Montana Department of Environmental Quality About Us Permitting & Operator Assistance Public Participation


Program Overview

Water quality standards consist of several parts:

  • Beneficial uses — Identify how people, aquatic communities, and wildlife use our waters
  • Numeric standards — Amounts of specific pollutants allowed in a body of water and still protects it for the beneficial uses
  • Narrative standards — Statements of unacceptable conditions in and on the water
  • Nondegradation protections — Extra protection for high-quality or unique waters and existing uses

Together, the beneficial uses, numeric and narrative standards, and nondegration protections provide the framework for achieving Federal Clean Water Act and Montana Water Quality Act goals and protecting Montana water resources.

For more information: Montana Code Annotated (MCA 75-5) Water Quality Classification & Standards

Standards Contacts

Water Quality Standards and Modeling Section Supervisor
Katie Makarowski (406) 444-3507

Water Quality Standards Scientist
Rosie Sada De Suplee (406) 444-5964

Water Quality Standards Scientist 
Lauren Sweeney (406) 444-5226

Water Quality Standards Scientist
Mike Suplee (406) 444-0831

Water Quality Modeler
Eric Regensburger (406) 444-6714

Water Quality Standards Scientist
Christy Meredith (406) 444-0371

Why Water Quality Standards

  • Protect water resources for uses such as fishing, swimming and other recreation, and sustaining fish, bugs, plants, and other aquatic life
  • Are a measure to identify polluted waters or healthy waters in need of protection
  • Guide the limits set on what regulated facilities can discharge to surface water

The federal Clean Water Act requires states to designate beneficial uses for all waters and develop water quality standards to protect each use.

States either develop their own criteria or implement federal criteria for evaluating water quality. These criteria must accurately reflect the latest scientific knowledge. They are based solely on data and scientific judgments about pollutant concentrations and their effects on the environment, aquatic life, and human health. Montana water quality criteria include both numeric and narrative criteria. Water quality criteria for each use class are detailed in the Montana Code Annotated. Additionally, a detailed map of Montana's use classes can be found HERE. (Please note that this map is data intensive, for mobile user or slow internet connections a pdf map is provided HERE) (Note: Montana does not designate use classes for Tribal Nations). Additionally, a map detailing Montana’s Outstanding Resource Waters can be found HERE.

Numeric Criteria

Most of Montana’s water quality criteria are numeric; that is, the criteria define precise, measurable concentrations of pollutants that if exceeded would harm the use. Montana’s numeric water quality criteria are published in Circular DEQ-7 and Circular DEQ-12A.

Montana also has Nutrient Standards Variances which are published in Circular DEQ-12B.

Narrative Criteria

Some pollutants have narrative water quality criteria, which are statements (instead of specific quantities) that describe the desired water quality condition in terms of allowable ranges and maximums (e.g., water pH and temperature) or in terms of specific variation from natural conditions (e.g., water turbidity and color). Each use class defined in the rule has narrative criteria, and some narratives define an allowable change from naturally-occurring conditions. Naturally-occurring conditions are determined by reviewing historical data for a waterbody, if available, or by comparing conditions with a reference waterbody, an unaltered or otherwise in its most natural condition.

Montana’s water quality standards and details of how water quality standards are implemented in point-source discharge permitting are contained in Montana Administrative Rules. All current state water rules and Montana water quality standards are available on the Water Quality Regulations and Forms page.


Nondegradation protections maintain high quality waters from deterioration. Montana’s Nondegradation policy provides three levels of protection for surface waters:

  1. Existing uses of the water body must be maintained and protected.
  2. High water quality (water quality better than the applicable water quality standard) must be maintained unless a lowering of water quality is necessary to accommodate important economic and social development.
  3. Exceptional characteristics of specific waters designated as outstanding, very sensitive, or unique resources -- called outstanding resource value water -- must be maintained and protected.

The Montana Water Quality Act and Federal Clean Water Act require the State of Montana at least every three years to review and, as appropriate, modify adopted standards of water quality. On May 12, 2023, the DEQ opened a public comment period and will hold a public hearing on June 28, 2023, for the purpose of reviewing Montana’s water quality standards. All interested persons are invited to submit data, views, or arguments concerning water quality standards orally or in writing. Comments should identify the water quality standard at issue, any suggested revision to the standard, and the basis for the suggested revision, including technical information.

