Lower American Water Temperature Threshold

Ecological Thresholds Queries

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.

line plot water temperature and flow — 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.

line plot water temperature and flow with temperature thresholds for fish life stages — Line chart for 2026 Lower American River daily average flow and water temperatures below Watt Ave Bridge (AWB). Threshold lines for Juvenile Rearing at 65°F, Juvenile Rearing (limited coldwater) at 68°F, and Spawning at 56°F. Water temperature (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
Steelhead Life Stage	Life Stage Dates	Criterion	Possible Days	Data Days	Missing Data Days	Average Water Temperature	Days in Threshold	Days	First Day	Last Day
Juvenile Rearing	5/15-10/31	Below/Equal 65°F	170	84	0	64.0°F	54	30	06/04	08/04
Juvenile Rearing (limited coldwater)	5/15-10/31	Below/Equal 68°F	170	84	0	64.0°F	79	5	07/22	08/03
Spawning	11/1-12/31	Below/Equal 56°F	0	0	0

line plot Lower American Water Temperature Threshold Analysis historical years

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
2026-08-06	62.65	Below	Below
2026-08-05	62.70	Below	Below
2026-08-04	65.63	Above	Below
2026-08-03	68.21	Above	Above
2026-08-02	67.69	Above	Below
2026-08-01	67.66	Above	Below
2026-07-31	67.04	Above	Below
2026-07-30	66.94	Above	Below
2026-07-29	67.54	Above	Below
2026-07-28	68.09	Above	Above
2026-07-27	68.29	Above	Above
2026-07-26	68.07	Above	Above
2026-07-25	67.49	Above	Below
2026-07-24	67.06	Above	Below
2026-07-23	67.07	Above	Below
2026-07-22	68.07	Above	Above
2026-07-21	67.93	Above	Below
2026-07-20	67.28	Above	Below
2026-07-19	66.92	Above	Below
2026-07-18	66.62	Above	Below
2026-07-17	65.92	Above	Below
2026-07-16	65.62	Above	Below
2026-07-15	65.85	Above	Below
2026-07-14	65.90	Above	Below
2026-07-13	64.50	Below	Below
2026-07-12	64.78	Below	Below
2026-07-11	65.29	Above	Below
2026-07-10	65.32	Above	Below
2026-07-09	64.93	Below	Below
2026-07-08	64.46	Below	Below
2026-07-07	64.24	Below	Below
2026-07-06	64.18	Below	Below
2026-07-05	64.01	Below	Below
2026-07-04	64.08	Below	Below
2026-07-03	63.69	Below	Below
2026-07-02	63.26	Below	Below
2026-07-01	63.21	Below	Below
2026-06-30	63.75	Below	Below
2026-06-29	64.24	Below	Below
2026-06-28	62.86	Below	Below
2026-06-27	62.10	Below	Below
2026-06-26	61.68	Below	Below
2026-06-25	61.92	Below	Below
2026-06-24	61.82	Below	Below
2026-06-23	61.66	Below	Below
2026-06-22	61.92	Below	Below
2026-06-21	62.01	Below	Below
2026-06-20	62.07	Below	Below
2026-06-19	62.41	Below	Below
2026-06-18	63.50	Below	Below
2026-06-17	63.88	Below	Below
2026-06-16	64.39	Below	Below
2026-06-15	64.83	Below	Below
2026-06-14	64.46	Below	Below
2026-06-13	64.70	Below	Below
2026-06-12	65.24	Above	Below
2026-06-11	66.79	Above	Below
2026-06-10	66.51	Above	Below
2026-06-09	65.45	Above	Below
2026-06-08	64.87	Below	Below
2026-06-07	64.14	Below	Below
2026-06-06	64.74	Below	Below
