Future Streamflow Estimates for Tongue River to Enable Northern Cheyenne Data Driven Water Management and Planning Active

Atmospheric warming is driving a shift in precipitation from snow to rain, changing precipitation intensity and seasonality, and increasing atmospheric demand for moisture in mountain river watersheds across the western United States. These changes will likely alter the timing and quantity of streamflow in rivers draining from the mountains. The Tongue River flows from the Bighorn mountains in north-central Wyoming into Montana through alpine meadows to sagebrush steppe, prior to its confluence with the Yellowstone River at Miles City, MT. The Tongue River is a little-studied river with hydrologic conditions (e.g. water flow, temperature, quantity) relevant to Tribal water rights and management, fisheries, interstate water rights, irrigation, and reservoir operations. A better understanding of the current and future hydrology of the Tongue River watershed will help Tribal water management professionals make data-driven decisions about how to manage, lease, and utilize their water rights.



This project will use future hydrology estimates (2070-2099) from a previously published database containing two future climate scenarios and 32 different climate models. These data will be used in conjunction with a river system model and input from the Northern Cheyenne Tribe, a project partner, and other area stakeholders to produce estimates and analyses of future streamflow throughout the Tongue River watershed. The river system model will account for irrigation withdrawals and reservoir operations, allowing for future streamflow estimates that include these processes. Project researchers will work with Northern Cheyenne Tribal members and resource managers to ensure that the project analyses are useful for their management objectives.