Science Application and Integration 240 W. Prospect RdRdRd . | Fort Collins, CO 80526 | (970) 498 ---1100 | www.fs.fed.us/rmrs Program Wildf ire Effects on and Stream Water erosion, stream water quality, and National Fire Plan stream water yield are of great concern Research Highlight following a . Scientists at the USDA Forest Service, Rocky Mountain October 2011 October 2011 Research Station (RMRS), in Moscow, ID, have been modeling post-fire processes for years with the Terry Hardy

Providing Watershed Project Graduate studen t Mariana Dobre records ground cover scientific (WEPP) model . Now, they are improving following a simulated wildfire. knowledge and the model by expanding its hydrologic technology to prediction abilities. Their work Recent data collection and modeling sustain our work at the Boise Basin Experimental nation’s forests, contribute s knowledge and methods , and for predicting the abundance, quality, Forest show that t he amount of mineral grasslands and reliability of water from our soil exposed after a fire is generally nation’s forests under changin g land greater on south -facing slopes, where use and var iable climate conditions. ground surfaces receive more solar radiation , and on shoulders of hills, How Does Fire Impact Water Quality? rather than near the bottoms of slopes. Fires not only consume vegetation; they also affect soil structure, porosity, "This data will help respond to our and hydraulic conductivity . In a post- forest p lan monitoring elements as fire environment , soil erosion can lead well as project level analy sis." to excessive sedimentation in forest streams, potentially degrading water —Terry Hardy, Boise National Forest quality and reducing water yield in For additional streams that are critical for The WEPP Model information, maintaining water supplies and The WEPP model can be applied to contact: aquatic habitats. range land , agricultural, and forested watersheds . Based on user input G. Sam Foster Exposed mineral soil is usually the describing climate, soil properties, and RMRS Director most i mportant fire -related factor that vegetation , the model estimates soil can be measured to estimate potential 970-498-1353 loss, water yield, and delivery soil erosion after a fire. [email protected] to streams . Two significant impacts of fire on soil Scientists at the RMRS developed input and water quality are: data for WEPP that describe the growth, On many , gases from burning yield, and decomposition of forest vegetative cover can coalesce in plants. New geospatial interfaces for the soil and cause a water WEPP can be used to delineate repellent layer that increases watershed s. T hus, forest managers can runoff. use WEPP to make decisions about When vegetative cover is burned, post-fire mitigation activities at a exposed mineral soil is more likely watershed scale . Compiled by USDA to detach from slopes, leading to Forest Service, EMC increases in runoff and erosion Publishing Arts. during rain and snowmelt events. Improving WEPP as a Hydrologic M odel Forest streams receive runoff from three main sources: surface flow, subsurface shallow lateral flow, and base flow. Peak stream flows are mainly influenced by from large precipitation or snowmelt events. When stream flow starts to decline after snowmelt in upland forest watersheds , it is dominated by subsurface lateral flow . In the late summer, stream water often consists entirely of base flow . Studies suggest that watersheds have different dominant runoff proce sses, with surface runoff more important on the smaller A typical forest hydrograph, from a tributary of Lake Tahoe, watersheds, lateral flow on the mid-sized watersheds, and ground - shows the relative roles of surface runoff, subsurfsubsurfaceace shallow water on the larger watersheds. lateral flow, and base flow. Source: Dr. Erin Brooks. In 2006 , RMRS scientists incorporated lateral flow into the WEPP model with great success. Now, they are working to incorporate For more information, see these recent base flow. To test the new WEPP base -flow technology, they publications: modeled five large watersheds draining into Lake Tahoe for five Dobre, M. 2010. Assessin g spatial distribution years and compared WEPP-simulated stream flow with measured of fire effects in forests using GIS. In stream flow. WEPP performed reasonabl y well. Proceedings of the 2 nd Joint Federal Interagency Conference, 27 June – July 1, Las Vegas, NV. Available online at < “Clean, healthy forests are vital to our efforts to protect America’s http://acwi.gov/so s/pubs/2ndJFIC/index.ht fresh water supply… Our nation’s economic health, ml > Accessed Dec, 2011. 11 p. and the health of our citizens, depends on abundant, Elliot, W, Brooks, E, Link, T, Miller, S . (2010) clean and reliable sources of freshwater .” Incorporating groundwater flow into the WEPP model. In Proceedings of the 2 nd –Thomas Vilsack USDA Secretary Joint Federal Interagency Conference, 27 June – July 1, Las Vegas, NV. Av ailable Ongoing Research online at < http://acwi.gov/sos/pubs/ 2ndJFIC/index.html > Accessed Dec, 2011. Scientists continue to refine the baseflow component of WEPP for 12 p. more accurate predictions and for watersheds with varying Srivastava, A., M. Dobre, E. Bruner, W.J. Elliot, climatic and geological settings. As they make progress simulating I.S. Miller, and J.Q. Wu. 2011. Application processes like wildfire effects, evapotranspirtation , snow Of The Water Erosion Prediction Project accumulation, and snowmelt, they hope to improve prediction of (WEPP) Model to Simulate Stream flow in a peak flows and water yield. PNW Forest Watershed. Presented at the International Symposium on Erosion and Scientists also continue to study correlations among fire effects Landscape Evolution, 18 -21 September, and soil, topographic, and climatic v ariables . By learning to target 2011. Anchorage, AK. Paper no. 11040. St. practices that minimize erosion according to landscape Joseph, MI: ASABE. 8 p. topography, managers could save time and money in fuel treatment planning or post-wildfire mitigation activities. Lead Scientist: Bill Elliot, Rocky Mountain Research Station, Moscow, ID [email protected] , http://forest. moscowfsl.wsu.edu/fswepp/