Back Lake
Coos County, New Hampshire347 acresView mapDirections
No nutrient or algae sampling on record from NHDES for this lake.
- Impaired · Biotoxins
- 15 ft max depth
Back Lake in Coos County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Maximum depth: 15 ft. Surface area: 347 acres.
Back Lake is a 347-acre lake in Coos County, New Hampshire with a maximum depth of 15 feet (7-foot average).
Source: EPA Water Quality Portal sampling records, your state environmental agency. Methodology: how these readings are compared.
Swimming conditions
No readingBacteria advisory
Nutrient and algae readings are not a swimming clearance. Back Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for biotoxins, mercury. Check local advisories before you swim.
Whether Back Lake is safe to swim in today is a call for the New Hampshire Department of Environmental Services and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Back Lake
These are the measurements NHDES publishes for Back Lake, 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.
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Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
15 ft
Average depth
6.6 ft
Surface area
347 acres
Shoreline
4 mi
The depth above comes from a bathymetric survey of this lake, not from a regional estimate.
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Fishing Back Lake
EPA Impairment Status
Back Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Fish consumption, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NHLAK801010203-01-01 · Official waterbody report
Nearby Lakes in Coos County
Frequently asked questions about Back Lake
Where is Back Lake?
- Back Lake is a lake in Coos County, New Hampshire. Its water-quality measurements are published by NHDES and shown on this page as reported.
What is the water quality of Back Lake?
- Back Lake in Coos County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Maximum depth: 15 ft. Surface area: 347 acres.
Is Back Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Back Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for biotoxins, mercury. Check local advisories before you swim.
How deep is Back Lake?
- Back Lake has a maximum depth of 15 feet and an average depth of 6.6 feet. The lake covers 347 acres.
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Where this data comes from
Measurements for Back Lake come from the EPA Water Quality Portal. Per-sample source details are not recorded for this lake.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database