Todd Lake-Deep Spot
Merrimack County, New HampshireView mapDirections
NHDES publishes the water-quality measurements for Todd Lake-Deep Spot. Here is what has been measured.
- Mesotrophic
- Impaired · Mercury
- Limited data
Todd Lake-Deep Spot in Merrimack County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 15.8 µg/L. Chlorophyll-a (algae): 4.7 µg/L.
Todd Lake-Deep Spot is a mesotrophic lake in Merrimack County, New Hampshire. Compared to the 40 other monitored lakes in Merrimack County, Todd Lake-Deep Spot ranks #39 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2024-06-06. 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. Todd Lake-Deep Spot is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, pH / acidity. Check local advisories before you swim.
Whether Todd Lake-Deep Spot 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 Todd Lake-Deep Spot
These are the measurements NHDES publishes for Todd Lake-Deep Spot, 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 15.8 µg/L. Chlorophyll-a 4.7 µg/L. TSI 45.
| 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 | 15.8µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 4.7µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 45 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
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Fishing Todd Lake-Deep Spot
EPA Impairment Status
Todd Lake-Deep Spot 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 NHLAK700030301-02 · Official waterbody report
Nearby Lakes in Merrimack County
Frequently asked questions about Todd Lake-Deep Spot
Where is Todd Lake-Deep Spot?
- Todd Lake-Deep Spot 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 Todd Lake-Deep Spot?
- Todd Lake-Deep Spot in Merrimack County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 15.8 µg/L. Chlorophyll-a (algae): 4.7 µg/L.
Is Todd Lake-Deep Spot safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Todd Lake-Deep Spot is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, pH / acidity. Check local advisories before you swim.
Explore Todd Lake-Deep Spot across LakeQuality
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Where this data comes from
11 measurements from 1 monitoring station, 2021–2024. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- New Hampshire Department Of Environmental Services (BEACH)
1111330011 samples · 2021–2024
Analytical methods
- 10-115-01-1 F ~ LACHAT; Total Phosphorus- Manual persulfate digest
- CHLOROPHYLL A-B-C DETERMINATION (MODIFIED)
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