Main Page          Monitoring and Assessment          TMDL Development          Restoration and Protection

Wetlands          Outreach          Contact Information

Project Purpose

The state of Montana monitors its waters and conducts water quality assessments to determine if waterbodies are supporting their designated uses. Waters that are determined not to be supporting their designated uses are called impaired and are placed on Montana’s list of impaired waters. Impaired waterbodies and their associated probable causes and sources of impairment are published within Montana’s biennial Water Quality Integrated Report.

Montana’s state law, and the federal Clean Water Act that was established by Congress in 1972, require development of total maximum daily loads (TMDLs) for all waterbodies impaired by a pollutant (e.g., metals, nutrients, sediment, temperature, etc.). A TMDL is the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards (think of a TMDL as a loading rate). TMDL development includes four main steps:

• Characterizing the impaired waterbody’s existing water quality conditions and comparing those conditions to Montana’s water quality standards. During this step, measurable target values are set to help evaluate the stream’s condition in relation to the applicable water quality standards.

• Quantifying the magnitude of the pollutant contribution from each significant source

• Determining the total allowable load of the pollutant to the waterbody (the TMDL)

• Allocating the total allowable pollutant load into individual loads for each significant source (referred to as load allocations for nonpoint sources and wasteload allocations for point sources)

The TMDL planning process for this project incorporates a combination of water quality sampling and hydrologic modeling to further identify and quantify metals, nutrient, sediment, and temperature contributions from all significant sources to the streams identified in the table below. For more information about the development of TMDLs, please see the What is a TMDL? page on this site or download our pamphlet: Understanding the TMDL Process.

Project Contacts