2026-06-05	66.22	Above	Below
2026-06-04	65.57	Above	Below
2026-06-03	63.79	Below	Below
2026-06-02	62.61	Below	Below
2026-06-01	62.09	Below	Below
2026-05-31	61.68	Below	Below
2026-05-30	60.72	Below	Below
2026-05-29	59.81	Below	Below
2026-05-28	59.99	Below	Below
2026-05-27	60.46	Below	Below
2026-05-26	59.64	Below	Below
2026-05-25	60.78	Below	Below
2026-05-24	61.01	Below	Below
2026-05-23	60.91	Below	Below
2026-05-22	61.26	Below	Below
2026-05-21	61.04	Below	Below
2026-05-20	60.15	Below	Below
2026-05-19	60.21	Below	Below
2026-05-18	59.57	Below	Below
2026-05-17	59.19	Below	Below
2026-05-16	59.25	Below	Below
2026-05-15	59.45	Below	Below
2026-05-14	58.98
2026-05-13	58.33
2026-05-12	58.60
2026-05-11	58.65
2026-05-10	58.26
2026-05-09	58.57
2026-05-08	58.16
2026-05-07	58.42
2026-05-06	56.70
2026-05-05	55.73
2026-05-04	55.44
2026-05-03	56.44
2026-05-02	56.72
2026-05-01	57.45
2026-04-30	57.50
2026-04-29	57.18
2026-04-28	56.37
2026-04-27	54.99
2026-04-26	54.05
2026-04-25	54.90
2026-04-24	56.79
2026-04-23	55.98
2026-04-22	54.39
2026-04-21	54.21
2026-04-20	55.43
2026-04-19	56.37
2026-04-18	55.37
2026-04-17	55.54
2026-04-16	55.32
2026-04-15	55.28
2026-04-14	55.25
2026-04-13	53.69
2026-04-12	53.75
2026-04-11	56.06
2026-04-10	56.92
2026-04-09	59.04
2026-04-08	58.82
2026-04-07	58.12
2026-04-06	58.68
2026-04-05	58.29
2026-04-04	59.04
2026-04-03	57.74
2026-04-02	56.83
2026-04-01	56.06
2026-03-31	57.25
2026-03-30	58.33
2026-03-29	59.17
2026-03-28	58.75
2026-03-27	58.51
2026-03-26	57.97
2026-03-25	57.70
2026-03-24	56.97
2026-03-23	56.76
2026-03-22	56.61
2026-03-21	56.52
2026-03-20	56.37
2026-03-19	55.22
2026-03-18	54.41
2026-03-17	54.03
2026-03-16	53.89
2026-03-15	53.60
2026-03-14	53.29
2026-03-13	53.05
2026-03-12	53.04
2026-03-11	53.09
2026-03-10	53.66
2026-03-09	54.40
2026-03-08	54.24
2026-03-07	53.24
2026-03-06	52.70
2026-03-05	52.41
2026-03-04	52.12
2026-03-03	51.75
2026-03-02	51.33
2026-03-01	51.50
2026-02-28	52.00
2026-02-27	52.01
2026-02-26	51.30
2026-02-25	50.62
2026-02-24	50.74
2026-02-23	51.15
2026-02-22	51.04
2026-02-21	50.10
2026-02-20	49.30
2026-02-19	49.39
2026-02-18	49.35
2026-02-17	49.93
2026-02-16	51.50
2026-02-15	51.97
2026-02-14	51.52
2026-02-13	51.19
2026-02-12	51.27
2026-02-11	51.03
2026-02-10	50.33
2026-02-09	50.87
2026-02-08	50.67
2026-02-07	50.40
2026-02-06	50.50
2026-02-05	50.47
2026-02-04	50.38
2026-02-03	50.25
2026-02-02	50.17
2026-02-01	50.15
2026-01-31	50.35
2026-01-30	50.57
2026-01-29	50.62
2026-01-28	50.64
2026-01-27	49.76
2026-01-26	49.62
2026-01-25	49.41
2026-01-24	50.09
2026-01-23	49.33
2026-01-22	49.91
2026-01-21	50.18
2026-01-20	50.36
2026-01-19	50.22
2026-01-18	50.72
2026-01-17	50.93
2026-01-16	51.05
2026-01-15	51.05
2026-01-14	51.10
2026-01-13	51.68
2026-01-12	50.60
2026-01-11	51.16
2026-01-10	51.19
2026-01-09	51.12
2026-01-08	51.06
2026-01-07	51.68
2026-01-06	51.75
2026-01-05	51.41
2026-01-04	50.50
2026-01-03	51.21
2026-01-02	51.41
2026-01-01	51.14

