Missoula Valley Tributary Baseline Nutrient Monitoring

The Missoula Valley is located in Missoula County in Western Montana in the Middle Rockies ecoregion. The Missoula Valley is home to a quickly growing population of approximately 120,000 people. The Clark Fork River flows east to west across the valley; its largest tributary is the Bitterroot River, which flows northwest into the valley and joins the Clark Fork west of the City of Missoula. Missoula’s valley bottom is largely developed with forested land predominating in the headwaters. The people of the valley rely heavily upon its sole-source aquifer which is generally recharged by the Clark Fork River and discharges to both the Bitterroot and Clark Fork rivers depending on the reach and the season. 

With increasing development and impact, it is important to collect and understand the baseline water quality data of the tributaries in the valley.

The Missoula Valley Water Quality District was created by joint resolution between the City of Missoula and the Missoula Board of County Commissioners in 1993.

Mission:  To protect and improve surface and ground water quality within the Missoula Valley.

The Missoula Valley Water Quality District (MVWQD) is charged with protecting and improving the quality of surface water and groundwater within the Missoula Valley. In addition to extensive monitoring of groundwater and the Clark Fork River since the 1990’s, surface water monitoring of the key tributaries to the Clark Fork River is essential to understand the sub-basin pollutant contributions to the Clark Fork, identify baseline conditions in the tributaries as development increases and land subdivisions are requested, and focus on restoration efforts.  

In 2019, the MVWQD initiated a volunteer monitoring program to engage the Missoula Valley community, including its highly skilled water professionals, with the goal of protecting and monitoring the tributaries of the Clark Fork and Bitterroot rivers. This baseline study allows the MVWQD and the community to track the impact that development, climate change, recreation, and historic uses have on the quality of Missoula’s water. To identify how management and land use changes impact water quality, it is necessary to build a quantitative dataset consisting of background nutrient, chloride, and TSS distributions in the valley. This tributary study is a crucial step to meet the water quality improvement goals for the Clark Fork and Bitterroot rivers by focusing on how changes in the sub-basins influence these rivers.   

• To collect baseline data.
• To investigate nutrient loading on tributary streams to the Clark Fork and Bitterroot Rivers in the MVWQD and prioritize water quality improvement projects aimed at reducing nutrients.
• To evaluate chloride and TSS loads and timing as it relates to land use like septic systems or road traction control inputs.

With increasing development and impact, it is important to collect and understand the baseline water quality data of the tributaries in the valley. Although Grant Creek and Miller Creek are the only tributaries currently listed as impaired by DEQ, many of their identified probable sources of impairment, such as streambank modifications/destabilization and site clearance associated with land development, are likely widespread throughout the valley. A baseline water quality assessment and understanding of probable pollution sources to key tributaries is necessary to identify if the MVWQD should focus restoration efforts, work with DEQ to list other streams, or provide specific comments for subdivisions in different basins.    

With the support of the Montana Department of Environmental Quality (DEQ), the MVWQD has monitored six tributaries of the Clark Fork and Bitterroot rivers since 2019: this included Grant Creek, Miller Creek, O’Brien Creek, O’Keefe Creek, Pattee Creek, and Rattlesnake Creek. Beginning in 2021, MVWQD monitored an additional ten tributary streams with the support of Monitoring Montana Waters (MMW), which included Marshall Creek, Donovan Creek, Houle Creek, Mill Creek, Deer Creek, Butler Creek, La Valle Creek, Hayes Creek, Lolo Creek, and Roman Creek. For 2024, MVWQD plans to continue monitoring the original six tributaries funded by DEQ and eight of the original ten tributaries funded by MMW. Due to the proximity of La Valle Creek to Butler creek, MVWQD is alternating between the two streams, monitoring each one every other year. La Valle Creek will be monitored in 2024. Butler Creek will be monitored in 2025. Priority was given to Marshall Creek due to the anticipated development of Marshall Mountain as a public recreational amenity.  

To learn more about the Missoula Valley Water Quality District or Monitoring Montana Waters, click the caption below each organization's logo.