Research Projects

Lake Tahoe Water Quality and Shore Erosion Study

PI: Kenneth D. Adams

Project Period: October 2000 - March 2002

Funded by: Tahoe Regional Planning Agency and U.S. Bureau of Reclamation through URS Greiner Woodward Clyde

Right: Lake Tahoe shore

Keywords: Lake Tahoe, shoreline erosion, water quality

Problem Definition

The shore zone surrounding Lake Tahoe is a very dynamic environment where sediment is eroded, transported, and deposited on an annual basis. Waves in the nearshore area also help to redistribute sediment delivered to the Lake by inflowing streams. However, until recently the extent of shoreline erosion, littoral sediment movement, and its effect on the water quality of Lake Tahoe was relatively unknown. Beginning in February of 2000, the Desert Research Institute has been conducting a study to determine the amount of shoreline change over the last 60 years in the Tahoe basin by using a combination of historical aerial photographs in a GIS database and field work documenting shoreline change. One of the primary purposes of this study is to determine the amount of nutrient loading (nitrogen and phosphorus) into the lake from shoreline erosion. To date, aerial photographs from 1938, 1939, and 1940 have been collected, rectified, mapped, and compared to 1992 and 1998 imagery for almost the entire lakeshore, thus documenting the overall amount of shoreline change over a 60-year period. Photographs from 1952, 1963, and 1995 have also been incorporated into the GIS database. Preliminary results suggest that some areas have undergone as much as 10 to 15m of erosion since 1938, while large reaches of the shore are relatively little changed during the same period. There appears to be a correlation between the type of shore and backshore material and the amount of change, but this has not yet been effectively demonstrated. This phase of the project has provided a broad view of changes in the shorezone and impacts to the lake but more detailed work needs to be accomplished.

Project Approach

The goals of the current phase of the study are to increase our understanding of the shorezone system of Lake Tahoe, the physical processes operating within this system, and the effect of these processes on water clarity within the Lake. To attain these goals we will integrate field studies documenting the wind and wave characteristics of the Lake and the geological properties of eroding areas. Field studies will be in addition to continuing efforts designed to quantify and refine the rates of shoreline change using aerial photography incorporated into a GIS database.

Return to Projects List