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)
2026-01-01	4808.46	50.89	51.14
2026-01-02	4992.67	50.93	51.41
2026-01-03	6736.67	50.66	51.21
2026-01-04	9731.75	50.43	50.50
2026-01-05	10942.54	51.54	51.41
2026-01-06	10861.21	51.56	51.75
2026-01-07	10964.63	51.53	51.68
2026-01-08	11088.67	51.00	51.06
2026-01-09	10772.75	51.26	51.12
2026-01-10	9254.79	51.16	51.19
2026-01-11	8166.50	51.08	51.16
2026-01-12	7109.75	50.81	50.60
2026-01-13	6260.83	50.72	51.68
2026-01-14	5540.75	50.60	51.10
2026-01-15	4977.88	50.48	51.05
2026-01-16	4444.46	50.47	51.05
2026-01-17	3966.33	50.28	50.93
2026-01-18	3916.04	50.07	50.72
2026-01-19	3485.46	49.72	50.22
2026-01-20	3482.96	49.69	50.36
2026-01-21	3489.71	49.55	50.18
2026-01-22	3495.46	49.33	49.91
2026-01-23	3511.83	49.05	49.33
2026-01-24	3518.92	49.33	50.09
2026-01-25	3521.79	49.20	49.41
2026-01-26	3518.75	49.05	49.62
2026-01-27	3529.50	49.21	49.76
2026-01-28	3100.96	49.56	50.64
2026-01-29	2569.29	49.57	50.62
2026-01-30	2511.13	49.62	50.57
2026-01-31	3926.67	49.45	50.35
2026-02-01	4922.58	49.20	50.15
2026-02-02	4859.88	49.39	50.17
2026-02-03	4877.29	49.37	50.25
2026-02-04	4881.83	49.51	50.38
2026-02-05	4889.96	49.50	50.47
2026-02-06	4898.74	49.54	50.50
2026-02-07	4874.17	49.48	50.40
2026-02-08	4560.75	49.57	50.67
2026-02-09	4513.04	50.00	50.87
2026-02-10	4073.96	49.59	50.33
2026-02-11	3578.00	49.73	51.03
2026-02-12	3472.46	50.05	51.27
2026-02-13	3068.29	50.15	51.19
2026-02-14	2568.08	50.53	51.52
2026-02-15	2512.79	50.43	51.97
2026-02-16	2525.92	50.34	51.50
2026-02-17	2514.75	50.01	49.93
2026-02-18	2504.96	49.32	49.35
2026-02-19	2513.92	48.66	49.39
2026-02-20	2537.71	48.92	49.30
2026-02-21	2529.17	49.38	50.10
2026-02-22	2536.50	49.73	51.04
2026-02-23	4076.33	49.98	51.15
2026-02-24	5028.75	49.58	50.74
2026-02-25	5040.71	49.29	50.62
2026-02-26	4921.50	49.62	51.30
2026-02-27	4467.63	50.35	52.01
2026-02-28	3956.88	50.03	52.00
2026-03-01	3429.29	49.48	51.50
2026-03-02	2889.75	49.48	51.33
2026-03-03	2384.92	49.67	51.75
2026-03-04	1932.25	50.09	52.12
2026-03-05	1530.63	50.37	52.41
2026-03-06	1512.46	50.39	52.70
2026-03-07	1533.42	51.01	53.24
2026-03-08	1473.74	51.16	54.24
2026-03-09	2064.33	51.00	54.40
2026-03-10	2494.88	51.12	53.66
2026-03-11	2493.67	50.63	53.09
2026-03-12	2494.33	50.55	53.04
2026-03-13	2487.63	50.48	53.05
2026-03-14	2446.96	50.67	53.29
2026-03-15	2496.46	50.88	53.60
2026-03-16	2466.67	50.77	53.89
2026-03-17	2491.54	50.74	54.03
