Conservation Effects Assessment Project-Grazinglands
Northwest Watershed Management Research
2013 Annual Report
1a.Objectives (from AD-416):
To provide quantitative information and analytical tools that can be used to evaluate the impact of selected grazingland conservation practices on natural resource values.
1b.Approach (from AD-416):
Enhance and test the Rangeland Hydrology and Erosion Model (RHEM) for use on disturbed rangeland sites including fire, juniper encroachment and cheatgrass invasion.
This report serves to document research progress over the 1-year span of this project. The erosion components of the dynamic version of the Rangeland Hydrology and Erosion Model (RHEM) were tested against rainfall simulation data for three different sites disturbed by fire and/or by tree encroachment. Model performance was conducted with and without calibrating the erodibility parameters in order to also evaluate the parameter estimation equations. Results indicated that the model accurately predict erosion at the plot scale with a satisfactory range of error even using the parameter estimation equations. The new version of the model was able to match the predicted effect of disturbances and treatments across a wide range of ecological sites and vegetation and ground cover conditions. These enhancements to RHEM create a practical management tool for quantifying erosion and assessing erosion risk following rangeland disturbance, as well as, for conservation planning and quantifying environmental benefits of alternative conservation practices. The tool can use readily available vegetation and ground cover data to determine the degree of disturbance impact on erosion and track the rate of site recovery. In addition, ARS scientists in Boise, Idaho, continued to work closely with ARS scientists in Tucson, Arizona, on efforts to improve estimates of runoff contributions from snowmelt in the Automated Geospatial Watershed Assessment (AGWA) tool by taking detailed outputs from a physically-based snow accumulation and melt model (ISNOBAL) and providing them as input to AGWA. Testing the level of detailed snow information needed to improve large-scale runoff estimates from snow-dominated landscapes using AGWA is now underway. This agreement was established in support of objective 1 (Sub-Objective 1.B) of the in-house project, the goal being to develop management tools for hydrologic and erosion assessment of the impacts of fire, weed-invasions, and conservation practices on Great Basin sagebrush steppe rangelands to aid public and private land managers in formulating conservation strategies and selecting effective conservation practices by enhancing the Rangeland Hydrology and Erosion Model (RHEM) for assessing hydrology and erosion responses associated with management of disturbed states and transitions occurring on sagebrush steppe ecological sites.