Montana StreamStats

Notice Wyoming StreamStats application is now available
Wyoming StreamStats provides basin delineations and basin characteristics for user-selected sites with more capabilities to come in fiscal year 2024.

Notice for drainage area variables used in the National Bankfull Statistics scenario
Base data layers for Montana StreamStats were processed using sinks so that large areas known to be noncontributing are not included in the adjacent contributing areas to watersheds. For this reason, Montana StreamStats uses CONTDA (contributing drainage area) as a variable in most regression equations. The national-scale Bankfull Statistics scenario regression equations were published using DRNAREA (total drainage area) as a variable. Therefore, DRNAREA was added as a variable in Montana StreamStats to allow the Bankfull Statistics scenario to compute, but DRNAREA is set equal to the value of CONTDA and actually represents contributing drainage area.

Regression Equations Based on Channel Width Have Been Added to StreamStats
The U.S. Geological Survey, in cooperation with the Montana Department of Transportation, developed regression equations based on channel-width characteristics to estimate peak-flow frequencies at ungaged sites in Montana. The channel-width regression equations can be used to estimate peak-flow frequencies (peak-flow magnitudes associated with annual exceedance probabilities of 66.7, 50, 42.9, 20, 10, 4, 2, 1, 0.5, and 0.2 percent) at ungaged sites in each of the eight hydrologic regions in Montana. 

The StreamStats interface initially defaults to zero (0) for all channel-width characteristics (active-channel width, bankfull width, remotely sensed width). Users must enter nonzero values for channel widths measured in the field, or from aerial photographs, or both, to use the regression equations for a desired method. Analysts wishing to use only basin characteristics-based regression equations can accept the 0 default and use the resulting basin characteristics-based regression results.

Please refer to the following document for methods, important limitations, and other information regarding channel width regression equations:

• Chase, K.J., Sando, R., Armstrong, D.W., and McCarthy, P., 2021, Regional regression equations based on channel-width characteristics to estimate peak-flow frequencies at ungaged sites in Montana using peak-flow frequency data through water year 2011 (ver. 1.1, September 2021): U.S. Geological Survey Scientific Investigations Report 2020–5142, 49 p., https://doi.org/10.3133/sir20205142.

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:

• Sando, Roy, Sando, S.K., McCarthy, P.M., and Dutton, D.M., 2016, Methods for estimating peak-flow frequencies at ungaged sites in Montana based on data through water year 2011: U.S. Geological Survey Scientific Investigations Report 2015–5019–F, 30 p.

The regression equations for estimating peak-flow frequencies at ungaged sites in the Northwest Hydrologic Region of Montana have been revised. 

• McCarthy, P.M., Sando, Roy, Sando, S.K., and Dutton, D.M., 2016, Methods for estimating streamflow characteristics at ungaged sites in western Montana based on data through water year 2009: U.S. Geological Survey Scientific Investigations Report 2015–5019–G, 19 p.

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.