Water Quality Trends

Project Summary

Water Quality Trends

Biotic Index
Dissolved Oxygen
Fecal Coliform Bacteria
Nitrate Nitrogen
Total Phosphorus

Water Quality Trends
Biotic Index

The biotic index is an indicator of stream water quality by an analysis of the macroinvertebrate community that is present. The biotic index measures the sensitivity of the benthic community to organic pollutants such as sewage and other oxygen-demanding substances. Different macroinvertebrates have varying levels of tolerance or intolerance to pollution. The biotic index assigns tolerance values to each taxon (group) and then computes an average value for the community (all organisms collected or subset). Biotic index values range from 0 to 10, with lower values from 0 to 3.5 indicitive of no apparent organic pollution and values greater than 5.5 suggesting significant levels of organic pollutants.

The following graphs present county-wide trends in the biotic index for each year that data were collected. High color values may exceed the maximum shown on the legend.

View Station Location Map | View Animated Graphic
1991	1992	1993
1994	1995	1996
1997	1998	1999
2000	2001