2026-03-18	2495.33	51.10	54.41
2026-03-19	2277.67	52.48	55.22
2026-03-20	2226.54	53.03	56.37
2026-03-21	2204.88	53.13	56.52
2026-03-22	1882.04	53.20	56.61
2026-03-23	1810.17	53.08	56.76
2026-03-24	1537.46	53.72	56.97
2026-03-25	1519.88	53.74	57.70
2026-03-26	1207.79	54.47	57.97
2026-03-27	1182.75	54.63	58.51
2026-03-28	1183.29	54.18	58.75
2026-03-29	1184.33	54.24	59.17
2026-03-30	1161.33	54.22	58.33
2026-03-31	1139.63	53.75	57.25
2026-04-01	1161.42	54.05	56.06
2026-04-02	1162.00	54.27	56.83
2026-04-03	1160.04	55.01	57.74
2026-04-04	1390.25	54.56	59.04
2026-04-05	1505.13	54.60	58.29
2026-04-06	1513.96	54.43	58.68
2026-04-07	1508.63	54.22	58.12
2026-04-08	1511.71	54.88	58.82
2026-04-09	1819.79	54.30	59.04
2026-04-10	1999.54	54.53	56.92
2026-04-11	4665.04	53.97	56.06
2026-04-12	7275.63	52.66	53.75
2026-04-13	7248.63	52.52	53.69
2026-04-14	7238.63	54.05	55.25
2026-04-15	6567.29	53.80	55.28
2026-04-16	6449.79	53.92	55.32
2026-04-17	6493.08	54.69	55.54
2026-04-18	6461.46	53.69	55.37
2026-04-19	6497.75	54.78	56.37
2026-04-20	6567.38	54.30	55.43
2026-04-21	7140.71	53.17	54.21
2026-04-22	7497.83	53.40	54.39
2026-04-23	7439.96	54.97	55.98
2026-04-24	6991.13	55.23	56.79
2026-04-25	6591.29	53.70	54.90
2026-04-26	6126.08	52.81	54.05
2026-04-27	5528.67	53.66	54.99
2026-04-28	5063.17	54.81	56.37
2026-04-29	4564.17	55.09	57.18
2026-04-30	4063.92	54.73	57.50
2026-05-01	3611.71	54.61	57.45
2026-05-02	3167.58	54.27	56.72
2026-05-03	3071.58	54.45	56.44
2026-05-04	3088.79	54.36	55.44
2026-05-05	3075.04	53.45	55.73
2026-05-06	3073.50	54.49	56.70
2026-05-07	3051.58	55.03	58.42
2026-05-08	3763.88	55.05	58.16
2026-05-09	4017.21	55.68	58.57
2026-05-10	4004.25	55.22	58.26
2026-05-11	3958.71	55.85	58.65
2026-05-12	3562.50	55.12	58.60
2026-05-13	3519.79	55.50	58.33
2026-05-14	3504.25	56.43	58.98
2026-05-15	3491.58	56.51	59.45
2026-05-16	3472.21	56.70	59.25
2026-05-17	3033.29	57.46	59.19
2026-05-18	2976.54	56.74	59.57
2026-05-19	2613.63	56.60	60.21
2026-05-20	2095.75	56.00	60.15
2026-05-21	2036.13	56.75	61.04
2026-05-22	2019.95	56.45	61.26
2026-05-23	2008.33	56.47	60.91
2026-05-24	1985.38	56.93	61.01
2026-05-25	2007.38	56.81	60.78
2026-05-26	2008.17	57.56	59.64
2026-05-27	2021.75	57.13	60.46
2026-05-28	2029.13	56.91	59.99
2026-05-29	2028.58	56.64	59.81
2026-05-30	2026.00	56.73	60.72
2026-05-31	1947.04	57.15	61.68
2026-06-01	2006.08	57.55	62.09
2026-06-02	1566.92	57.60	62.61
2026-06-03	1180.38	57.88	63.79
