Conservation Spotlight: RiverNET Data & Mill Creek Restoration

A critical component of our RiverNET program is empowering users to use data for conservation. We’d like to shine a spotlight on the the upcoming Mill Creek Restoration project planned by Trout Unlimited. TU is a grassroots organization that seeks to conserve, protect, and restore Montana's incredible cold water fisheries. The project description from TU staff is below:

A degraded stream channel within the Mill Creek project area.

Mill Creek is a major tributary to Yellowstone River with its confluence near the town of Pray, in Paradise Valley of Park County, MT. Of the remaining Yellowstone Cutthroat (YCT) strongholds, Mill Creek is one of the largest watersheds that occurs outside of Yellowstone National Park. Despite its importance to native fish, a legacy of land use has left the lower reaches of Mill Creek in a degraded condition. Approximately 7 miles upstream of its confluence with the Yellowstone River, Mill Creek flows through the 5 Bar 6 Ranch and a section of newly acquired US Forest Service managed land. Previous landowners channelized and diked the north bank, cutting off Mill Creek from its side channels and historic floodplain. The lack of large wood and in-stream habitat complexity within this reach indicates that wood has likely been removed and the stream channel simplified. This area is primarily riffle habitat with a small number of pools that have limited fish-holding capabilities. However, this stretch of river is an important spawning and rearing area for migratory Yellowstone Cutthroat Trout because it occurs upstream of an irrigation diversion that is responsible for the annual dewatering of lower Mill Creek. The project will include floodplain reconnection and the installation of log structures to promote gravel recruitment and pool development. The completed project will improve spawning and rearing habitat for YCT and restore natural processes that promote floodplain reconnection, the establishment of riparian plants, and recharge the local aquifer. The first phase of Mill Creek restoration is planned for fall 2022.

The hydrograph below is from a RiverNET sensor station Mill Creek, with lines representing discharge data from our Upper Mill Ck, East Fork Mill Ck, and Lower Mill Ck sensor stations. The Upper and East Fork stations are upstream of TU's restoration project location while the Lower station is downstream of the project location. Our hydrograph indicates that the discharge in Mill Creek significantly decreases during the summer months to levels below natural base flow. By restoring the flood plain with this restoration project, TU will help to increase the amount of water stored in the aquifer. This is because high waters during peak flow will now be able to access the natural flood plain and seep into the ground. This will be essential to help to sustain base flow in Mill Creek throughout the summer as groundwater is a key contributor to summer flows as the snow pack is depleted. We believe our future RiverNET data will reflect the positive impacts of this restoration project with increased discharge during summer months at our sensor stations downstream of the project area. Click here to support RiverNET!