ILLUSTRATIONS DEFINITION OF TERMS Water year: A water year is a 12-month period, October 1 through September 30, designated by the calendar year in which it ends. In this report, years are water years unless otherwise noted. Sea level: In this report "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929) a geodetic datum derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called Sea Level Datum of 1929.

This report contains data collected during a 4-year study of sediment sources in four drainage basins tributary to Lake Tahoe, California-Nevada: Blackwood, General, Edgewood, and Logan House Creek basins. Data include changes in bank and bed positions at channel cross sections, results of streamchannel mapping, analyses of bank and bed material samples, tabulations of bed material point counts, measured rates of hi 11 slope erosion, dimensions of gullies, suspended-sediment data collected during synoptic snowmelt sampling, and physiographic data for the four study basins.