San Juan County Lake Quality
New Mexico, 14 lakes — no lake here has enough monitoring data for a grade
San Juan County holds 14 monitored lakes. With a sample that small the county-level summary describes those specific waters, not necessarily every water body in the county. No lake in San Juan County has enough sampling behind it for an A–F grade yet. The 14 monitored lakes below carry whatever clarity, phosphorus, and chlorophyll-a measurements exist.
Most of the county's monitored lakes are shallow, under 50 feet, which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed.
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Quick Answers for San Juan County
Planning a trip? Check special fishing regulations for Lake Farmington Deep — or check the official New Mexico fishing regulations.
All Lakes in San Juan County
14 lakes · 0 graded, 14 not rated0 graded lakes · 14 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| NRLake Farmington DeepSan Juan | NR | 9.8 ft | No recent samples | 2.4 µg/L | No recent samples | Not recorded | |
| NRFour Mile ReservoirSan Juan | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBlack LakeSan Juan | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRJuans LakeSan Juan | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRLong LakeSan Juan | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRLittle White Cone LakeSan Juan | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBlack LakeSan Juan | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRToadlena LakeSan Juan | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRCaptain Tom ReservoirSan Juan | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRMeadows ReservoirSan Juan | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRYoungs LakeSan Juan | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRMorgan LakeSan Juan | NR | No recent samples | No recent samples | No recent samples | No recent samples | ✓ Public | |
| NRJackson LakeSan Juan | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRTocito LakeSan Juan | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded |
NR = not rated: there is not enough recent sampling to support a letter. That is EPA Integrated Reporting Category 3 (insufficient information), not a failing grade. How grading works.
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Other Counties in New Mexico
See how San Juan County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all United States (49 states), Canada (Ontario, Québec, Nova Scotia, British Columbia and Newfoundland and Labrador), and 38 other country hubs..
Source: EPA National Aquatic Resource Surveys, 2026.