Wyoming StreamStats

StreamStats for Wyoming can be used to estimate streamflow under natural streamflow conditions for the following statistics: 7-day, 2-year low flow (M7D2Y); 7-day, 10-year low flow (M7D10Y); 14-day, 5-year low flow (M14D5Y); 30-day, 5-year low flow (M30D5Y); 60-day, 2-year high flow (V60D2Y); 1-day, 5-year high flow (V1D5Y); 0.1-, 0.2-, 0.5-, 1-, 2-, 4-, 5-, 10-, 20-, 25-, 30-, 50-, 60-, 70-, 75-, 80-, 90-, 95-, 98-, and 99-percent durations for annual streamflows; and 0.1-, 0.5-, 10-, 15-, 20-, 25-, 30-, 40-, 50-, 60-, 70-, 75-, 80-, 85-, 90-, 95-, and 99- percent durations for monthly streamflows for most months. The reports below present the methods used for calculating the respective streamflow statistics at USGS streamgages, and methods used to develop the regression models for estimating the streamflow statistics at ungaged basins using the basin characteristics. 

• Armstrong, D.W., Lange, D.A., and Chase, K.J., 2025, Methods to determine streamflow statistics based on data through water year 2021 for selected streamgages in or near Wyoming: U.S. Geological Survey Scientific Investigations Report 2024–5104, 10 p., https://doi.org/10.3133/sir20245104.
• Taylor, N.J., and Sando, R., 2026, Methods for estimating selected streamflow statistics at ungaged sites in Wyoming based on data through water year 2021: U.S. Geological Survey Scientific Investigations Report 2026–5120, 38 p., https://doi.org/10.3133/sir20265120.

The data releases below contain foundational layers and metadata, and streamgage watershed averages for all basin characteristics used in this study. 

• Hallberg, L.L., Hamilton, W.B., Dutton, D.M., and Brugger, C.L., 2023, Basin Characteristic Datasets for Wyoming StreamStats: U.S. Geological Survey data release, https://doi.org/10.5066/P93JP0VQ.
• Dutton, D.M., Hallberg, L.L., Brown, H.M., and Taylor, N.J., 2025, Delineated watersheds and snapped locations for select streamgages in and near Wyoming: U.S. Geological Survey data release, https://doi.org/10.5066/P1TFBN4M.

Limitations of Regression Equations

The regression equations were developed to estimate selected streamflow statistics for ungaged streams in Wyoming that are unaffected or minimally affected by streamflow alteration. Alteration indices defining the degree of alteration from dams or diversion are available for streamgage basins within Wyoming, but do not comprehensively extend to basins partially contained in neighboring states. Also, the alteration threshold defined by these indices may not be applicable to all basins in Wyoming because water-use data may be incomplete. Streamflow statistics used to develop these regression equations were selected from streamgages classified as unaltered for the period of record analyzed. Therefore, the final regression equations can be used for predicting streamflows at similarly unaltered basins in Wyoming.

Multivariate models, such as these regression equations, may have unreliable results when estimating streamflow statistics for basins with explanatory variables outside the range of values used to develop the equations. The range of explanatory variables for respective regression equations are available in StreamStats.

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