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

Supporting Information

Regional Board 7 - Colorado River Basin Region

Water Body Name:	Q Drain tributary
Water Body ID:	CAR7231000020230823027635
Water Body Type:	River & Stream


DECISION ID	161270	Region 7
Q Drain tributary

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:	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 161270, pH	Region 7
Q Drain tributary

LOE ID:

335873

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB7 Monitoring data for Q Drain tributary to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for pH.

Data Reference:

Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 7

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Colorado River Basin Region's water quality objective for all surface waters states the following: Since the regional waters are somewhat alkaline, pH shall range from 6.0-9.0. Discharges shall not cause any changes in pH detrimental to beneficial water uses.

Objective/Criterion Reference:

Water Quality Control Plan for the Colorado River Basin Region (Includes amendments effective on or before March 30, 2019)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 723STQDRN (Q Drain Tributary at Pound and wister road).

Temporal Representation:

The samples were collected between the dates of 2019-04-10 and 2020-01-14

Environmental Conditions:

QAPP Information:

General SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 161270, pH	Region 7
Q Drain tributary