Lower American Water Temperature Threshold

Ecological Thresholds Queries
Clear Creek Lower American River Sacramento River Stanislaus River

This page provides analysis, based on Reclamation 2019 Proposed Action, of current and historical water temperature conditions for fish using only observed data. Actual pre-season and in-season management decision processes are complex employing multiple sources of observed data, models, and forecasts. For further information, see the Thresholds section.

Note: Years prior to 2019 pre-date the Reclamation Proposed Action and are provided for historical perspective on conditions.
Line chart for 2026 Lower American River daily average flow at Lake Natoma Nimbus Dam (NAT) and water temperatures, below Watt Ave Bridge (AWB), and at Fair Oaks (AFO). Water temperatures (in degrees Fahrenheit) and flow in cubic feet per second (CFS). Data retrieved from CDEC; figure generated by SacPAS.
2026 Water Temperature Threshold Analysis and Exceedance
Steelhead
Life Stage		 Life Stage
Dates		 Criterion Possible
Days		 Data
Days		 Missing
Data
Days		 Total Period Analyzed Criteria Exceedance
Average
Water
Temperature		 Days in
Threshold		 Days First Day Last Day
Juvenile Rearing 5/15-10/31 Below/Equal 65°F 0 0 0          
Juvenile Rearing (limited coldwater) 5/15-10/31 Below/Equal 68°F 0 0 0          
Spawning 11/1-12/31 Below/Equal 56°F 0 0 0          
graph Lower American Water Temperature Threshold Analysis History
2026 Lower American Water Temperature Threshold Analysis Data Table for American R blw Watt Ave Bridge (AWB)
Date Value Rearing
65°F
5/15-10/31		 Rearing (limited coldwater)
68°F
5/15-10/31		 Spawning
56°F
11/1-12/31
Date Value Rearing
65°F
5/15-10/31		 Rearing (limited coldwater)
68°F
5/15-10/31		 Spawning
56°F
11/1-12/31
2026-01-03 51.20      
2026-01-02 51.40      
2026-01-01 51.12      


Calendar Year 2026 Lower American River Flow and Water Temperature Data Table
Date Lake Natoma (Nimbus Dam) (NAT)
Reservoir Outflow (CFS)		 American R at Fair Oaks (AFO)
Water Temperature (°F)		 American R blw Watt Ave Bridge (AWB)
Water Temperature (°F)
2026-01-014808.4650.8951.12
2026-01-024992.6750.9351.40
2026-01-036736.6750.6651.20
2026-01-04   
2026-01-05   
2026-01-06   
2026-01-07   
2026-01-08   
2026-01-09   
2026-01-10   
2026-01-11   
2026-01-12   
2026-01-13   
2026-01-14   
2026-01-15   
2026-01-16   
2026-01-17   
2026-01-18   
2026-01-19   
2026-01-20   
2026-01-21   
2026-01-22   
2026-01-23   
2026-01-24   
2026-01-25   
2026-01-26   
2026-01-27   
2026-01-28   
2026-01-29   
2026-01-30   
2026-01-31   

Data Methods and Notes

Data Methods

  1. Data Courtesy of CDEC
  2. Hourly data for American R blw Watt Ave Bridge (AWB) is retrieved from CDEC on a daily basis.
  3. Columbia Basin Research (CBR) QA/QC process on AWB hourly data for outliers, false data (e.g., 32°F measured by satellite), and data outside expected range of observation (e.g., 90°F). Data loaded into CBR database.
  4. CBR calculates Daily Average values based on CBR cleaned hourly values.
  5. Query for daily average water temperature for selected year.
  6. Examine daily average data record for 65°F exceedance.
  7. Examine daily average data record for 68°F exceedance.

Threshold Analysis Criteria

Please refer to the American River Group (ARG) Annual Report of Activities for details on within water year activities.

Target analysis and exceedance found on this page is based on criteria as described in Reclamation 2019, p4-2.

Reclamation 2019. Reinitiation of Consultation on the Coordinated Long-Term Operation of the Central Valley Project and State Water Project Central Valley Project, California Mid-Pacific Region, Final Biological Assessment, Chapter 4: Proposed Action. October 21. Available online: https://www.usbr.gov/mp/bdo/lto/biop.html

May 15 through October 31 daily average water temperature of 65°F (or target temperature determined by temperature model) or lower at Watt Avenue Bridge. When the target temperature requirement cannot be met because of limited coldwater availability in Folsom Reservoir, then the target daily average water temperature at Watt Avenue may be increased incrementally (i.e., no more than 1°F every 12 hours) to as high as 68°F. November 1 through December 31 daily average water temperature of 56°F target if cold water pool allows. A temperature higher than 56°F may be targeted based on temperature modeling results.