Biotic Indices

A number of water quality indices have been based on the tolerance of stream insects to varying water chemistry. Below are two of the most commmonly used biotic indicies.

This index uses tolerance numbers assigned to the families present in a stream to assign a quantifiable number to the water quality.
This index estimates water quality by counting the number of families observed from pollution sensitive orders: Ephemeroptera, Plecoptera, and Tricoptera (EPT).