2026-06-04	1149.29	58.68	65.57
2026-06-05	1155.63	58.60	66.22
2026-06-06	1149.29	58.38	64.74
2026-06-07	1150.75	59.41	64.14
2026-06-08	1146.08	58.68	64.87
2026-06-09	1073.08	59.10	65.45
2026-06-10	1137.88	59.66	66.51
2026-06-11	1426.96	59.12	66.79
2026-06-12	1876.83	58.65	65.24
2026-06-13	2035.54	59.49	64.70
2026-06-14	2032.25	59.41	64.46
2026-06-15	2030.08	59.75	64.83
2026-06-16	2314.29	59.46	64.39
2026-06-17	2448.13	59.69	63.88
2026-06-18	2797.17	59.43	63.50
2026-06-19	3617.58	59.62	62.41
2026-06-20	3918.54	58.89	62.07
2026-06-21	3967.42	59.58	62.01
2026-06-22	3955.42	58.86	61.92
2026-06-23	3973.46	59.01	61.66
2026-06-24	3991.33	59.21	61.82
2026-06-25	4000.71	59.47	61.92
2026-06-26	4030.50	59.63	61.68
2026-06-27	3938.50	59.77	62.10
2026-06-28	4017.13	61.30	62.86
2026-06-29	3969.67	62.14	64.24
2026-06-30	4094.29	60.85	63.75
2026-07-01	4091.08	60.97	63.21
2026-07-02	4089.33	61.08	63.26
2026-07-03	4066.63	61.42	63.69
2026-07-04	4032.67	61.49	64.08
2026-07-05	4124.25	61.90	64.01
2026-07-06	4134.25	62.07	64.18
2026-07-07	4037.29	62.14	64.24
2026-07-08	4028.79	62.35	64.46
2026-07-09	4344.29	62.78	64.93
2026-07-10	4532.96	63.13	65.32
2026-07-11	4546.25	63.33	65.29
2026-07-12	4544.54	63.36	64.78
2026-07-13	4541.83	63.00	64.50
2026-07-14	4536.96	63.20	65.90
2026-07-15	4544.58	63.31	65.85
2026-07-16	4538.46	63.56	65.62
2026-07-17	4541.75	64.45	65.92
2026-07-18	4506.17	64.90	66.62
2026-07-19	4467.79	65.17	66.92
2026-07-20	4513.88	65.53	67.28
2026-07-21	4531.08	65.78	67.93
2026-07-22	4478.88	65.58	68.07
2026-07-23	4488.88	64.90	67.07
2026-07-24	4493.63	65.18	67.06
2026-07-25	4484.10	66.01	67.49
2026-07-26	4830.42	66.51	68.07
2026-07-27	5011.71	66.58	68.29
2026-07-28	5018.00	66.23	68.09
2026-07-29	5000.79	65.09	67.54
2026-07-30	5022.58	65.13	66.94
2026-07-31	5034.79	65.93	67.04
2026-08-01	4984.29	65.39	67.66
2026-08-02	4953.88	65.80	67.69
2026-08-03	4954.71	66.12	68.21
2026-08-04	4967.13	61.74	65.63
2026-08-05	4974.33	60.33	62.70
2026-08-06	4966.50	60.48	62.65

Query Notes

Data Methods

Data Courtesy of CDEC
Hourly data for American R blw Watt Ave Bridge (AWB) is retrieved from CDEC on a daily basis.
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.
CBR calculates Daily Average values based on CBR cleaned hourly values.
Query for daily average water temperature for selected year.
Examine daily average data record for 65°F exceedance.
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.