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Welcome to StreamStats


Beta version 4 has arrived!

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. Information for user-selected ungaged sites currently cannot be obtained using beta version 4 for the States of Iowa, Indiana, North Carolina, and Oregon 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.

StreamStats is implemented for all of Colorado. This application implements regression equations for estimating instantaneous peak flows with probabilities of occurring in any given year of 50, 20, 10, 4, 2, 1, 0.5, and 0.2 percent. These statistics also are referred to as the 2-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year floods. New peak-flow equations were made available in version 3 for eastern Colorado on Nov. 23, 2016, but they are not yet available in version 4. StreamStats also implements regression equations for estimating annual mean flows, mean flows for each month, the flows exceeded 10, 25, 50, 75, and 90 percent of the time, 7-day minimum flows with recurrence intervals of 2, 10, and 50 years, and 7-day maximum flows with recurrence intervals of 2, 10, and 50 years. These non-peak-flow equations are not applicable to the Plains region, which comprises approximately the eastern half of Colorado. The equations in Colorado StreamStats are documented in the reports:

In addition to presentation of the equations, the report also describes the errors associated with the estimates obtained from the equations, the methods used to develop the equations, and the methods used to compute the basin characteristics included as explanatory variables in the equations. StreamStats users should familiarize themselves with the report before attempting to obtain estimates of streamflow statistics for ungaged sites. Application of the equations to ungaged sites assumes that flows at the sites occur under natural conditions. The equations in the above report supersede previous equations that were published in 1985 and 2000 by the U.S. Geological Survey.


Interactive Map



Prior to June 2, 2014, the Prediction Errors (standard errors of predication, in percent) reported for mean annual and monthly flows and for flow-durations in the outputs from the Estimate Flows using Regression Equations tool in StreamStats were erroneous. The reported prediction errors generally were smaller than the actual values. The errors in StreamStats outputs were the result of errors in the formulas originally used by Capesius and Stephens, 2009, to compute the error terms. As a result, the report was revised, and a notice of errata that describes the nature of the errors and corrections was released on April 25, 2014. The notice of errata is on-line at Note that only the prediction errors were erroneous. All flow estimates presented by StreamStats were correct.

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

StreamStats for Colorado was developed in cooperation with the Colorado Department of Transportation and the Colorado Water Conservation Board.

Link to the CO Department of Transportation
Link to the CO Water Conservation Board

Contact Us if you experience any problems with this application.

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