Western Mountains Ecoregion - National Rivers and Streams Assessment Results

• In the Western Mountains ecoregion, biological condition was good in 61% of river and stream miles based on  benthic macroinvertebrates. 
• The most widespread stressors assessed in the Western Mountains region were phosphorus with 25% of river and stream miles in poor condition; and nitrogen, in-stream fish habitat, and streambed sediments each with 17% of miles in poor condition.     
• Cyanobacteria are photosynthetic microorganisms that  occur at low levels. Under the right conditions (elevated nutrients and increasing temperature), cyanobacteria can grow at elevated rates producing blooms. Not all cyanobacterial blooms are toxic, but some may release toxins, such as microcystins. For information about risks at specific locations, recreational water users should check with state, tribal or local governments.
  • Microcystins detections occurred in 1% of river and stream miles and no miles were above EPA’s criterion recommendation in the Western Mountain ecoregion.

South Saint Vrain Creek, CO

Change from 2013-14*

• The percent of river and stream miles in good condition for phosphorus increased by 23 percentage points between 2013-14 and 2018-19 in the Western Mountains.
• The percent of river and stream miles with microcystin detections decreased by 31 percentage points.

To access more ecoregional specific information, please visit the interactive NRSA Dashboard.

* The change analysis is based on information from two points in time – 2013-14 and 2018-19.