[2021 AR] Trophic State Index

2021 Report

Trophic State Index


In WY 2021, the Reservoir’s trophic state was classified as eutrophic to hypereutrophic. Higher TSI values are associated with higher nutrients and more primary productivity (algal growth).

The Trophic State Index (TSI) is a measure of the biological productivity of a water body. The most common TSI uses three water quality parameters to determine the trophic state: Total Phosphorus, Secchi Depth (a measure of water transparency), and Chlorophyll a.

There are four main levels of biological productivity: Oligotrophic (Low), Mesotrophic (Moderate), Eutrophic (High), and Hypereutrophic (Excessive). Higher TSI numbers are associated with increased probabilities of encountering nuisance conditions, such as algal scums.

Based on the historical Carlson TSI from 2002-present, Cherry Creek Reservoir has been considered eutrophic for Secchi depth and chl α, and ranges between eutrophic and hypereutrophic based on Total Phosphorus concentrations.

Trophic State Classifications and Ranges (May- September)


Useful Links

Depth profile graphic

Trophic State in Cherry Creek Reservoir (2002-2021)

Historic TSI Graph