Draft California 2026 Integrated Report (303(d) List/305(b) Report)

Supporting Information

Regional Board 5 - Central Valley Region

Water Body Name:	Tenaya Lake (Mariposa County)
Water Body ID:	CAL5376003020200904038890
Water Body Type:	Lake & Reservoir


DECISION ID	161131	Region 5
Tenaya Lake (Mariposa County)

Pollutant:	Alkalinity as CaCO3
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 161131, Alkalinity as CaCO3	Region 5
Tenaya Lake (Mariposa County)

LOE ID:

329658

Pollutant:

Alkalinity as CaCO3

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed USGS California Water Science Center data for Tenaya Lake (Mariposa County) to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 5

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Waters shall not contain chemical constituents in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan for the California Regional Water Quality Control Board Central Valley Region, Sacramento and San Joaquin River Basins; Fifth Edition. Revised May 2018 (with approved amendments)

Evaluation Guideline:

The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: USGS-374955119273500 (TENAYA LK CA).

Temporal Representation:

The samples were collected between the dates of 2014-07-10 and 2014-07-10

Environmental Conditions:

QAPP Information:

QAPP for USGS Data Collected during the 2026 Integrated Report Cycle

QAPP Information Reference(s):

QAPP for USGS Data Collected during the 2026 Integrated Report Cycle


DECISION ID	161126	Region 5
Tenaya Lake (Mariposa County)

Pollutant:	Chloride
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 161126, Chloride	Region 5
Tenaya Lake (Mariposa County)

LOE ID:

329754

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed USGS California Water Science Center data for Tenaya Lake (Mariposa County) to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the upper limit of the range for Chloride. Additionally, 0 of the 1 samples fall within the range, and 1 of 1 samples fall below the threshold.

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 5

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Secondary MCL that is incorporated by reference into the Water Quality Control Plan for the Sacramento and San Joaquin River Basins specifies a range for chloride of 250-500 mg/L assessed as an annual average.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: USGS-374955119273500 (TENAYA LK CA).

Temporal Representation:

The samples were collected between the dates of 2014-07-10 and 2014-07-10

Environmental Conditions:

QAPP Information:

QAPP for USGS Data Collected during the 2026 Integrated Report Cycle

QAPP Information Reference(s):

QAPP for USGS Data Collected during the 2026 Integrated Report Cycle


DECISION ID	165522	Region 5
Tenaya Lake (Mariposa County)

Pollutant:	Specific Conductivity
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 165522, Specific Conductivity	Region 5
Tenaya Lake (Mariposa County)

LOE ID:

330240

Pollutant:

Specific Conductivity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed USGS California Water Science Center data for Tenaya Lake (Mariposa County) to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the upper limit of the range for SpecificConductivity. Additionally, 0 of the 1 samples fall within the range, and 1 of 1 samples fall below the threshold.

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 5

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Secondary MCL that is incorporated by reference into the Water Quality Control Plan for the Sacramento and San Joaquin River Basins specifies a range for specific conductance of 900-1600 uS/cm assessed as an annual average.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: USGS-374955119273500 (TENAYA LK CA).

Temporal Representation:

The samples were collected between the dates of 2014-07-10 and 2014-07-10

Environmental Conditions:

QAPP Information:

QAPP for USGS Data Collected during the 2026 Integrated Report Cycle

QAPP Information Reference(s):

QAPP for USGS Data Collected during the 2026 Integrated Report Cycle


DECISION ID	161128	Region 5
Tenaya Lake (Mariposa County)

Pollutant:	Sulfates
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 161128, Sulfates	Region 5
Tenaya Lake (Mariposa County)

LOE ID:

330342

Pollutant:

Sulfates

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed USGS California Water Science Center data for Tenaya Lake (Mariposa County) to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the upper limit of the range for Sulfate. Additionally, 0 of the 1 samples fall within the range, and 1 of 1 samples fall below the threshold.

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 5

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Secondary MCL that is incorporated by reference into the Water Quality Control Plan for the Sacramento and San Joaquin River Basins specifies a range for sulfate of 250-500 mg/L assessed as an annual average.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: USGS-374955119273500 (TENAYA LK CA).

Temporal Representation:

The samples were collected between the dates of 2014-07-10 and 2014-07-10

Environmental Conditions:

QAPP Information:

QAPP for USGS Data Collected during the 2026 Integrated Report Cycle

QAPP Information Reference(s):

QAPP for USGS Data Collected during the 2026 Integrated Report Cycle


DECISION ID	161129	Region 5
Tenaya Lake (Mariposa County)

Pollutant:	Temperature, water
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 161129, Temperature, water	Region 5
Tenaya Lake (Mariposa County)

LOE ID:

330410

Pollutant:

Temperature, water

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 5

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The natural receiving water temperature of intrastate waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Water Board that such alteration in temperature does not adversely affect beneficial uses (Sacramento-San Joaquin River Basin Plans).

Objective/Criterion Reference:

Evaluation Guideline:

Inland Fishes of California (Moyle 1976) states that for rainbow trout the optimum range for growth and completion of most life stages is 13-21 degrees C (page 129).

Guideline Reference:

Inland Fishes of California

Spatial Representation:

The samples were collected at 1 monitoring site: USGS-374955119273500 (TENAYA LK CA).

Temporal Representation:

The samples were collected between the dates of 2014-07-10 and 2014-07-10

Environmental Conditions:

QAPP Information:

QAPP for USGS Data Collected during the 2026 Integrated Report Cycle

QAPP Information Reference(s):

QAPP for USGS Data Collected during the 2026 Integrated Report Cycle


DECISION ID	161130	Region 5
Tenaya Lake (Mariposa County)

Pollutant:	Total Dissolved Solids
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 161130, Total Dissolved Solids	Region 5
Tenaya Lake (Mariposa County)

LOE ID:

330530

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed USGS California Water Science Center data for Tenaya Lake (Mariposa County) to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the upper limit of the range for Total Dissolved Solids. Additionally, 0 of the 1 samples fall within the range, and 1 of 1 samples fall below the threshold.

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 5

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Secondary MCL that is incorporated by reference into the Water Quality Control Plan for the Sacramento and San Joaquin River Basins specifies a range for total dissolved solids of 500-1000 mg/L assessed as an annual average.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: USGS-374955119273500 (TENAYA LK CA).

Temporal Representation:

The samples were collected between the dates of 2014-07-10 and 2014-07-10

Environmental Conditions:

QAPP Information:

QAPP for USGS Data Collected during the 2026 Integrated Report Cycle

QAPP Information Reference(s):

QAPP for USGS Data Collected during the 2026 Integrated Report Cycle


DECISION ID	161127	Region 5
Tenaya Lake (Mariposa County)

Pollutant:	pH
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 161127, pH	Region 5
Tenaya Lake (Mariposa County)

LOE ID:

330137

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 5

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Water Quality Control Plan, Central Valley Region Sacramento River Basin and San Joaquin River Basin: pH should not be lower than 6.5 or higher than 8.5.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: USGS-374955119273500 (TENAYA LK CA).

Temporal Representation:

The samples were collected between the dates of 2014-07-10 and 2014-07-10

Environmental Conditions:

QAPP Information:

QAPP for USGS Data Collected during the 2026 Integrated Report Cycle

QAPP Information Reference(s):

QAPP for USGS Data Collected during the 2026 Integrated Report Cycle