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.
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.
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: