatdec | aug90wrshapedec |
---|---|---|---|---|---|---|
Avg Sept Flow (cfs) | 8369 | 8929 | 8053 | 8053 | 8269 | 8053 |
Avg Oct Flow (cfs) | 6000 | 6500 | 6871 | 7065 | 7500 | 7000 |
Sept-Feb Total Volume (TAF) | 2107 | 1910 | 1955 | 1926 | 1966 | 1922 |
Aug-Sept Total Volume (TAF) | 1213 | 1247 | 1195 | 1195 | 1208 | 1195 |
Anticipated EOS Storage (TAF) | 2684 | 2717 | 2665 | 2665 | 2678 | 2665 |
Winter-run Redds Dewatered | 0 | 2 | 0 | 0 | 0 | 0 |
Winter-run Percent Lost (current count) | 0 | 1.36 | 0 | 0 | 0 | 0 |
Winter-run Percent Lost (mean expansion of 2) | 0 | 0.68 | 0 | 0 | 0 | 0 |
Winter-run Redds Dewatered (250 cfs buffer) | 0 | 3 | 0 | 0 | 0 | 0 |
Winter-run Percent Lost (250 cfs buffer) | 0 | 2.04 | 0 | 0 | 0 | 0 |
Fall-run dewatered (%) | 6.7 | 6.5 | 13.3 | 10.4 | 11.1 | 9.7 |
Scenario | Description |
---|---|
Aug 90 (aug90) | Initial rough template scenario put together based on Aug 90% exceedance forecast. Strategy is to drop to baseflows as quickly as possible while meeting numerous downstream needs, reduce fall-run redd dewatering, conserve water for future years. Does not follow ramping rates |
Aug 50% WR1 (aug50wr1) | Draft scenario based off of August 50% forecast. Developed on 8-27-2024 to avoid any winter-run redd dewatering. |
Aug 90% WR dec (aug90wrdec) | Developed on 9/6/2024. Based on the 90% forecast exceedance. Follows ramping rates. Keswick releases decrease in late September and then increase as demand increases later in October. |
Aug 90% WR flat Dec (aug90wrflatdec) | Developed on 9/6/2024. Based on the 90% forecast exceedance. Follows ramping rates. Flows remain at 7,500 cfs in October. |
Aug 90% WR shape Dec (aug90wrshapedec) | Developed on 9/6/2024. Based on the 90% forecast exceedance. Follows ramping rates. Shifts 500cfs diversion from late Oct to early Oct. |
Aug 90% WR adj Dec (aug90wradjdec) | Developed on 9/6/2024. Based on the 90% forecast exceedance. Follows ramping rates. Keswick releases decrease in late September and then increase as demand increases later in October. Flows remain higher in early November to shift diversions later into the season. |
Gard, Mark. 2006. Relationships between flow fluctuations and redd dewatering and juvenile stranding for Chinook Salmon and Steelhead in the Sacramento River between Keswick Dam and Battle Creek. 94 pages.
Gosselin, J.L. and W.N. Beer. 2024. Sacramento River Winter-run Chinook Salmon Redd Dewatering: a Note on Comparing Observed and Predicted. Central Valley Prediction and Assessment of Salmon (SacPas; https://www.cbr.washington.edu/sacramento/). Columbia Basin Research, School of Aquatic and Fishery Sciences, University of Washington.