The federal Clean Water Act requires DEQ to assess Montana’s water quality and prepare a report every two years. The Montana Water Quality Report and List of Impaired Waters (known as the Integrated Report) combines reporting information for the Clean Water Act Section 305(b) assessment of water bodies and the Section 303(d) list of water bodies that do not meet water quality standards. Water bodies not meeting standards need pollution reduction studies, called Total Maximum Daily Loads (TMDLs). TMDLs also include plans to improve water quality to eventually meet standards.

When assessing surface water quality in Montana, DEQ is guided by the Beneficial Use Assessment Method for Montana’s Surface Waters. This document describes the framework used to assess state waters and to make the beneficial use support and water quality impairment decisions that are presented in the Water Quality Integrated Report. During the 2020 integrated reporting cycle, DEQ revised this beneficial use assessment method and is requesting public comment on the document.

DEQ assesses whether state surface waters are meeting applicable water quality standards for specific water quality characteristics, or parameters. If a waterbody is not meeting one or more water quality standards, DEQ considers the waterbody impaired and adds it to Montana’s list of impaired waters in the Water Quality Integrated Report. DEQ develops parameter-specific assessment methods which present the required data, analyses, and decision frameworks used to make these parameter-specific impairment listing decisions. During the 2020 integrated reporting cycle, DEQ developed two new parameter-specific assessment methods and is requesting public comment on two documents: Electrical Conductivity (EC) and Sodium Adsorption Ratio (SAR) Assessment Method for Rosebud Creek, the Tongue, Powder, and Little Powder Rivers, and the Tongue River Reservoir and Escherichia coli (E. coli) Assessment Method for State Surface Waters.

Below are links to the Draft 2020 Water Quality Integrated Report for public review.

Final Integrated Reports

These documents and supporting files constitute the State of Montana's FINAL water quality Integrated Report submission to the U.S. EPA for the given reporting cycle. This includes both the Section 303(d) List and Section 305(b) Report as required under the federal Clean Water Act.