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Research Project: Soil Erosion, Sediment Yield, and Decision Support Systems for Improved Land Management on Semiarid Rangeland Watersheds

Location: Southwest Watershed Research Center

2012 Annual Report

Objective 1. Provide databases, knowledge, and information on rangeland erosion at a range of spatial scales for the development, validation, and implementation of erosion decision tools. Objective 2. Develop decision tools including a rangeland specific hydrology and erosion model for improved planning and evaluation of rangeland management practices.

This project addresses the need for rangeland decision tools to assess the climatic and conservation management effects on rangeland sustainability as affected by runoff and erosion. The Natural Resources Conservation Service (NRCS) has requested that the Rangeland Hydrology and Erosion Model (RHEM) be integrated with a watershed scale model for the Conservation Effects Assessment Project (CEAP). Techniques to assess natural drivers and management practice effects on rangeland hydrologic and erosion processes at the hillslope or ecological site scale are primarily qualitative. Techniques are needed to quantify erosion rates and processes, particularly under disturbed conditions where data are lacking. At larger scales, the impact of conservation structures on sediment dynamics is poorly understood. Tools are needed that integrate the effect of management practices implemented at the hillslope scale with watershed scale processes to assess their environmental impact and cost effectiveness. The general approach of this project is to develop databases, knowledge, and information that will be used to evaluate conservation practices and quantify the physical and effectiveness of those practices on reducing runoff and erosion at the hillslope and watershed scale. The expected outcomes of the research are 1. Databases and improved measurement techniques to quantify a) decadal-scale hillslope erosion rates, b). overland flow erosion for disturbed conditions, c) sediment transfers as impacted by conservation structures and d). landscape change; 2. Integration of RHEM and KINEROS2 in the GIS based AGWA framework for rangeland conservation practice assessment; and 3. A framework to assess effectiveness of conservation practices.

Progress Report
This report documents progress for Project Number 5342-12660-005-00D, which started in February 2012 and continues research from Project Number 5342-12660-004-00D, entitled “Soil erosion, sediment yield, conservation structures, and dss for sustainable land management on semiarid rangeland watershed.” Progress was made on both objectives and their sub-objectives, all of which fall under National Program 211 Problem areas 2 erosion, sedimentation and water quality protection, 3 improving conservation effectiveness, and 4 improving watershed management and ecosystem services in agricultural landscapes. Under Objective 1, progress was made in quantifying decadal-scale soil erosion rates in semi-arid landscapes as a function of ecological site descriptions. Twelve ecological sites and their states were identified and characterized for vegetation parameters on the Empire Ranch in southeastern Arizona, and soil samples were collected for 137C analyses. Rainfall simulations were completed on the reference site and two alternate states of the Clay Loam Upland Ecological Site in MLRA 38. Progress was made in scanning and uploading historic contact prints taken by SCS personnel in the 1930s on the San Simon Watershed. Significant progress was made in assembling, verifying, and updating the San Simon watershed stock tank database and creating GIS layers. QA/QC procedures were developed and implemented for processing the new digital data stream from Walnut Gulch Experimental Watershed stock tank runoff and sediment yield datasets. Hardware consisting of a weatherproof housing, solar powered battery system, and an electronic timer based remote trigger system was assembled to build a ruggedized very high resolution camera system. The system was deployed and field tested. Under Objective 2 significant progress was made in collaboration with ARS scientists in Boise, Idaho, on developing a dynamic Rangeland Hydrology and Erosion Model (RHEM) and parameters for describing disturbed rangeland sites. The dynamic RHEM code has been developed and incorporated into the KINEROS model for inclusion into the watershed analysis tool AGWA. A database was created that links grazing, brush management, fences, and prescribed fire management practices with precipitation and field and remotely sensed vegetation monitoring data for the Empire Ranch.


Review Publications
Guber, A.K., Pachepsky, Y.A., Yakirevich, A., Shelton, D.R., Sadeghi, A.M., Goodrich, D.C., Unkrich, C.L. 2011. Uncertainty in modeling of fecal coliform overland transport associated with manure application in Maryland. Hydrological Processes. 25:2393-2404.
Goodrich, D.C., Guertin, D.P., Burns, I.S., Nearing, M.A., Stone, J.J., Wei, H., Heilman, P., Hernandez, M., Spaeth, K., Pierson Jr, F.B., Paige, G.B., Miler, S.N., Kepner, W., Mcclaran, M.P., Weltz, M.A., Jolley, L. 2011. AGWA: The Automated Geospatial Watershed Assessment Tool to inform rangeland management. Rangelands. 33(4):41-47.
Rhoton, F.E., Emmerich, W.E., McChesney, D.S., Nearing, M.A., Ritchie, J.C. 2011. Sediment source identification in a semiarid watershed at soil mapping unit scales. Catena. 87:172-181.
Renard, K.G., Yoder, D.C., Lightle, D.T., Dabney, S.M. 2011. Universal soil loss equation and revised universal soil loss equation. In: Handbook of Erosion Modeling. R. Morgan and M. Nearing, editors. Part 2; Chapter 8:137-167.