Pleasant Lake-Southeast Cove
Merrimack County, New Hampshire604 acresView mapDirections
NHDES publishes the water-quality measurements for Pleasant Lake-Southeast Cove. Here is what has been measured.
- Oligotrophic
- Impaired · Mercury
- Limited data
Pleasant Lake-Southeast Cove in Merrimack County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 5 µg/L. Surface area: 604 acres.
Pleasant Lake-Southeast Cove is a 604-acre cold, clear oligotrophic lake in Merrimack County, New Hampshire. Compared to the 40 other monitored lakes in Merrimack County, Pleasant Lake-Southeast Cove ranks #20 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2024-09-10. Methodology: how these readings are compared.
Swimming conditions
Readings onlyLimited data
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Pleasant Lake-Southeast Cove is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, oxygen depletion (low DO), pH / acidity. Check local advisories before you swim.
Whether Pleasant Lake-Southeast Cove 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 Pleasant Lake-Southeast Cove
These are the measurements NHDES publishes for Pleasant Lake-Southeast Cove, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. Phosphorus 5 µg/L. TSI 27.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | No reading How deep a black-and-white disk stays visible from the surface. Higher is clearer. | |
| Total phosphorus | 5µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 27 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Pleasant Lake-Southeast Cove
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
604 acres
No bathymetric survey has been published for Pleasant Lake-Southeast Cove, so its depth is not documented here.
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Fishing Pleasant Lake-Southeast Cove
Reservoir Info (USACE NID)
Pleasant Lake-Southeast Cove is a man-made reservoir impounded by the Pleasant Lake Dam (completed 1850), built primarily for recreation on the Tr Blackwater River; earth-type dam, 13 ft tall and 360 ft long.
- Surface area
- 604 ac
- Normal storage
- 6,806 ac-ft
- Max storage
- 9,295 ac-ft
- Drainage area
- 11.03 sq mi
- Hazard class
- High
- Owner
- TOWN OF NEW LONDON
Source: USACE National Inventory of Dams, NID ID NH00362 · Operator website · Matched by proximity (0.89 km)
EPA Impairment Status
Pleasant Lake-Southeast Cove is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Aquatic life, Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NHLAK700030402-02-01 · Official waterbody report
Nearby Lakes in Merrimack County
Frequently asked questions about Pleasant Lake-Southeast Cove
Where is Pleasant Lake-Southeast Cove?
- Pleasant Lake-Southeast Cove is a lake in Merrimack County, New Hampshire. Its water-quality measurements are published by NHDES and shown on this page as reported.
What is the water quality of Pleasant Lake-Southeast Cove?
- Pleasant Lake-Southeast Cove in Merrimack County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 5 µg/L. Surface area: 604 acres.
Is Pleasant Lake-Southeast Cove safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Pleasant Lake-Southeast Cove is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, oxygen depletion (low DO), pH / acidity. Check local advisories before you swim.
Explore Pleasant Lake-Southeast Cove across LakeQuality
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Where this data comes from
10 measurements from 1 monitoring station, 2022–2024. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- New Hampshire Department Of Environmental Services (BEACH)
1111330010 samples · 2022–2024
Analytical methods
- 10-115-01-1 F ~ LACHAT; Total Phosphorus- Manual persulfate digest
- Phosphorus by Two Reagent Colorimetry
- 2130 B ~ Nephelometric Method
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database