Water Quality Data and Assessment TMDL Development
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Water Quality Monitoring and Assessment in Montana
Montana DEQ performs water quality assessments to determine whether a waterbody is impaired. An impairment means that the waterbody is not meeting Montana's water quality standards for the pollutant being assessed (e.g., iron, salinity, sediment, temperature) because one or more of the waterbody's water quality beneficial uses (support of: agricultural uses, aquatic life, human recreation, and/or drinking water) are limited or harmed to some extent. Waterbodies that have been monitored by DEQ are also referred to as "assessment units." Assessment units can be the full length of a stream or the full extent of a lake or reservoir, or they may be a portion of a lake or stream (a stream segment). Montana DEQ may choose to break streams into multiple segments, determined by a variety of factors, such as stream length for very long streams. The Montana portion of the Tongue River is divided into seven waterbody segments, or assessment units (see table below).
Tongue River Watershed Water Quality Assessment Information
The table below contains all of the waterbodies in the Montana portion of the Tongue River watershed that have been assessed by Montana DEQ, and lists the pollutants for which the waterbody was determined to be impaired. Not all waterbodies in the Tongue River watershed have been sampled/monitored; therefore, we do not know whether their water quality beneficial uses are being fully supported and if they are meeting Montana's water quality standards. However, water quality monitoring has been conducted on additional tributaries of the Tongue River not shown in the below table, but DEQ has insufficient data to assess whether they meet water quality standards.
See Montana DEQ's Clean Water Act Information Center to view summaries of water quality impairments and full assessment reports.
Waterbody Segment (Assessment Unit)
|
Assessment Unit ID
|
County
|
Probable Impairment Causes (2020)1
|
Tongue River
|
Tongue River
Wyoming border to Wyoming border
|
MT42B001_011
|
Big Horn
|
None identified
|
Tongue River
Wyoming border to Tongue River Reservoir
|
MT42B001_010
|
Big Horn
|
Iron
Flow regime modification
|
Tongue River
Tongue River Dam to Prairie Dog Creek
|
MT42B001_020
|
Big Horn,
Rosebud
|
Flow regime modification
|
Tongue River
Prairie Dog Creek to Hanging Woman Creek
|
MT42B001_021
|
Rosebud
|
Flow regime modification
|
Tongue River
Hanging Woman Creek to Beaver Creek
|
MT42C001_013
|
Rosebud
|
Iron
Flow regime modifications
Sediment
|
Tongue River
Beaver Creek to Twelve Mile Dam, T6N, R48E, S29
|
MT42C001_014
|
Rosebud,
Custer
|
Iron
Flow regime modifications
Sediment
Specific Conductivity
|
Tongue River
Twelve Mile Dam to mouth (Yellowstone River)
|
MT42C001_011
|
Custer
|
Cadmium
Copper
Iron
Lead
Flow regime modification
Nickel
Salinity
Sediment
Zinc
|
Tongue River Reservoir
|
Tongue River Reservoir
|
MT42B003_010
|
Big Horn
|
Chlorophyll-a
Dissolved oxygen
Sediment
|
Tongue River Tributaries
|
Hanging Woman Creek
Wyoming border to Stroud Creek
|
MT42B002_032
|
Big Horn,
Rosebud
|
Salinity
Flow regime modification
|
Hanging Woman Creek
Stroud Creek to mouth (Tongue River)
|
MT42B002_031
|
Rosebud
|
Iron
Salinity
Sedimentation-Siltation
Flow regime modification
|
Otter Creek
Headwaters to mouth (Tongue River)
|
MT42C002_020
|
Powder River,
Rosebud
|
Iron
Salinity
Alteration in streamside or littoral vegetative covers
|
Pumpkin Creek
Headwaters to Little Pumpkin Creek
|
MT42C002_061
|
Powder River
|
Salinity
Temperature
Flow regime modification
|
Pumpkin Creek
Little Pumpkin Creek to the mouth (Tongue River)
|
MT42C002_062
|
Powder River,
Custer
|
Salinity
Temperature
Flow regime modification
|
1 Impairment causes identified in Montana’s 2020 Water Quality Integrated Report
|
New Assessments Taking Place in the Tongue River Watershed
In 2019, Montana DEQ re-assessed the segment of the Tongue River between Beaver Creek and the Twelve Mile Dam (assessment unit MT42C001_014) to determine whether it is impaired for salinity, and has listed this segment as impaired for specific conductivity on the 2020 list of impaired waters.
Montana's assessment method for electrical conductivity (EC) and sodium adsorption ratio (SAR) can be found on DEQ's Monitoring and Assessment webpage under the "Beneficial Use Assessment" accordion. EC and SAR water quality standards for the Tongue River can be viewed on the Tongue River Water Quality Standards page.
Data Used for Salinity Assessments and in the Tongue River Water Quality Model
All of the water quality and flow data used by Montana DEQ is available in either the National Water Quality Portal that is maintained by the U.S. Environmental Protection Agency, or the U.S. Geological Survey's (USGS) NWIS database for Montana. The National Water Quality Portal contains data collected by Montana DEQ, volunteer monitoring groups, the U.S. Geological Survey (USGS), as well as other data collection entities. The USGS's Water Quality Data for Montana website (NWIS) provides data downloads for both daily flow and water quality data collected at USGS gages and for laboratory-analyzed samples collected by the USGS.
Additional information on the sources of data being used for the Tongue River salinity water quality model is contained on the Salinity Model page.
Tongue River Project Contacts
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Page Released: July 6, 2016
Last Updated: May 24, 2023