Where is Briones Reservoir?

Briones Reservoir is a lake in Contra Costa County, California. Its water-quality measurements are published by SWRCB and shown on this page as reported.

Briones Reservoir

Contra Costa County, California669 acresView map Directions

No nutrient or algae sampling on record from SWRCB for this lake.

Area

669 acres

Surface area

Shoreline

12.6 mi

Measured length

Impaired · Mercury
Limited data

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Briones Reservoir in Contra Costa County, California has water-quality measurements published by SWRCB, shown here as reported. Surface area: 669 acres.

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Briones Reservoir is a 669-acre lake in Contra Costa County, California.

Source: EPA Water Quality Portal sampling records, your state environmental agency. Methodology: how these readings are compared.

Swimming conditions

No reading

Limited data

Nutrient and algae readings are not a swimming clearance. Briones Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.

Whether Briones Reservoir is safe to swim in today is a call for the California State Water Resources Control Board and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.

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Water quality measurements for Briones Reservoir

These are the measurements SWRCB publishes for Briones Reservoir, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.

No clarity data.

Ask about Briones Reservoir

Answers come straight from the public measurements and survey records on this page.

Lake Details

Surface area

669 acres

Shoreline

12.6 mi

No bathymetric survey has been published for Briones Reservoir, so its depth is not documented here.

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Stays near Briones Reservoir

Compare lakeside cabins, hotels, and vacation rentals near Briones Reservoir in Contra Costa County, California — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.

Top-rated places to stay near Briones Reservoir

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Fishing Briones Reservoir

→ Briones Reservoir fishing regulations (limits, seasons, special rules)

EPA Impairment Status

Briones Reservoir is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).

Causes of impairment

Mercury

Designated uses not supporting: Fish consumption, Other.

Source: EPA ATTAINS assessment unit CAL2066001120091208101107 · Official waterbody report

Nearby Lakes in Contra Costa County

Lafayette Reservoir3.7 miView →San Pablo Reservoir3.3 miView →Lake Anza12.3 ft clear4.1 miView →Mallard Reservoir10.1 miView →Contra Loma Reservoir4.1 ft clear—View →Antioch Municipal Reservoir—View →

Frequently asked questions about Briones Reservoir

Where is Briones Reservoir?: Briones Reservoir is a lake in Contra Costa County, California. Its water-quality measurements are published by SWRCB and shown on this page as reported.
What is the water quality of Briones Reservoir?: Briones Reservoir in Contra Costa County, California has water-quality measurements published by SWRCB, shown here as reported. Surface area: 669 acres.
Is Briones Reservoir safe to swim in?: Nutrient and algae readings are not a swimming clearance. Briones Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.