Where is Thermalito Afterbay?

Thermalito Afterbay is a lake in Butte County, California. Its water-quality measurements are published by SWRCB and shown on this page as reported.

Are there boat ramps on Thermalito Afterbay?

Thermalito Afterbay has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Thermalito Afterbay (Monument Hill Boat), Thermalito Afterbay. Public access is listed as yes.

Can I fish at Thermalito Afterbay?

Thermalito Afterbay has 2 documented boat landings in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by California's fish and wildlife agency, so check its current regulations before you go.

Thermalito Afterbay

Butte County, California4,075 acresView map Directions

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

Area

4,075 acres

Surface area

Shoreline

28.1 mi

Measured length

Impaired · Mercury
Public access

See the measurements Directions Where to stay

Thermalito Afterbay in Butte County, California has water-quality measurements published by SWRCB, shown here as reported. Surface area: 4075 acres.

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Thermalito Afterbay is a 4,075-acre lake in Butte County, California. Limited fish-species data available. Public access is available with 2 public boat landings.

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

What Thermalito Afterbay is good for

From access and monitoring records, not editorial picks.

Boat launch2 documented ramps
Big water4,075 acres

Swimming conditions

No reading

Not rated

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

Whether Thermalito Afterbay 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 Thermalito Afterbay

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

No clarity data. TSI undefined.

Ask about Thermalito Afterbay

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

Lake Details

Surface area

4,075 acres

Shoreline

28.1 mi

Public access

Yes

Listed by SWRCB

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

Recreation & Access

Boat Landings

Yes

Public Access

Thermalito Afterbay (Monument Hill Boat)Public
Thermalito AfterbayPublic

Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps

Stays via Stay22

Stays near Thermalito Afterbay

Compare lakeside cabins, hotels, and vacation rentals near Thermalito Afterbay in Butte 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 Thermalito Afterbay

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Fishing Thermalito Afterbay

→ Thermalito Afterbay fishing regulations (limits, seasons, special rules)

EPA Impairment Status

Thermalito Afterbay 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 CAL5154000020000209142817 · Official waterbody report

Nearby Lakes in Butte County

Thermalito Forebay4.3 miView →Thermalito Diversion Pool9.2 miView →Miners Ranch Reservoir11.9 miView →Lake Wyandotte14.1 miView →Lake OrovilleOligotrophic14.8 miView →Eddy Lake16.2 miView →

Frequently asked questions about Thermalito Afterbay

Where is Thermalito Afterbay?: Thermalito Afterbay is a lake in Butte County, California. Its water-quality measurements are published by SWRCB and shown on this page as reported.
What is the water quality of Thermalito Afterbay?: Thermalito Afterbay in Butte County, California has water-quality measurements published by SWRCB, shown here as reported. Surface area: 4075 acres.
Is Thermalito Afterbay safe to swim in?: Nutrient and algae readings are not a swimming clearance. Thermalito Afterbay is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
Are there boat ramps on Thermalito Afterbay?: Thermalito Afterbay has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Thermalito Afterbay (Monument Hill Boat), Thermalito Afterbay. Public access is listed as yes.
Can I fish at Thermalito Afterbay?: Thermalito Afterbay has 2 documented boat landings in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by California's fish and wildlife agency, so check its current regulations before you go.