Wyoming DEQ Releases Water Quality Findings from Bear and Snake River Basins

CHEYENNE, WYOMING – The Wyoming Department of Environmental Quality’s Water Quality Division (WDEQ/WQD) released results from its 2021 probabilistic water quality survey of the Snake and Bear River Basins, revealing that 73% of assessed perennial streams are in “least-disturbed” biological condition. The report highlights that these basins fare better than national estimates (28%), recording far fewer “most-disturbed” streams (18%) compared to 47% nationwide based on the National Rivers and Streams Assessment.

These findings complement the 2021 Tri‑State Bear River Survey, a collaborative companion assessment conducted by Wyoming, Idaho, and Utah to evaluate stream health across the Upper and Central Bear River Basin.

The study identified physical anthropogenic disturbances as the most significant challenges to stream health in the region. Riparian disturbance—characterized by sparse overhanging cover, minimal woody vegetation, bare ground, and bank damage—affects 41% of assessed stream miles, while channel instability impacts 27%. Collected data indicate these alterations impact aquatic life. For example, streams with active channel incision are nine times more likely to have degraded biological condition. These results suggest that maintaining healthy vegetation and stable stream banks is vital for protecting the macroinvertebrate communities that indicate overall aquatic health.

In addition to biological health, the survey evaluated water quality for human consumption and recreation. Results were overwhelmingly positive for drinking water suitability, with 100% of assessed streams meeting the least-disturbed criteria for contaminants such as arsenic, cadmium, lead, and selenium. Recreational water quality was also relatively high, with 77% of streams achieving least-disturbed criteria for Escherichia coli (E. coli). However, regional variations were observed—the Bear River Basin showed higher disturbance, with 33% of streams in most-disturbed biological condition and 42% showing elevated E. coli, compared to more favorable results in the Snake River Basin.

Conducted under WDEQ/WQD’s rotating basin monitoring strategy, this survey helps the state fulfill federal Clean Water Act obligations by providing unbiased estimates of water quality. While not implicating specific streams as impaired, the findings provide a scientific “snapshot” to help prioritize future monitoring and voluntary conservation. By focusing on stressors like bank erosion and riparian health, partners can better target pollutant reduction initiatives to ensure long-term stream health in Wyoming.

Link to Report: Biological Condition of Streams and Rivers in the Bear and Snake River Basins, Wyoming: Results of the 2021 Bear and Snake River Basin Probabilistic Survey

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