Streamflow statistics are periodically computed by the USGS for data collected at streamflow-gaging stations and partial-record stations. Common streamflow statistics include streamflow frequency (such as the 100-year recurrence interval peak streamflow, or 100-year flood) and flow-duration statistics (such as the 98-percent duration flow). Streamflow statistics are used to develop methods to estimate streamflow at ungaged sites where physical and climatic characteristics of the sites' drainage basins are known.
The streamflow statistics for gaged sites are regressed against basin characteristics for the gaged sites in a generalized least-squares regression analysis to develop equations for estimation of streamflow at ungaged sites.
The most recent analysis of streamflow statistics for Alaska and conterminous basins in Canada is presented in two reports completed in 2003. The state was divided into seven streamflow analysis regions for the analyses. Annual high-flow statistics and monthly and seasonal low-flow statistics presented in USGS Water-Resources Investigative Report 03-4114 are:
- Annual high-duration streamflow statistics
- 15-, 10-, 9-, 8-, 7-, 6-, 5-, 4-, 3-, 2-, 1-percent duration flows for the October-September water year for all seven regions
- Monthly low-duration streamflow statistics
- 98-, 95-, 90-, 85-, 80-, 70-, 60-, 50-percent duration flows for the individual months of July, August, and September for all seven regions
- Seasonal low-duration streamflow statistics
- 98-, 95-, 90-, 85-, 80-, 70-, 60-, 50-percent duration flows for the season July-through-September for southeastern Alaska (Region 1)
- Seasonal 7-day low-flow frequency statistics
- 7-day, 10-year and 7-day, 2-year recurrence interval flows for southeastern Alaska (Region 1).
Peak-flow statistics presented in USGS Water-Resources Investigative Report 03-4188 are:
- Annual peak streamflow statistics
- 2-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year recurrence interval flows for all seven regions.
Both analyses were computed using data through the 1999 water year. Stations included in the analysis have at least 8 to 10 years of data. Data for USGS streamflow data-collection stations in Alaska are available at NWISWeb (http://waterdata.usgs.gov/ak/nwis/sw).