[2022 AR] Chlorophyll-α

2022 Report



The chlorophyll-ɑ concentrations in the Reservoir exceeded the growing season standard for 2022.

The Reservoir chlorophyll-α growing season (July through September) concentration was 27.3 ug/L, which exceeds the 18 ug/L growing season standard. The seasonal mean concentration is measured in the upper three meters of the water column (photic zone), with an allowable exceedance frequency of once in five years. The Reservoir has exceeded the chlorophyll-α standard in four of the last five years, and eight of the last ten years.

Why Sample for Chlorophyll-α?

CCBWQA samples for chlorophyll-α because it can tell us about the amount of algae in the Reservoir, and high levels of algae may impact the Reservoir's beneficial uses. Chlorophyll-ɑ is also an enforceable water quality standard for the Reservoir that the Water Quality Control Division uses in its biennial assessment of water quality in the Reservoir.

Useful Links


Seasonal Mean Concentrations of Chlorophyll-a Measured in Cherry Creek Reservoir

info_outlineEach point on the graph represents a seasonal mean value for samples collected in July, August, and September of that year. The red line represents the chlorophyll a standard for the reservoir. Hover over a point to view the specific value for the corresponding year.

Cherry Creek Reservoir Cholorophyll-a Drilldown

info_outlineEach point on this graph represents a sampling event. The different point colors represent different locations. To learn more about a specific data point, hover over it with your mouse.

Hey! This page is interactive.

  • Hover over a point to view the specific value for the corresponding year.
  • For the Cherry Creek Reservoir Cholorophyll-a Drilldown graph you can change the start and end dates to look at different time periods.
  • Select a season from the dropdown to see results from either summer or annual sampling.