Submitted to: Laboratory Publication
Publication Type: Government Publication
Publication Acceptance Date: 6/28/2006
Publication Date: 6/28/2006
Citation: Simon, A. 2006. Estimates of fine-sediment loadings to Lake Tahoe from channel and watershed sources. USDA-ARS National Sedimentation Laboratory Research Report No. 52. 59 pp.
Interpretive Summary: The delivery of fine-grained sediment from tributary basins is listed as a major cause of water-clarity deterioration in Lake Tahoe. Efforts to control the discharge of fine sediment to the lake require knowledge of the volumes, rates and sources of this material. Similarly, use of a lake-clarity model to predict future clarity conditions and the effectiveness of management alternatives also require these types of data. The research described in this report used combinations of field-based observations of channel and bank stability with measured and simulated data on fine-sediment loadings to estimate fine-sediment loadings from un-monitored basins throughout the Lake Tahoe Basin. Loadings were expressed in the conventional format of mass per unit time (tonnes per year) but also in the number of particles finer than 20 'm, the latter for use in a lake-clarity model operated by the University of California, Davis.
Technical Abstract: The research described in this report used combinations of field-based observations of channel and bank stability with measured and simulated data on fine-sediment loadings to estimate fine-sediment loadings from un-monitored basins throughout the Lake Tahoe Basin. Fine-sediment (<0.063) loadings in tonnes per year for each un-monitored watershed were based on extrapolating relations between distributions of a combined-stability index and measured fine yields (T/y/km2) within each basin quadrant. The greatest contributors happened to be those with measured data, not requiring extrapolation. In descending order they are: Upper Truckee River (1010 T/y), Blackwood Creek (846 T/y), Trout Creek (462 T/y) and Ward Creek (412 T/y). Summing the values from the contributing watersheds provided an average, annual estimate of fine-sediment (<0.063 mm) loadings to the lake of 5,206 T/y. Average, annual fine-sediment loading from streambank erosion of 1,305 T/y. This represents about 25% of the average, annual fine-sediment load delivered to the lake from all sources. The two largest contributors, the Upper Truckee River (639 T/y) and Blackwood Creek (431 T/y), account for slightly more than 80% of all fines emanating from streambanks, representing about 20% of fine sediment delivered to Lake Tahoe from all sources.