Evaluation of Conservation Effects Assessment Project Grazing Lands conservation practices on the Cienega Creek Watershed in southeast Arizona with RHEM/KINERSO2/AGWA modeling tools

Authors: Goodrich, David - Dave; WEI, H. - University Of Arizona; BURNS, I.S. - University Of Arizona; GUERTIN, D.P. - University Of Arizona; SPAETH, K. - Natural Resources Conservation Service (NRCS, USDA); Hernandez, Mariano; Holifield Collins, Chandra; Kautz, Mark; Heilman, Philip - Phil; LEVICK, L.R. - University Of Arizona; Ponce Campos, Guillermo; CARRILLO, E. - Natural Resources Conservation Service (NRCS, USDA); TILLER, R. - Arizona Department Of Environmental Quality

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2019
Publication Date: 5/1/2020
Citation: Goodrich, D.C., Wei, H., Burns, I., Guertin, D., Spaeth, K., Hernandez Narvaez, M.N., Holifield Collins, C.D., Kautz, M.A., Heilman, P., Levick, L., Ponce Campos, G.E., Carrillo, E., Tiller, R. 2020. Evaluation of Conservation Effects Assessment Project Grazing Lands conservation practices on the Cienega Creek Watershed in southeast Arizona with RHEM/KINERSO2/AGWA modeling tools. Journal of Soil and Water Conservation. 75(3):304-318. https://doi.org/10.2489/jswc.75.3.304.
DOI: https://doi.org/10.2489/jswc.75.3.304

Interpretive Summary: The Conservation Effects Assessment Program was established to quantify the impacts of conservation spending by the USDA-Natural Resources Conservation Service (NRCS). An assessment was conducted on the Cienega Creek Watershed (CCW) in southeastern Arizona using ARS erosion and watershed modeling tools. Two types of data were used to derive model parameters. The first was from widely spaced NRCS field surveys across the larger major land resource area containing the CCW, as well as spatially explicit data obtained from remote sensing satellites. Periods of analysis and simulations of runoff and erosion were chosen for wet and dry climate conditions and periods with varying levels of conservation spending. Conclusions drawn from the widely spaced NRCS field survey and associated simulations could be interpreted as consistent when changing from a wet to dry period and the accumulation of conservation spending but cannot be used to assess the impacts of site-specific conservation practices. Data and simulations derived from remotely sensed data over known conservation practices such as mechanical brush removal and prescribed fires clearly indicated the positive effects of mechanical brush removal to reduce erosion but less so for prescribed burns. Results indicate that satellite data, when properly calibrated, has the potential to track the effects of the common rangeland conservation practice of brush removal over large areas.

Technical Abstract: A Conservation Effects Assessment Project (CEAP) was conducted on the Cienega Creek Watershed (CCW), located in southeastern Arizona, to investigate whether conservation practices improve watershed condition by examining changes in simulated runoff and sediment yield using ARS modeling tools with National Resources Inventory (NRI) sample data as well as remotely sensed data. Several periods of analysis based on climatic contrasts and conservation spending were selected. In addition, a 62 hectare watershed was modeled with parameters derived from remotely sensed data before and after brush treatment and with and without a stock pond. We found that the CCW simulations using NRI derived model parameters could be interpreted as consistent when changing from a wet to dry period and an accumulation of conservation spending but cannot be used to assess the impacts of site specific conservation practices as is possible with remote sensing. In the treated small watershed we found that remote sensing was capable of detecting and estimating the change in shrub cover from mechanical grubbing. Simulations of sediment yield using pre- and post-treatment data indicated a reduction in sediment yield but was modest in comparison to reductions from a stock pond. Remotely derived model parameters were then used in simulations of the entire CCW. Results clearly indicated the positive effects of mechanical brush removal but less so for prescribed burns.