USDA Forest Service

Pacific Southwest Research Station

Pacific Southwest
Research Station

800 Buchanan Street
Albany, CA 94710-0011
(510) 883-8830
United States Department of Agriculture Forest Service. USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.

Assessing the sources and transport of fine sediment in response to management practices in the Tahoe Basin using the WEPP model

Principal Investigators:
Erin Brooks, University of Idaho
William Elliot, USDA Forest Service-Rocky Mountain Research Station
Jan Boll, University of Idaho
Joan Wu, Washington State University

Proposal [pdf]

Final Report [pdf]

Additional Report: Brooks and Boll, 2011 [pdf]

Please contact Dr. Erin Brooks with questions regarding the final report.

Project Summary

The goal of this project was to test and develop the Water Erosion Prediction Project (WEPP) model as a watershed management tool for evaluating the impacts of specific management practices on the generation of fine (<20 micron) sediment transport at the hillslope and watershed scales in the Lake Tahoe Basin. The project provided a Tahoe-specific database which includes all the necessary soil, climate, and management input files to run the model at any location in the basin.

The accuracy of the model was tested against 18 years of observed snow water equivalent depth, streamflow and sediment load data at the following relatively undisturbed watersheds: Blackwood Creek, General Creek, Upper Truckee near Meyers, Logan House Creek, and Glenbrook Creek. Close agreement between simulated and observed snow water equivalent, streamflow, and both fine (<20 micron) and coarse (>20 micron) sediment load was achieved at each of the major watersheds located in the high precipitation regions of the basin with minimal calibration. Minimal sediment load was correctly simulated in the drier watersheds (i.e., Logan House and Glenbrook); however, annual streamflow was overpredicted. This overprediction was attributed to unique hydrogeology on the east side of the basin.

The project also provided Tahoe-specific soil and management input files for representing the impact of hillslope disturbances and subsequent restoration options on fine sediment loading. These input files were created using existing rainfall simulation data collected in the basin over the past 10 years. Major land cover treatments include: mature forest, thin or young forest, shrubs, good grass, poor grass, low-severity fire, high-severity fire, bare, mulch only, mulch and till, low-traffic road, high-traffic road, and skid trail.

A high priority was placed on developing user-friendly tools and providing training. A simple web-interface tool was developed and populated with the Tahoe-specific input files to allow end users to easily predict the impact of disturbances on fine sediment loading from single hillslopes. The input files were also modified to allow access to the Tahoe-specific input files in the WEPP-windows program. This free program, operating in the windows environment, provides experienced users greater flexibility for simulating impacts of management practices from complex hillslopes. For advanced users, algorithms were provided to simulate streamflow and fine sediment loading from large complex watersheds.