On June 28, 2023, the Department will hold a public hearing to hear comments on water quality standards at 11:00 am in room 111 of the Metcalf Building at 1520 E 6th Avenue, Helena, Montana. More information, including instructions for attending the public hearing remotely via Zoom, is available at Data, views, or arguments may be submitted in writing no later than 5:00 pm on June 28, 2023, online at, by email to, or by mail to DEQ Water Quality Division, Water Quality Planning Bureau, P.O. Box 200901, Helena, Montana, 59620-0901. 

Background:  On December 11, 2020 the Board of Environmental Review (board), voted to adopt the Department of Environmental Quality’s (department) proposed selenium water quality standard for Lake Koocanusa into state law and determined the proposed standard was no more stringent than federal guidelines. Therefore, there was no requirement for the completion of written findings as described in MCA 75-5-203. The multi-part standard includes fish tissue and water column components with the following numeric values: 15.1 mg/kg dry weight (dw) egg/ovary, 11.3 mg/kg dw muscle, 8.5 mg/kg dw whole body, and 0.8 μg/L total dissolved selenium in Lake Koocanusa and 3.1 μg/L in the Kootenai River mainstem. See ARM 17.30.632. The frequency and duration of the fish tissue standards are instantaneous measurements, not to be exceeded. The water column standard is computed as a 30-day average and shall not be exceeded more than once in three years, on average.

The standards were adopted into state law on December 25, 2020 and codified in ARM 17.30.632. The water quality standards were approved by the U.S. Environmental Protection Agency (EPA) on February 25, 2021. Two petitions were filed to the board calling for a review of the stringency determination for the site-specific water column standard for Lake Koocanusa in ARM 17.30.632(7)(a). On February 25, 2022 the board reversed its previous stringency determination and determined that the site-specific water column standard for Lake Koocanusa is more stringent than comparable federal guidelines. The department, therefore, complied with MCA 75-5-203 by making the written findings set forth in 75-5-203(2), MCA. 

Associated Materials:

Lake Koocanusa Selenium Updates:

 Items Related to 2020 Rulemaking:

Copies of any of these documents may also be obtained by contacting Lauren Sweeney at (406) 444-5226 or

The Department of Environmental Quality continues to work with the British Columbia Ministry of Environment and Climate Change Strategy (BC-ENV) and the Lake Koocanusa Monitoring and Research Working Group (LKMRWG). The LKMRWG is a bi-national, multi-stakeholder work group comprised of three committees; Steering Committee, Monitoring and Research Committee (MRC), and the Selenium Technical Subcommittee (SeTSC). The department and BC-ENV co-manage a wiki website for items related to the LKRMWG including; meeting agendas, meeting summaries, data, literature, technical reports, sampling and analysis plans, and more. Lake Koocanusa Wiki Site

Rulemaking Background: In 2021 the 67th Montana Legislature enacted Senate Bill 358 (codified at 75-5-321, MCA).  Senate Bill 358 requires the department to adopt rules related to narrative nutrient standards in consultation with the advisory nutrient work group.  Nutrients, in this context, refer to total phosphorus and total nitrogen concentrations in state surface waters.  The rules are required to provide for the development of an adaptive management program which allows for an incremental watershed approach for protecting and maintaining water quality. The department convened the nutrient work group in May 2021 and held meetings approximately bimonthly through the end of October 2021 to adopt a comprehensive rule package related to narrative nutrient standards. Despite a concerted effort by the department and the nutrient work group to develop a comprehensive rule package, there remains a substantial amount of work needed for the department to fully address the concerns of multiple parties. Rather than immediately move forward with a comprehensive rule package, the department has opted to adopt New Rule I, which establishes the basic elements of an adaptive management program per Senate Bill 358.  Proposed New Rule I provides a framework for the department to follow as it continues to meet and consult with the nutrient work group and work toward completion of the comprehensive rule package, to be adopted later in 2022.

Opportunity to Comment:  On February 8, 2022, at 2:00 p.m., the department will hold a public hearing in Room 111 of the Metcalf Building, 1520 East Sixth Avenue, Helena, Montana, to consider the proposed amendments and adoption of the New Rule I.  The department is committed to preventing the spread of COVID-19 and promoting the health and wellness of others.  Members of the public may participate either in-person or virtually.  For in-person meetings, while face masks are not required, meeting attendees are welcome to wear masks.  If you are not feeling well, please do not attend the in-person meeting.  Information on how to attend the hearing remotely via Zoom is provided in the link to MAR Notice No. 17-420 provided below:

Additional information about the rulemaking can also be obtained by contacting Michael Suplee, PhD at