Reservoir · Boulder County · CO
Is Leggett and Hillcrest Reservoir safe to swim?
No advisory or algae bloom reported for this water today.
Updated July 20, 2026 · EPA CyAN satellite
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What's in the water at Leggett and Hillcrest Reservoir right now
As of July 20, 2026, Leggett and Hillcrest Reservoir in Boulder County, Colorado is clear to swim. Satellite imagery detected no blue-green algae bloom as of July 19, 2026. Rainfall over the past week totaled 0.0 in, which can wash bacteria and nutrients into the water.
Blue-green algae at Leggett and Hillcrest Reservoir
Leggett and Hillcrest Reservoir is a reservoir in Boulder County, Colorado covering about 0.8 sq mi, the 64th-largest of the 107 lakes SwimZone monitors in Colorado. Satellite imagery detected no blue-green algae bloom as of July 19, 2026.
Blue-green algae (cyanobacteria) blooms are most common from midsummer into early fall, when the water is warm, calm, and rich in nutrients from runoff. They can produce toxins that make people sick and can be rapidly fatal to dogs, so skip water that looks green, scummy, or like spilled paint, and keep children and pets out of it.
Bloom history at Leggett and Hillcrest Reservoir
From EPA CyAN's satellite archive
Over 7 summers of satellite monitoring since 2020, Leggett and Hillcrest Reservoir has not reached a blue-green algae advisory level. Conditions can still change quickly, so check the current read before you swim.
Frequently asked: swimming in Leggett and Hillcrest Reservoir
- Is it safe to swim in Leggett and Hillcrest Reservoir right now?
- Leggett and Hillcrest Reservoir is clear to swim today. Satellite imagery detected no blue-green algae bloom as of July 19, 2026. Conditions can change quickly with wind, heat, and rain, so check the posted signs and look at the water before you get in.
- Does Leggett and Hillcrest Reservoir have blue-green algae (cyanobacteria)?
- No blue-green algae bloom is detectable at Leggett and Hillcrest Reservoir as of July 19, 2026 (below the satellite's roughly 10,000 cells/mL detection limit). Cyanobacteria can still appear within hours in warm, calm, nutrient-rich water, so look before you swim.
- Can dogs swim in Leggett and Hillcrest Reservoir?
- No bloom is detected at Leggett and Hillcrest Reservoir today, but dogs are much more vulnerable to blue-green algae than people, and blooms can form within hours. Always keep dogs away from water that looks green, scummy, or discolored, and rinse them off after swimming.
- How often does Leggett and Hillcrest Reservoir have blue-green algae blooms?
- Over 7 summers of satellite monitoring since 2020, Leggett and Hillcrest Reservoir has not reached a blue-green algae advisory level. Conditions can still change quickly, so check the current read before you swim.
- How many Colorado lakes and beaches are unsafe for swimming today?
- Today, 26 Colorado waters are above a safe-contact threshold and 3 more warrant caution, out of 113 monitored waters SwimZone tracks in the state.
- How is Leggett and Hillcrest Reservoir's water quality measured?
- SwimZone builds this read from EPA CyAN satellite imagery for blue-green algae, official beach and fecal-bacteria advisories where a program monitors Leggett and Hillcrest Reservoir, and a recent-rainfall overlay, all refreshed daily. It was last updated July 20, 2026.