Pacific Southwest Research Station

Predicting Nutrient and Sediment Loading From Prescribed Fire Using WEPP

This project will optimize the Water Erosion Prediction Project (WEPP) model and predict sediment and nutrient loadings from slash pile burning at the hillslope scale using rainfall simulators and in situ sample collectors for naturally occurring events. This project will collaborate another Tahoe Science project, "Developing fuels treatments for balancing fuel reduction, soil exposure, and potential for erosion in the Tahoe Basin" by providing supplemental sampling of runoff for nutrients (phosphorus and nitrogen) at that project's prescribed fire sites. This collaboration will allow the project to adjust sampling in the event of a wildfire within the basin.

Full Title: Nutrient and sediment loading predictions for prescribed fire using optimized WEPP model

Proposal [pdf]

Lead Researchers: Drea Traeumer, Em Consulting; Mark Grismer, Integrated Environmental Restoration Services; Wally Miller, University Nevada-Reno

Goals

1. Locally optimize the WEPP model for predicting nutrient and sediment loading from prescribed fire during both the dry season and the snowmelt season, on both granitic and volcanic soils

Sampling Sites and Methods

• Use rainfall and runoff simulators at four prescribed fire sites (one volcanic and one granitic in each of 2 years) to measure hydraulic conductivity, interrill erodibility, bulk density, infiltration and runoff rates, sediment yield, sediment composition (particle-size distributions and organic matter content) and total and inorganic phosphorus and nitrogen concentrations in runoff
• Evaluate three treatments per site (undisturbed, slash piles, and woody-material piles). Burn pile characteristics will be measured, along with pre-burn soil moisture and fuel moisture, burn temperature and duration, and soil temperature.
• Conduct two rainfall and two runoff simulations for each treatment at both sites during both the dry season and the snowmelt season
• Conduct laboratory analyses to estimate sediment loads, including Total Suspended Solids and particle size distribution; dissolved nitrogen loads in runoff; dissolved phosphorus loads in runoff; and adsorbed phosphorus load
• Measure erosion at the hillslope-scale using silt fences for comparison to hillslope-scale predictions by WEPP
• Use precipitation data loggers at each site to measure rainfall intensity and amount for use in WEPP
• In the event of wildfire in the Tahoe basin during the term of this project, shift sampling efforts from two of the prescribed fire sites to two wildfire sites

Timeframe: August 2008 through September 2010 (2 years)
Products

1. Quarterly reports
2. Phase 1 summary report
3. Final technical report