The Reservoir met the temperature standards established for the Class I Warm Water Aquatic Life classification established by the Water Quality Control Commission (WQCC) in Regulation No. 31 (Reg 31) of 26.2 ˚C Maximum Weekly Average Temperature (MWAT) and 29.3 ˚C Daily Maximum (DM), as adopted in Regulation 38 for the Reservoir.

Daily Temperature Profile (˚C) on monitoring buoy, Cherry Creek Reservoir, WY 2024

Click the image for a larger graph

Regulation 31 requires dissolved oxygen (DO) concentrations in the upper portion of a lake or reservoir, shall remain at or above  5.0 mg/L. If concentrations are low near the bottom, adequate refuge for aquatic life with DO levels greater than 5.0 mg/L needs to be available at other depths in the reservoir during the same time period. Although low DO concentrations were observed at depth during the summer months of WY 2025, the DO standard was attained since concentrations in the mid and upper portions of the water column were sufficient during the monitoring events.  Reduced DO concentrations in deeper waters are common during the warmer months and are typically associated with microbial activity or decomposition in the hypolimnion and sediments.

During WY 2025, the pH met the minimum and maximum standards of 6.5 and 9.0, based on the annual 15th and 85th percentiles. Higher pH values are usually correlated with higher productivity and elevated chlorophyll-a in the reservoir.

pH Depth Profile from CCR-2, Cherry Creek Reservoir, WY 2025 (click the image for larger graph).

Useful Links

• link Monitoring Report: Executive Summary Reservoir Highlights