Science

Report on Statewide Stream Condition Recently Released

Scientists with the Assessment and Monitoring Program in DEC’s Watershed Management Division recently completed a five year long biological assessment of Vermont’s streams and rivers, and a report has been released on the findings of this study. Wadeable stream reaches were randomly selected throughout the State, and surveyed for water chemistry, habitat quality, and macroinvertebrate and fish communities. The health of these biological communities was then assessed on a rating scale from Poor to Excellent based on thresholds in biological criteria established by DEC. Overall results were used to estimate the biological condition of wadeable streams statewide, and to better understand what factors may be causing changes in condition.

The survey found that a vast majority of wadeable stream miles in Vermont meet DEC’s criteria for healthy macroinvertebrate and fish communities, and most streams meet even higher thresholds that are indicative of exceptional water quality. Among sites that did not meet these higher thresholds, the results suggest that stress due to overall land use activities may affect the health of macroinvertebrate communities, which can be susceptible to changes in water chemistry like elevated levels of nutrients and chloride. Fish communities in the survey seem to be more affected by factors like channel erosion and increased temperature, stressors which we expect to be exacerbated by climate change.

The results are consistent with two previous statewide surveys dating back to 2002, though the study design was recently altered to increase our ability to detect trends in future surveys. A comparison to national and regional results from EPA’s National Rivers and Streams Assessment suggests that Vermont is in better condition for chemical stressors, including salinity and nutrients, though fewer Vermont streams were in “least disturbed” condition for phosphorus when compared to other water quality measures. The overall condition of macroinvertebrate and fish communities was also much higher in Vermont compared to EPA’s regional and national results. These findings highlight the unique quality of Vermont’s streams and the importance of DEC’s role in protecting and maintaining the State’s aquatic resources.

For more information on biological monitoring in Vermont’s streams and rivers, visit DEC’s biomonitoring site.