ARS | Publication request: Lake Tahoe Basin Framework Implementation Study: Sediment Loadings and Channel Erosion

Submitted to: Laboratory Publication
Publication Type: Government Publication
Publication Acceptance Date: February 10, 2004
Publication Date: February 10, 2004
Citation: Simon, A., Langendoen, E.J., Bingner, R.L., Wells, R., Heins, A., Jokay, N., Jaramillo, I. 2004. Lake tahoe basin framework implementation study: sediment loadings and channel erosion. USDA-ARS National Sedimentation Laboratory Research Report. No. 39. 377 pp.

Interpretive Summary: Because of concerns regarding a decline in the clarity of Lake Tahoe, a study was designed to combine detailed analysis of several representative watersheds with reconnaissance level evaluation of approximately 300 sites to determine which basins and areas were contributing sediment to Lake Tahoe. Numerical modeling of upland- and channel-erosion processes over then next 50 years was conducted using AnnAGNPS and CONCEPTS, respectively on General and Ward Creeks, and the Upper Truckee River. GIS-based analysis of land use, land cover, soil erodability, steepness, and geology was used to evaluate upland-erosion across the basin. Channel contributions were determined by comparing cross-sectional shapes of five channels originally surveyed in either 1983 or 1992. Historical flow and sediment-transport data from more than 30 sites were used to determine bulk suspended-sediment loads (in tonnes) and yields (in tonnes/km2) for sites all around the lake. Eighteen index stations were selected and used to make comparisons between sediment production and delivery from individual watersheds and between different sides (directional quadrants) of the lake. Fine-grained sediment transport was determined from historical data for 20 sites based on relations derived from particle-size distributions across the range of measured flows.

Technical Abstract: Because of concerns regarding a decline in the clarity of Lake Tahoe, a study was designed to combine detailed analysis of several representative watersheds with reconnaissance level evaluation of approximately 300 sites to determine which basins and areas were contributing sediment to Lake Tahoe. Suspended-sediment loads and yields vary over orders of magnitude from year to year, from west to east and north to south across the basin. Median annual suspended-sediment loads for index stations range from about 2200 tonnes/yr (T/y) from the Upper Truckee River to 3 T/y from Logan House Creek. Based on historical data, the largest annual contributors of sediment are in decreasing order, Upper Truckee River (2200 T/y), Blackwood Creek (1930 T/y), Second Creek (1410 T/y), Trout Creek (1190 T/y), Third Creek (880 T/y) and Ward Creek (855 T/y). Data from Second and Third Creeks may be somewhat misleading though because of a short period of data collection in the case of the former, and the fact that data collection occurred during major construction activities in these basins. Analysis of suspended-sediment transport ratings with longer periods of record (17 to 20 years) show that sediment loads from the northeast streams have significantly decreased across the entire range of flows. Based on historical data, the lowest contributors of suspended sediment from index stations, in increasing order are Logan House (3.0 T/y), Dollar (4.6 T/y), Quail Lake (6.4 T/y), Glenbrook (8.9 T/y), and Edgewood Creeks (21.3 T/y). Fine-grained loads show a similar pattern as total loads with the greatest contributors being the Upper Truckee River (1010 T/y), Blackwood Creek (844 T/y), Trout Creek (462 T/y) and Ward Creek (412 T/y).