Estimating Future Streamflow in Eastern Montana Using the Precipitation-Runoff Modeling System and the RegCM3 Regional Climate Model

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Streams in the Northern Great Plains provide critical “green lines” of habitat for aquatic and terrestrial wildlife. However, changes in water quantity associated with global climate change may transform some prairie streams from essential refuges to habitats no longer capable of supporting fishes. Although studies have examined climate change effects on larger river basins across the United States, including the Upper Missouri and Yellowstone Rivers, very little information is available concerning the future of smaller streams in eastern Montana and the Northern Great Plains. Therefore, U.S. Geological Survey (USGS) researchers and their partners are investigating effects of climate change on streamflow in smaller streams in eastern Montana. The streamflow information is being used by fisheries biologists to estimate effects of climate change on fish populations in the Northern Great Plains.

Cows by a stream.

The Precipitation-Runoff Modeling System (PRMS) loosely coupled with the RegCM3 regional climate model is being used to estimate changes in streamflow under future climate scenarios in eastern Montana. PRMS is a deterministic, distributed-parameter, process-based model that simulates the effects of precipitation, temperature, and land use on streamflow. RegCM3 is used to dynamically downscale global climate simulations. Specific methods include:

  • Simulating daily streamflow for baseline conditions for seven watersheds in Montana using PRMS and daily Daymet precipitation and minimum and maximum air temperature. The Daymet data set (available at http://daymet.ornl.gov) provides gridded (1–kilometer resolution) estimates of daily weather parameters for North America.
  • Simulating future daily streamflows for the seven watersheds using PRMS and projected changes in daily precipitation and minimum and maximum air temperature from the RegCM3 regional climate model. RegCM3 (available at http://regclim.coas.oregonstate.edu) uses lateral boundary conditions from selected General Circulation Models (GCMs), and then simulates atmospheric circulation and surface interactions internally at a 15-kilometer resolution.
  • Using projected climate conditions to predict where changes in fish assemblages will occur, relative to the current levels of fish biodiversity and biological integrity (Index of Biotic Integrity or IBI) for the ~1,500 samples in a regional fish database. This will allow researchers to identify areas of primary conservation concern and compare them to the areas that are most likely to undergo changes as a result of climate change.
Map of Estimating Future Streamflow in Eastern Montana

In addition to the PRMS modeling, USGS hydrologists installed flow-monitoring equipment in streams in the O’Fallon Creek and Redwater River watersheds. They also measured streamflow and water levels in groundwater pools. The data will help researchers understand stream flow variability in the pools and channels of these intermittent prairie streams.

 

Management Benefits

Fisheries and resource managers will be provided with information regarding current and potential future conditions of prairie stream ecosystems. This information can be used to help focus conservation and restoration efforts in the northern Great Plains. Information related to changes in timing and quantities of streamflow will be useful to agencies and stakeholders, such as watershed conservation groups, ranchers, and others that rely on, or work near prairie streams. This project is also providing information to help preserve prairie fish species and their habitat, ultimately benefiting the entire prairie ecosystem and the communities in the northern Great Plains.

 

This project was funded by the Plains and Prairie Potholes Landscape Conservation Cooperative and the Bureau of Land Management.