Costilla County Lake Quality
Colorado, 1 lakes, average grade B (Good)
Costilla County has 1 graded lakes — a thin enough sample that one or two stressed lakes can move the county average noticeably. Use the per-lake pages below for what actually matters. The county-wide average lands at B — solid water quality with most lakes carrying clear summer transparency and low-to-moderate phosphorus.
The county's lakes lean shallow, which makes the grades sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest lake on the books is Mountain Home Reservoir (B); the most-stressed is Mountain Home Reservoir (B).
Quick Answers for Costilla County
Planning a trip? Check special fishing regulations for Mountain Home Reservoir — or check the official Colorado fishing regulations.
All Lakes in Costilla County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Mountain Home Reservoir | B | 14.4 ft | - |
Other Counties in Colorado
See how Costilla County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 12 states.
Where to stay near Costilla County
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Source: EPA National Aquatic Resource Surveys, 2026.