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United States Department of Agriculture

Agricultural Research Service

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Research Project: Evaluating the Effects of Conservation Practices on Western Rangelands

Location: Southwest Watershed Research

2013 Annual Report

1a. Objectives (from AD-416):
The objectives of this cooperative research project are to develop new methods and technologies to assess the effectiveness of conservation practices currently employed on rangelands of the Western United States. The project involves the measurement and modeling of hydrology, erosion and sediment yield at a range of scales, with an emphasis on the development of a dynamic model with capability to interface with the watershed models and a user-friendly, web-based interface for representing both disturbed and undisturbed site conditions on rangelands with risk-based analysis, with capability for representing orographic precipitation effects, and with inter-storm updates to key model parameters. The tool will be implemented and tested for application to the USDA Conservation Effects Assessment Project (CEAP). Challenges include the ability to model hydrologic and sediment-related processes across scales ranging from a few meters to kilometers. The approach will entail significant geospatial database and modeling needs which are acquired through our cooperator at the Univ. of Arizona.

1b. Approach (from AD-416):
The project will a) change RHEM model equations from the current steady-state to fully dynamic (DRHEM) so that intra-storm changes in erodibility common to many disturbed conditions can be represented, b) incorporate existing technology based on PRISM and CLIGEN into the DRHEM model framework to allow modification of precipitation and temperature inputs to account for orographic effects that dominate spatial patterns on the western U.S., c) provide new data for DRHEM model development, parameter estimation, and validation studies, d) develop a catalog of DRHEM input for Ecological Site Descriptions and critical rangeland management practices, e) develop a catalog of the spatial and temporal scale of rangeland BMPs and how they should be represented in the watershed model at the larger allotment or landscape scale, f) couple DRHEM and KINEROS2 and test over a range of conditions, g) integrate the DRHEM/KINEROS2/SWAT model into the AGWA GIS framework, h) develop AGWA tools to delineate and represent rangeland conservation management practices with NRCS, and i) conduct large area testing of the integrated tool in close coordination with the ARS pilot watershed effort for Rangeland CEAP.

3. Progress Report:
This project contributes to objective 2 of the in-house project, "Develop decision tools including a rangeland specific hydrology and erosion model for improved planning and evaluation of rangeland management practices". Initial analysis of data from fire-disturbed rangeland sites illustrated the importance of intra-storm dynamics on soil erodibility and the dominance of detachment by small concentrated flow channels as opposed to broad sheet flow. Therefore the steady-state solution of the Rangeland Hydrology and Erosion Model (RHEM) equations were solved within the dynamic framework of KINEROS2, with additional capability to dynamically update soil erodibility parameters for both concentrated and sheet flow within storm events. The dynamic RHEM code was also integrated into a stand-alone web site application that allows users anywhere to run and use the model. Results of research in collaboration with ARS in Boise, Idaho, were used to develop parameter estimation equations for concentrated flow on disturbed rangeland sites. Significant efforts were also directed to conducting a Conservation Effects Assessment Project (CEAP) Rangeland pilot project on the Cienega Creek Watershed in Southeastern Arizona. For this watershed pre-conservation periods were defined based on conservation spending levels and RHEM parameters were determined for this period and from 2003-2006 NRI data. Model simulations using RHEM, and KINEROS2/RHEM in the Automated Geospatial Watershed Assessment (AGWA) tool over the watershed were conducted. Successful research was also conducted demonstrating the ability to utilize nationally available remotely sensing imagery to detect shrub and non-shrub canopy cover and the impacts of shrub removal by fire and mechanical methods.

4. Accomplishments

Last Modified: 10/17/2017
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