Beneficial Use Assessment

DEQ’s Water Quality Monitoring and Assessment Section assesses whether state waters meet water quality standards and support beneficial uses. Beneficial use assessment is one step in the water quality planning process; it requires monitoring and informs Total Maximum Daily Loads (TMDLs) and water quality protection and restoration.

Beneficial use assessment of Montana's rivers, streams, and lakes is tied to goals of the federal Clean Water Act and the Montana Water Quality Act which require states to:

  • Assign designated uses to waters and develop water quality standards to protect those uses;
  • Monitor and assess water quality;
  • List impaired waters that do not meet standards;
  • Identify pollutant sources and set pollutant-reduction goals needed to achieve standards.

DEQ uses available data to assess water quality based on established water quality standards and reports on the status and trends of water quality every two years in Montana’s Water Quality Report and List of Impaired Surface Waters.