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Supplementary resources including documents, reports, frequently asked questions, and guidance. For additional information please visit the specific DEQ program page. To obtain records that are not available on the DEQ website please visit the Public Records Center.

Water Seminar

Water quality is an important topic for all Montanans. DEQ is charged with maintaining and improving clean water in Montana’s rivers, lakes and below the surface—in our groundwater. Montana’s waters are a vital state resource providing recreation, fishing, tourism and drinking water. Our work is complex, scientific and interconnected. 

Learn more about how DEQ works to protect clean water for all Montanans. DEQ created short videos ranging from 1 minute to 30 minutes—most are about 10 minutes—that provide a high-level overview about how water quality protection works in Montana. If you have few minutes of your day, check out the videos. 

Water Seminar - Video Table
Topic Video Link Video Description Website Resources
1. Water Quality Division Welcome Video Link (00:45) Greeting and an introduction from the Water Quality Division Administrator.
2. Water Quality Programs and Governance Video Link (23:07) An integrated approach to addressing water quality; understanding primacy and rulemaking.  Water's Homepage
3. Water Quality Standards Video Link (00:56) The purpose of water quality standards and the difference between numeric and narrative standards. Water's Standards Webpage
4. Beneficial Uses Video Link  (01:23) How beneficial uses of water provide context for protecting water quality. Water's Standards Webpage
5. Setting Standards Video Link (08:09) The process for developing and adopting standards into state rule. Water's Standards Webpage
6. Water Quality Planning Video Link (11:19) The role of monitoring, assessment, TMDLs, and nonpoint source pollution in watershed planning. Water's Total Maximum Daily Load Webpage
7. Nonpoint Source Pollution Video Link (01:12) How voluntary reductions of nonpoint sources of pollution are achieved in Montana. Water's Nonpoint Pollution Webpage
8. Discharge Permitting Video Link (11:26) How information in permit applications are translated into permit limits. Water's Permitting Webpage
9. Nondegradation Video Link (02:31) Applications of Montana’s nondegradation provisions.
10. Public Water Supply Video Link (05:26) What public water supplies are and the regulations that ensure safe drinking water. Water's Drinking Water Webpage
11. Grants and Loans Video Link (09:55) Types of funding available from DEQ for external partners to implement water quality protections. Water's Engineering Infrastructure & Subdivisions Webpage

Water Quality Library

The Water Quality Library was formed to support the mission and operations of the Montana DEQ's Water Quality Division by making water quality documents and publications available to the public. There are over 8,500 titles in the collection including books, reports, journal articles, and DVDs, covering subjects related to water quality including methodology, toxicology, soils, mining, nonpoint pollution, fish, forestry, and modeling.

Search Water Quality Library


Clean Water Act Information Center (CWAIC)

Here you will find information about the quality of Montana's rivers, streams, and lakes in relation to Montana's Water Quality assessments. These assessments are derived from available statewide water monitoring data and information. The Clean Water Act Information Center also provides access to Montana's Water Quality Reports and List of Impaired Surface Waters, as well as online search and mapping tools.

Search Water Quality Assessment Information

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.

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.

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.

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Montana classifies its waterbodies according to present and future beneficial uses they are expected to support (§ 75-5-301, MCA). This layer displays surface water bodies in Montana contained the NHD and their associated use class.

Go To The Use Class Map

Montana’s surface-water-use classification system bases class assignments primarily on water temperature, fish, and associated aquatic life. Each class has an associated beneficial use. A waterbody supports its beneficial uses when it meets the Water Quality Standards (WQS) established to protect those uses. A waterbody is impaired when any one of its WQS are violated.

Determining whether or not a specific use is supported is independent of all other designated uses. For example, a waterbody may partially support aquatic life because of excess nutrients, not support drinking water because of arsenic, but fully support agriculture and industrial uses. Classes A, B, and C are the three most common. Class I is a temporary category assigned to three streams that were grossly impaired when the system was established. Classes A-Closed and A-1 are considered high quality, the principal beneficial use of which is public water supply. The A-Closed class may invoke watershed protection and use restrictions to protect drinking water. Classes B and C each have subsections according to whether they support coldwater or warmwater aquatic life. B-1, B-2, C-1, and C-2 support coldwater aquatic life; B-3 and C-3 support warmwater aquatic life. B and C waters have nearly identical use classifications, but B waters specify drinking water as a beneficial use whereas C waters do not. C-3 streams are suitable for warmwater aquatic life and recreation. Because these streams often contain naturally high total dissolved solids (salinity), their quality is marginal for drinking and agricultural and industrial uses.

In August 2003 Montana added four additional classes: D, E, F, and G. The classes include ephemeral streams (E-1, E-2), ditches (D-1, D-2), seasonal or semi-permanent lakes and ponds (E-3, E-4, E-5), and waters with low or sporadic flow (F-1). G-1 waters must be maintained for watering wildlife and livestock and supporting secondary contact recreation and aquatic life, not including fish. These waters are marginally suitable for irrigation after treatment or with mitigation measures and includes “holding water” from coal bed methane development. Note: The classification system designated uses for waterbodies as present at the time of classification in 1955.

