Monitoring & Assessment

Under the Clean Water Act, all surface waters are designated with specific beneficial uses that they should be capable of supporting. Beneficial uses are the various ways a waterbody can be used, including:

• Drinking, culinary and food processing;
• Bathing, swimming and recreation;
• Growth and propagation of salmonid or non-salmonid fishes and associated aquatic life, waterfowl, and furbearers;
• Agricultural water supply;
• Industrial water supply.

Water quality standards specify maximum allowable levels of alteration during use of state waters (Mohr, 2012). Water quality standards are established to protect designated beneficial uses; the standards describe the desired condition of a waterbody and are the benchmarks to aim for in protecting and maintaining water quality.

Water quality standards consist of designated uses, criteria to protect designated uses, and nondegradation requirements to protect existing uses and high-quality waters. Water quality criteria can be numeric (e.g., the maximum pollutant concentration allowed in a waterbody) or narrative (e.g., a criteria that describes the desired conditions of a water body being “free from” certain negative conditions, or “no increases are allowed above naturally occurring concentrations”).

DEQ monitors and assesses state waters to identify waterbodies or waterbody segments, also known as assessment units, that are threatened or impaired (MCA 75-5-702). A waterbody is considered “impaired” if it fails to meet one or more water quality standard. Impaired waters do not fully support all their designated beneficial uses. Montana’s Water Quality Integrated Report contains the list of impaired waters. Impaired waters remain on the list until there is sufficient credible data to remove them, and causes of impairment carry over from each biennial reporting cycle until they are removed.

Section 303(d) of the Federal Clean Water Act requires each state to develop a list of waters that do not meet water quality standards. The 303(d) list is a subset of Montana’s impaired waters list; waterbodies on the 303(d) list have at least one impairment caused by a pollutant for which a TMDL needs to be developed, and they are not expected to meet water quality standards even after technology-based controls for point sources or other control requirements such as Best Management Practices (BMPs) for nonpoint sources. States are required to submit their 303(d) lists to EPA every other year.

Pollution is the man-made or human-induced alteration of the chemical, physical, biological, and radiological integrity of water that has a harmful effect on any living thing that drinks or uses or lives in it. Pollution may be from a point source, a single identifiable source from which pollutants are discharged such as a pipe. Pollution may also be from nonpoint sources which are typically diffuse and include all forms of pollution not regulated by a discharge permit under the Montana Pollutant Discharge Elimination System.

Pollutants are a category of pollution. A pollutant is any substance that is introduced into a water resource, naturally or by human activities, that adversely affects the water quality for a specific use. Pollutant causes of impairment include heavy metals, sediment, nitrogen, phosphorus, E. coli, salinity, pesticides, polychlorinated biphenyls (PCBs), and many others. For each waterbody-pollutant combination that appears on the 303(d) list, a Total Maximum Daily Load (TMDL) study must be developed to identify the maximum amount of a pollutant a waterbody can receive and still meet water quality standards. Non-pollutant causes of impairment for which TMDLs are not needed include habitat alterations, flow alterations, etc.

The goal of beneficial use assessment is to use the best available data and science to assess the condition of Montana’s surface waters and support water quality protection and improvement.

Assessment Priorities

DEQ progresses throughout the state to assess waterbodies or waterbody segments that haven’t been already or recently assessed. Often, DEQ assesses multiple waterbodies within a watershed following a watershed approach, and evaluates multiple types of pollution at once. Assessments are often completed in watersheds where Total Maximum Daily Loads (TMDLs) have not already been completed

Assessments identify probable causes and sources of impairment and inform stakeholders interested in implementing activities to protect and improve water quality. Removal of impairments from the list of impaired waters is a common end goal of restoration and assessments can help track or confirm water quality improvements.

Data Collection and Call for Data

DEQ collects chemical, biological and physical parameters for waterbodies conforming to data quality requirements specified in DEQ’s beneficial use assessment methods. Monitoring for beneficial use assessment purposes aims to identify probable causes and sources of pollution. DEQ can only assess water quality and modify the list of impaired waters if there is sufficient credible data.

During beneficial use assessment, DEQ compiles and reviews all currently available data, including that obtained from federal, state, and local agencies, private entities, or individuals with an interest in water quality protection. Every two years, DEQ releases a “call for data” in which people are invited to submit data to DEQ for consideration during assessment.

Assessment Methods

DEQ evaluates data to ensure it meets data quality requirements specified in DEQ’s beneficial use assessment methods. DEQ then uses these same methods to analyze the data and decide whether a waterbody is impaired or not. Assessment methods are dynamic and change as new information and assessment techniques become available. Periodic updates aim to result in more accurate and reliable assessment decisions. Montana’s beneficial use assessment methods include:

• Beneficial Use Assessment (PDF)
• Nutrients for Wadeable Streams (PDF)
• Metals (PDF)
• Sediment in Mountainous Streams (PDF)
• E. coli (PDF)
• EC and SAR in Rosebud Cr, Tongue, Powder and Little Powder R., and Tongue Res. (PDF)
• Responses to public comment on EC/SAR Draft (PDF)
• Sulfate Guidance
• Nitrate Guidance (PDF)