StreamStats in Montana and Yellowstone River Basin in Wyoming

The ability to estimate selected streamflow statistics for ungaged sites was added to Montana StreamStats November 10, 2017. 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:

The regression equations for estimating peak-flow frequencies at ungaged sites in the Northwest Hydrologic Region of Montana are being revised. The StreamStats application for Montana has disabled the peak-flow frequency estimates in the Northwest Hydrlogic Region until the equations and report are revised.  

StreamStats also can provide basin delineations and basin characteristics for user-selected sites in the Yellowstone River Basin in Wyoming. This part of Wyoming was implemented as part of the effort to implement Montana. To obtain basin delineations and basin characteristics in this area of Wyoming, users should select Montana as the State. After making this selection, the map will redraw showing hatching over the entire State of Wyoming; however, the stream grid will appear at zoom level 15 or greater and delineations can be obtained.

Click on this link to obtain general information on the Montana application, as well as specific sources and computation methods for basin characteristics. 

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