Waterbodies may now have other realized uses that are not officially designated. In such cases, a waterbody may be reclassified to officially recognize these other uses. Conversely, designated uses cannot be removed from a waterbody without a formal Use Attainability Analysis and approval under rulemaking by the Montana Board of Environmental Review. Streams forming the boundary of Indian Reservations are coded as State of Montana (SOM) waters for practical reasons related to enforcing Federal and Montana water quality standards. In some cases meanders, canals, and ditches that transect the boundary and then reconnect with a border stream are also coded as SOM waters even when they are located in part or entirely within the Indian Reservation. As a result of this coding protocol,

If you use the "select by location" procedure to identify streams that are completely within one of the reservations, the resulting selected records may include a small number of streams coded as SOM in the "Authority Entity" field. This is not a mistake and needs to be kept in mind when interpreting selection results. Streams that are not parallel to or located on a border but that cross into and are entirely within an Indian Reservation retain the use class as designated by the ARM description for the watershed they are part of but they are designated as "Not State Jurisdiction" or NSJ in the event table's "Jurisdiction" field and the name of the tribe is recorded in the "Authority Entity" field. The name of the reservation is recorded in the "Area Name" field. Streams that are not parallel to or located on a border but that cross into and are entirely within national parks, wilderness areas or primitive areas are assigned a use class of A-1 as specified by ARM Title 17 Chapter 30 Subchapter 614. The name of the park, primitive area, or wilderness area is recorded in the "Area Name" field of the event table. As a consequence, a stream crossing a border will likely have different use classes on either side of the border.


Statutes, Rules, and Regulations

Circular Titles/Descriptions

  • DEQ 1 - Standards for Water Works
  • DEQ 2 - Design Standards for Wastewater Facilities
  • DEQ 3 - Standards for Non-Community Public Water Systems April 2023 Edition
  • DEQ 4 - Montana Standards for On-Site Subsurface Sewage Treatment Systems April 2023 Edition
  • DEQ 7 - Montana Numeric Water Quality Standards
  • DEQ 8 - Montana Standards for Subdivision Storm Drainage
  • DEQ 10 - Standards for the Development of Springs for Public Water Systems
  • DEQ 12A - Montana Base Numeric Nutrient Standards
  • DEQ 12B - Nutrient Standards Variances
  • DEQ 13 - Montana Policy for Nutrient Trading
  • DEQ 16 - Standards for Hauled Water Cisterns (Water Storage Tanks) for Non-Community Public Systems
  • DEQ 20 - Standards for Nonpublic Water Systems
  • PWS 5 - Groundwater under the Direct Influence of Surface Water
  • PWS 6 - Source Water Protection Delineation
Program/Responsibility DEQ PWS
Coal Bed Methane                    
Discharge Permits                  
Drinking Water Supply          

Facility Design Standards                        
Ground Water Remediation                        
Mixing Zones                      
Water Quality Monitoring                      
Nonpoint Source                    
Source Water Protection                      
TMDL Program                  
Wastewater Systems                      
Water Pollution Control SRF                      
Water/Wastewater Operator Certification                        
National Drinking Water Regulations
Public Water and Sewage Systems
Consumer Confidence Report Rule
Lead and Copper Rule
Disinfectant Byproducts Rule
Montana Chlorination Rule
Surface Water Treatment Rule
Total Coliform Rule
Water Treatment Operators
Drinking Water State Revolving Fund


General Resources

Use EPA's Enforcement and Compliance History Online website to search for facilities in your community to assess their compliance with environmental regulations. You can use ECHO to:

  • Search for Facilities
  • Investigate Pollution Sources
  • Search for EPA Criminal and Civil Enforcement Cases
  • Examine and Create Enforcement-Related Maps
  • Analyze Trends in Compliance and Enforcement Data
  • Explore your State's Performance

Please Note: The data online is provided as a public resource and does not always reflect the most up to date information.

Private water wells and septic systems require homeowners to take more control of their water quality. Well and septic owners have a responsibility to themselves, their families, and their neighbors to protect ground water from contamination and to ensure that water systems provide good quality drinking water.

Stay Well by Checking Your Well

All well owners should conduct an annual water well "check-up" that includes a wellhead and pressure tank inspection. Conducting an annual well check-up of your water system is an important step to take to ensure proper operation of a well. A check-up can prolong your system’s years of service as you monitor water quality.

Annual check-up checklist:

  • At a minimum, test your water for coliform bacteria and nitrates. You can also test for any additional contaminants that may be specific for your area. You should also have your water tested if there is a: change in taste, odor, or appearance; after the well system is serviced; or after a flooding event.
  • Inspect your well parts to ensure they are in good repair. Look for problems such as cracked, corroded, or damaged well casing or settling and cracking of the ground surface around the well casing. If any of these problems are present, your well can become a conduit for contamination to ground water.
  • Check to make sure your well cap is not broken or missing. If your well does not have a sanitary cap (a two-part cap with a rubber seal), it is recommended that you replace it with a sanitary well cap.
  • Inspect your pressure tank and associated plumbing by looking for things like leaks or corrosion, which could lead to future problems.
  • Survey the area around your well to make sure there are no hazardous materials nearby (paint, motor oil, household chemicals, etc.) which could spill and contaminate your well water.

Don’t Wish for Safe Water…Test for It!

What to do After a Flood

Maintaining a Private Septic System