The study area, which included Alaska and conterminous basins in Canada, was divided into seven 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 and peak flows but with Region 4 for low-duration flows. Seasonal low-flow frequency statistics for Regions 1 and 3 indicated that these regions are too dissimilar to be combined for this particular analysis; equations were developed for Region 1, but not Region 3, because there were too few stations in Region 3. Region 7 contains very few stations but could not logically be combined with adjoining regions.
Alaska Geospatial Data Clearinghouse: Streamflow analysis regions for Alaska and conterminous basins in Canada
Estimating high and low-flow statistics (WRIR 03-4114): Plate 1 (PDF, 3.66 MB)
Estimating peak streamflows (WRIR 03-4188) : Plate 1 (PDF, 3.84 MB)