Modeling climate change effects on runoff and soil erosion in southeastern Arizona rangelands and implications for mitigation with rangeland conservation practices

Authors: ZHANG, Y. - University Of Arizona; HERNANDEZ, M. - University Of Arizona; Anson, Eric; Nearing, Mark; WEI, H. - University Of Arizona; Stone, Jeffry; Heilman, Philip - Phil

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2011
Publication Date: 9/1/2012
Citation: Zhang, Y., Hernandez, M., Anson, E.L., Nearing, M.A., Wei, H., Stone, J.J., Heilman, P. 2012. Modeling climate change effects on runoff and soil erosion in southeastern Arizona rangelands and implications for mitigation with rangeland conservation practices. Journal of Soil and Water Conservation. 67(5):390-405. https://doi.org/10.2489/jswc.67.5.390.
DOI: https://doi.org/10.2489/jswc.67.5.390

Interpretive Summary: Climate change is expected to change precipitation patterns in the southwestern United States. This study was done to evaluate the potential impacts of precipitation changes on soil erosion and surface water runoff in southeastern Arizona that will occur as a result of rainstorms. We used the outputs from seven models of climate change for the projected time periods of the 2050s and 2090s in order to run a model to assess what these changes might be compared to 1970 through 1999 conditions. We used a USDA-ARS model called the Rangeland Hydrology and Erosion Model (RHEM). Our results suggested no significant changes in annual precipitation across the region, but projected mean annual runoff and soil loss approximately doubled. These dramatic increases in runoff and soil loss were attributed to the increase in the frequency and intensity of extreme events. Predicted erosion from shrub communities increased more than that for other plant communities under the three scenarios. This may be a problem, because future increasing runoff and soil erosion could accelerate the transitions of grassland to shrublands or to more eroded states that has already been occurring on the area over the past century. Rangeland management policies and practices should consider these possible changes and adapt to the increased risk of runoff and soil erosion under a changing climate.

Technical Abstract: Climate change is expected to impact runoff and soil erosion on rangelands in the southwestern United States. This study was done to evaluate the potential impacts of precipitation changes on soil erosion and surface runoff in southeastern Arizona using seven GCM models with three emission scenarios for the 2050s and 2090s. A spatial- temporal downscaling process was used to generate daily precipitation series from GCM outputs for runoff and erosion modeling with the Rangeland Hydrology and Erosion Model (RHEM). Results were compared to 1970 through 1999 conditions. Our results suggested no significant changes in annual precipitation across the region under the three scenarios, while projected mean annual runoff and soil loss increased significantly, ranging from 79% to 92% and from 127% to 157%, respectively, relative to 1970-1999. At the seasonal scale, though an increase of summer precipitation and a reduction of winter precipitation were projected, both runoff and soil loss increased significantly for both periods. The dramatic increases in runoff and soil loss were attributed to the increase in the frequency and intensity of extreme events in the study area. Predicted soil loss from shrub communities increased more than that for other plant communities under the three scenarios. Future increasing runoff and soil erosion may accelerate the transitions of grassland to shrublands or to more eroded states due to the positive vegetation-erosion feedback. Rangeland management policies and practices should consider these changes and adapt to the increased risk of runoff and soil erosion.