Lake Farmington Deep
San Juan County, New Mexico198 acresView mapDirections
Not enough samples to grade — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). No letter yet. Here is what we do have.
- Impaired · Mercury
- Limited data
Lake Farmington Deep in San Juan County, New Mexico is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 9.8 ft visibility. Chlorophyll-a (algae): 2.4 µg/L. Surface area: 198 acres.
- Clarity
- 9.8 ft
- Area
- 198 acres
- Chlorophyll-a
- 2.4 µg/L
- Trend
- ↑ Improving
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Watch Lake Farmington Deep’s letter
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Why Lake Farmington Deep has no grade
We grade a lake only when the monitoring record supports a letter: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Lake Farmington Deep, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). Sampling here has recorded water clarity and algae (chlorophyll-a), but not phosphorus.
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by NMED and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Lake Farmington Deep is a 198-acre lake in San Juan County, New Mexico. Overall water quality is improving over recent sampling years.
Source: EPA Water Quality Portal sampling records, NMED, last sampled 2018-10-17. Grade methodology: LakeQuality methodology.
What Lake Farmington Deep is good for
From access and monitoring records, not editorial picks.
- Clear water9.8 ft of visibility
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Lake Farmington Deep is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
Water quality measurements for Lake Farmington Deep
These readings exist but are not enough for an A–F grade — see why.
Moderate clarity, visible to about 9.8 ft. Chlorophyll-a 2.4 µg/L. TSI 42.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 9.8 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | 2.4 µg/L | Not graded |
| Trophic State Index (TSI) | 42 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 198 acres |
No bathymetric survey has been published for Lake Farmington Deep, so its depth is not documented here.
Fishing Lake Farmington Deep
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.04 m/yr | 2 |
| Chlorophyll-a | ↑ Improving | -0.24 µg/L/yr | 2 |
Reservoir Info (USACE NID)
Lake Farmington Deep is a man-made reservoir impounded by the Farmington Lake Dam (completed 1964), built primarily for water supply on the Animas River-Os; earth-type dam, 117 ft tall and 1,075 ft long.
- Surface area
- 198 ac
- Normal storage
- 6,703 ac-ft
- Max storage
- 8,470 ac-ft
- Drainage area
- 3.11 sq mi
- Hazard class
- High
- Owner
- CITY OF FARMINGTON
Source: USACE National Inventory of Dams, NID ID NM00302 · Operator website · Matched by proximity (0.05 km)
EPA Impairment Status
Lake Farmington Deep is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit NM-9000.B_006 · Official waterbody report · Matched by proximity (0.83 km)
Nearby Lakes in San Juan County
Frequently asked questions about Lake Farmington Deep
Where is Lake Farmington Deep?
- Lake Farmington Deep is a lake in San Juan County, New Mexico. LakeQuality has not rated this lake (UNRATED) — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
What is the water quality grade for Lake Farmington Deep?
- Lake Farmington Deep in San Juan County, New Mexico is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 9.8 ft visibility. Chlorophyll-a (algae): 2.4 µg/L. Surface area: 198 acres.
Is Lake Farmington Deep safe to swim in?
- The letter is not a swimming clearance. Lake Farmington Deep is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
Explore Lake Farmington Deep across LakeQuality
Planning a trip around Mesa Verde?
Lake Farmington Deep is about 37 miles from Mesa Verde National Park. Crowds there swing hard by season, so the month you pick changes both how busy the park is and what lodging costs.
Best time to visit Mesa Verde →More New Mexico Lake Rankings
Other Lakes in New Mexico
Mesotrophic Lakes in New Mexico
Where this data comes from
6 measurements from 1 monitoring station, 2017–2018. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- NM Environmental Dept./SWQB
21NMEX_WQX6 samples · 2017–2018
Analytical methods
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database