Deering Lake-Morrotta Bay
Hillsborough County, New HampshireView mapDirections
NHDES publishes the water-quality measurements for Deering Lake-Morrotta Bay. Here is what has been measured.
- Oligotrophic
- Impaired · Mercury
- Limited data
Deering Lake-Morrotta Bay in Hillsborough County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 9.5 µg/L.
Deering Lake-Morrotta Bay is a cold, clear oligotrophic lake in Hillsborough County, New Hampshire. Compared to the 35 other monitored lakes in Hillsborough County, Deering Lake-Morrotta Bay ranks #15 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2025-08-05. 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. Deering Lake-Morrotta Bay 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 Deering Lake-Morrotta Bay 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 Deering Lake-Morrotta Bay
These are the measurements NHDES publishes for Deering Lake-Morrotta Bay, 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 9.5 µg/L. TSI 37.
| 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 | 9.5µg/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. | 37 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
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Fishing Deering Lake-Morrotta Bay
EPA Impairment Status
Deering Lake-Morrotta Bay 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 NHLAK700060601-01 · Official waterbody report
Nearby Lakes in Hillsborough County
Frequently asked questions about Deering Lake-Morrotta Bay
Where is Deering Lake-Morrotta Bay?
- Deering Lake-Morrotta Bay is a lake in Hillsborough County, New Hampshire. Its water-quality measurements are published by NHDES and shown on this page as reported.
What is the water quality of Deering Lake-Morrotta Bay?
- Deering Lake-Morrotta Bay in Hillsborough County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 9.5 µg/L.
Is Deering Lake-Morrotta Bay safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Deering Lake-Morrotta Bay 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.
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Where this data comes from
6 measurements from 1 monitoring station, 2024–2025. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- New Hampshire Department Of Environmental Services (BEACH)
111133006 samples · 2024–2025
Analytical methods
- 10-115-01-1 F ~ LACHAT; Total Phosphorus- Manual persulfate digest
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