Location: Watershed Physical Processes Research2013 Annual Report
1a. Objectives (from AD-416):
Improve science components for the RUSLE2 conservation planning tool and facilitate incorporation of these improvements into the functional RUSLE2 model implemented by NRCS. Specifically, support implement by National Resource Conservation Service (NRCS) of improved modeling of pasture, hay, and other perennial vegetations; track management effects on soil organic matter and link to sediment characteristics; develop and incorporate an ephemeral gully component; support ARS efforts to expand RUSLE2 to 2-D landscape modeling; and support NRCS implementation of this science, document science improvements.
1b. Approach (from AD-416):
Incorporate into RUSLE2 the following: track changes in soil organic; effects of organic matter on eroded sediment size distribution based on literature analysis, lab, and field research; an ephemeral gully component based on an improved CREAMS approach; support implementation of new perennial vegetation science; and expand RUSLE2 to a 2-D landscape approach incorporating impacts of runoff redirection and deposition. Develop materials for National Resource Conservation Service (NRCS) explaining those changes and provide implementation assistance.
3. Progress Report:
The Revised Universal Soil Loss Equation Version 2 (RUSLE2) has been significantly improved in how it handles pasture, hay, and other perennial vegetation. These improvements have been primarily in trouble-shooting how the program works within the RUSLE2 management and profile, as well as adding some new features, including how the program transitions between various types of vegetation. In addition, as a response to questions raised by Natural Resources Conservation Service's (NRCS) national implementation, additional minor improvements have been made. The ARS efforts to expand RUSLE2 technology to a 2-D landscape model include several key elements that must be addressed. Previous reports included discussion of the complete re-writing of the code to perform the calculations on a cell rather than slope segment basis. The older profile-based approach was then adapted so that it could generate cells and define the relationships between those, which on testing proved (as hoped) to give the same answers as did the older calculations. As the cell-based calculations become more efficient, the hope is to completely do away with the segment-based calculations. During this reporting period, significant progress was made in optimizing the code to increase speed and calculation efficiency, including especially refactoring of the code to require less use of the RUSLE engine. Various other natural resource programs are using the RUSLE2 Dynamic Link Library (DLL), which allows those programs to set RUSLE parameters and get RUSLE2 results without using the RUSLE2 interface. Examples of these programs include the Soil Nutrient Application Planner (SNAP) from Wisconsin, the Manure Management Planning (MMP) tool at Purdue, and most notably the Natural Resource Inventory (NRI) effort for NRCS, based at the University of Iowa. The latter especially will make a huge number of calls to the RUSLE2 program, and is setting inputs in new ways. During this reporting period some effort has gone into trouble-shooting use of the dll for these uses. Finally, the code was adapted to make use of the Rothemsted carbon model (ROTH-C) approach to modeling carbon sequestration in the soil. This included linkage of the RUSLE decomposition routines to that approach. This method appears to work well, but will require some calibration of the approach to adequately represent various land uses and soil moisture effects.