Applicability of an Online Decision-Support Tool (WEPPcloud) to Watershed-Scale Forest Management in the Western US

Abstract. The Water Erosion Prediction Project (WEPP) model is a process-based computer simulation model that has been widely used in research and by land managers to predict runoff and soil erosion from both agricultural and forested areas. While the model can produce accurate predictions with proper input data and minimal calibration, its usability has been limited by data accessibility and processing, and model setup. WEPPcloud is a free online interface developed mainly for forest applications that allows users to run WEPP without explicit knowledge of GIS and computer programming or even the area being modeled. All input files for the WEPP model are either automatically created from freely available databases or are used directly from an extensive WEPP database stored locally on the server. WEPPcloud also includes algorithms to simulate phosphorus yield based on simple static phosphorus concentrations in surface runoff, subsurface lateral flow, baseflow, and particulate phosphorus concentration attached to sediment. Recently, the WEPPcloud capabilities have been used in various applications to aid land managers with making decisions about pre- and post-fire fuel management and soil erosion. We will specifically present results from a basin-wide modeling effort in the Lake Tahoe Basin (Figure 1) where we compared several management scenarios (uniform high, moderate, and low severity, uniform thinning, simulated wildfire under current climate and future climate conditions) to current management conditions based on historic weather data. Similarly, we will demonstrate the applicability of the WEPPcloud interface to two municipal watersheds in Portland and Seattle, respectively. All hydrologic simulations were conducted online with the WEPPcloud interface. Minimum calibration was performed on watersheds using data from a USGS gauging station and calibrated parameters were applied uniformly to all modeled watersheds. All results are for individual hillslopes, channels, and at each watershed outlet. Average annual surface runoff, lateral flow, baseflow, sediment detachment, deposition, and yield, and total phosphorus, soluble reactive phosphorus, and particulate phosphorus are displayed both in tabular (as a text file) and visual (as a shapefile) format for each individual watershed or for multiple watersheds combined. Managers can further use these results to sort and select hillslopes that are generating more runoff and erosion based on specific hillslope attributes such as slope steepness or soil or management type for each simulation scenario. Lastly, we will discuss advantages and disadvantages of using online interfaces for hydrologic modeling and forest management.