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The StreamStats Program


Flow estimates are now available for Montana!

Beta version 4 is now available for most states on a trial basis, and version 3 remains available. Beta version 4 provides a single user interface (at for all states that are implemented, rather than separate applications for each state, as in versions 2 and 3, and the user interface is more user friendly than previous versions. Flow estimates for user-selected ungaged sites currently cannot be obtained using beta version 4 for the States of Arkansas, Arizona, Georgia, Iowa, Indiana, Maryland, Montana, North Carolina, Oregon, South Carolina, and Tennessee because of unique functionality for those states that is not yet implemented. Users are encouraged to provide comments and report bugs by use of the Help button on the interface, which also provides access to limited beta version 4 documentation. See below for additional information about versions both 3 and 4.

Please contact the StreamStats by email at if you have any questions.

The ability to estimate selected streamflow statistics for ungaged sites was added to Montana StreamStats version 3 on November 10, 2017, but they are not yet available in version 4. Regression equations are available for estimating instantaneous peak flows with annual exceedance probabilities of 66.67, 50, 42.9, 20, 10, 4, 2, 1, 0.5 and 0.2 percent. These peak flows have recurrence intervals of 1.5, 2.33, 2, 5, 10, 25, 50, 100, 200, and 500 years, respectively. In addition, regression equations are available for estimation of low-flow frequencies; mean annual and mean monthly streamflows; and the 20-, 50-, and 80-percent durations for annual and monthly duration streamflows for ungaged sites in western Montana. Regression equations for estimating these statistics are not available for eastern Montana. All equations assume that estimated flows at user-selected sites are unaffected by regulation. The reports below document the available regression equations for Montana, the methods used to develop the equations and to measure the basin characteristics used as explanatory variables in the equations, and the errors associated with the estimates obtained from the equations:


Interactive Map


General information on the Interactive Map application, as well as specific sources and computation methods for basin characteristics are available here.

StreamStats was developed for Montana in cooperation with the Montana Department of Natural Resources and Conservation and the Montana Department of Environmental Quality.

Link to the Montana Department of Natural Resources
Link to the Montana Department of Environmental Quality

Contact Us if you experience any problems with this application.

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