The hydrographs open in a small window, and use the federal water year, which runs from the beginning of October through the end of September, and is named for the year in which it ends. Somers data were used for 1928-1998. Polson data were used for 1911-1926 and 1998-2005. Hydrographs for 1908-1910, parts of 1916 & 1917, 1919, parts of 1923-1926 & 1928, and all of 1927, were generated from lake levels that were estimated from streamflow data from the gauge on the Flathead River below Polson. Calculated levels are displayed in red. Measured levels are displayed in blue. An informal comparison of the gauges indicates a difference of approximately one-tenth-foot, with the higher number at Somers. The difference is of no practical consequence for the purposes of this page.