Contact: Mary Anne Nelson, Surface & Wastewater Division Administrator, mary.anne.nelson@deq.idaho.gov
CHEYENNE, Wyo. — The Wyoming, Idaho, and Utah Departments of Environmental Quality have announced the results of the 2021 Tri-State Bear Survey (TBS), a water quality assessment of perennial streams and rivers within the Upper and Central Bear River Basin. This collaborative effort leveraged a probabilistic survey design to provide a statistically unbiased representation of the basin’s stream ecological health across state lines. By monitoring benthic macroinvertebrates and various physicochemical parameters, the study establishes a vital baseline for the Bear River Commission’s Water Quality Committee to track long-term trends and fulfill federal Clean Water Act obligations.
The survey findings indicate that the Bear River Basin maintains relatively favorable biological conditions compared to national averages, with 37% of perennial stream miles classified as “least disturbed.” Chemical stressors such as total nitrogen and total phosphorus were found to be less prevalent in the study area than reported in EPA’s most recent National Rivers and Streams Assessment. Additionally, most sites tested in Wyoming and Idaho met safety thresholds for drinking water suitability and human health, though the study did identify 13 sites that exceeded a study-specific single-sample threshold for E. coli, an indicator bacterium for assessing fecal contamination in water.
While chemical water quality remains a strength of the basin, the report identifies physical habitat alteration as the primary challenge facing the basin. Riparian disturbance and channel instability were documented as the most extensive physical stressors, affecting 42% and 34% of stream miles, respectively. These physical stressors, often characterized by minimal woody vegetation, direct bank disturbance, accelerated bank erosion, and excess sediment, are most likely to impact biological communities. Results of the TBS will guide future conservation strategies and pollutant reduction efforts to protect the basin’s highly valued ecosystem services.