Flow Duration and Low-Flow Frequency Studies in Alaska Active

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Basin characteristics

Basin characteristics are physical and climatic features used as independent variables for estimating streamflow. Basin characteristics for an ungaged site that are substituted in the estimating equations should be determined by the same methods as those used to develop the equations. USGS WRIR 2003-4114 table 1 lists the sources for the various basin characteristics for estimating flow-duration and low-flow frequency statistics. For WRIR 2003-4114 equations containing climate variables, values should be obtained from the following datasets (rather than any newer datasets):

• For determining mean minimum January temperature, use Plate 1 (PDF, 5.75 MB) from "Magnitude and frequency of floods in Alaska and conterminous basins of Canada" by S.H. Jones and C.B. Fahl (1994).

• For determining mean annual precipitation, use Plate 2 (PDF, 6.48 MB) from "Magnitude and frequency of floods in Alaska and conterminous basins of Canada" by S.H. Jones and C.B. Fahl (1994).

Regions

For USGS WRIR 03-4114, the study area was divided into seven streamflow analysis regions based on hydrologic boundaries, geographic distribution of basin characteristics, and results of regressions with peak, high-duration, and low-duration streamflow data. For consistency between analyses, regional boundaries are constant. However, regions were combined as hydrologically appropriate to develop equations, such that Region 3 is grouped with Region 1 for high-duration flows but with Region 4 for low-duration flows.

• The streamflow analysis region boundaries for use with USGS WRIR 03-4114 are available in GIS form by emailing ascweb@usgs.gov and asking for Streamflow analysis regions for Alaska and conterminous basins in Canada. 

• A map showing the streamflow analysis regions can be downloaded from USGS WRIR 03-4114 as Plate 1 (PDF, 3.66 MB).

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Statistics/equations

Flow-duration and low-flow frequency statistics for gaged sites and regression equations for estimating the statistics at ungaged sites are available from USGS WRIR 03-4114 in PDF and in spreadsheet form.

Statistics

• Annual high-duration flow statistics (table 7, 73 KB) EXCEL

• Monthly low-duration flow statistics (table 8, 99 KB) EXCEL

• Seasonal low-duration flow and low-flow frequency statistics (table 9, 33 KB) EXCEL

Regression equations

• Annual high-duration flow regressions (table 2, 29 KB) EXCEL

• Monthly low-duration flow regressions (table 4, 50 KB) EXCEL

• Seasonal low-duration flow and low-flow frequency regressions (table 5, 24 KB) EXCEL