San Juan County Lake Quality
New Mexico, 7 lakes, average grade B (Good)
Only 7 lakes in San Juan County carry an active grade. The county-level summary is therefore representative of those specific lakes, not necessarily of every water body in the county. With an average grade of B, San Juan County sits comfortably above the {{stateName}} median.
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. Navajo Reservoir (A) is the cleanest in the county.
Quick Answers for San Juan County
Planning a trip? Check special fishing regulations for Navajo Reservoir — or check the official New Mexico fishing regulations.
All Lakes in San Juan County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Navajo Reservoir | A | 16 ft | - |
| 2 | Nla Lake | A | 14.4 ft | 13.9 µg/L |
| 3 | Navajo Reservoir Negro Canyon | A | 6.5 ft | - |
| 4 | Lake Farmington Deep | A | 9.8 ft | - |
| 5 | Nla Lake | C | 10.5 ft | 17000 µg/L |
| 6 | Four Mile Reservoir | D | - | 67 µg/L |
| 7 | Nla Lake | D | 0.8 ft | 159000 µg/L |
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 34 states.
Where to stay near San Juan County
Top-rated places to stay near San Juan County
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a trip to San Juan County?
Get lake water-quality report cards plus the best cabin & lodging deals near San Juan County — straight to your inbox. No spam, unsubscribe anytime.
Source: EPA National Aquatic Resource Surveys, 2026.