Oligotrophic Lakes in Colorado

An oligotrophic lake is what most people picture when they think of pristine northern lake country: clarity to depth, no algal scum, cold water that holds dissolved oxygen all the way to the bottom even in August. Across Colorado, 12 lakes register as oligotrophic — 0% of them break 50 feet of depth, which is the structural condition that underwrites the trophic class. Without depth and a low-nutrient watershed, oligotrophy is hard to sustain.

On our A–F scale, oligotrophic lakes almost always pull an A or B — the same low-nutrient conditions that produce the trophic class also produce the high grade.