Delta County Lake Quality
Colorado, 4 lakes, average grade C (Fair)
Delta County has 4 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. Delta County averages to a C. The distribution behind that average matters more than the letter: a few stressed lakes versus many decent ones can produce the same average as the inverse.
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. Island Lake (A) is the cleanest in the county.
Quick Answers for Delta County
Planning a trip? Check special fishing regulations for Island Lake — or check the official Colorado fishing regulations.
All Lakes in Delta County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Island Lake | A | 16.7 ft | - |
| 2 | Eggleston Lake | D | 4.9 ft | - |
| 3 | Sweitzer Reservoir | D | 3.6 ft | - |
| 4 | Crawford Reservoir | D | 5.6 ft | - |
Other Counties in Colorado
See how Delta 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 Delta County
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Source: EPA National Aquatic Resource Surveys, 2026.