2013 Annual Report
1a.Objectives (from AD-416):
Develop an Online Watershed Interface to predict the effects of forest and
fire management on sediment and nutrient loads in surface runoff in the Lake Tahoe Basin.
1b.Approach (from AD-416):
In order to reduce fire risk within forested areas in the Tahoe Basin, numerous fuel management activities to thin, harvest, burn and masticate excessive fuels are necessary. To support these activities a road network with landings is required. We propose to meet with stakeholders in the basin to determine the current fuel management activities. We will then develop watershed tools to allow managers to evaluate the subwatershed effects of these activities in terms of fine sediment and phosphorus delivery from subwatersheds that were treated. The approach to the tool will be based on previous work supported by the SNPLMA and others. In Round 7, three products based on the Water Erosion Prediction Project (WEPP) Model were generated to aid in evaluating sources of sediment in the Lake Tahoe Basin, and the effects of forest management on sediment generation. One was a database including the digital elevation model for the basin, the soil maps, the land coverage, and a weather database including all SNOTEL stations within the basin. The second product was an online interface to run individual hillslopes to estimate the runoff and sediment generation associated with wildfire and forest management. The third product was a series of calculations to use the WEPP model to predict the distribution of erosion within the basin under the current cover. In a complementary project, an online GIS interface is under development for the WEPP watershed version to allow users to run WEPP Watershed without the need to be proficient in, or even purchase a GIS. Another WEPP development is the incorporation of water quality algorithms by Forest Service researchers into WEPP runoff and sediment predictions. We propose to incorporate the Tahoe Basin database into the online WEPP Watershed interface to allow users to carry out watershed analyses within the Tahoe Basin. We will then enhance that online interface to include the Round 7 enhancements to allow a more comprehensive analysis of runoff and water yield from the basin. The interface will be further enhanced to include a channel flood routing and erosion prediction currently not available with the WEPP technology. The proposed output interface will be developed to aid in interpreting model predictions, and in linking those predictions to the Tahoe Basin TMDL. To estimate the erodibility of landings, soil erodibility properties will be measured by two types of rainfall simulators and a constant head permeameter. The results will be added to a growing database of Tahoe-specific WEPP soil erodibility values. During the project, semi annual teleconferences will be held between the stakeholders and the research team. At the end of the project, a workshop will be held to train potential users on using the tool. A monitoring program will be initiated using flumes and turbidity meters, along with grab samples to see if sediment from forest management activities can be detected at the subwatershed scale on two disturbed and two undisturbed forested subwatersheds.
An initial meeting with shareholders in the Lake Tahoe Basin was held on March 26, 2013 at the Lake Tahoe Regional Planning Agency office in Stateline, Nevada. Web-based WEPP GIS software at the ARS-NSERL has been shared with Forest Service cooperators, and a new server is being set up at the University of Idaho, in Moscow, Idaho. Work has begun on obtaining downscaled global environmental model climate scenarios for use in WEPP model simulations in the Lake Tahoe area.