THE IMPACTS OF EPHEMERAL GULLY EROSION AT NEAL SMITH NATIONAL WILDLIFE REFUGE

Soil productivity is decreased and nutrients are lost when soil is eroded by water, a serious concern in intensive row-cropped agricultural landscapes (Helmers et al, 2012). And, lost sediment is a non-point source of pollution for surface waters (Helmers et al, 2012). There is a need to conduct research to understand how to properly manage agricultural land to prevent degradation downstream. Gully erosion is defined as “the erosion process whereby runoff water accumulates and often recurs in narrow channels and, over short periods, removes the soil from narrow areas to considerable depths” (Poesen et al, 2012). The study conducted at Neal Smith National Wildlife Refuge quantified soil loss for all ephemeral gully erosion in 12 agricultural watersheds in June 2012. Cross sections of gullies were surveyed every meter using a rill meter. Gully erosion from those watersheds was also measured in November 2011 covering four years of undisturbed soil (2007-2011). The purpose of this research was to compare collected data in November 2011 to data from June 2012 and to look at the contribution of soil loss from gully erosion in comparison to the total sediment in runoff. Two factors altered June 2012 data: the gullies were filled March 26, 2012, rainstorms immediately followed, and the 2012 growing season has received little rainfall. The results suggested a linear relationship between total sediment loss and gully erosion with measured sediment in runoff water. Results also suggested that the gullies in June 2012 are eroding to their state in November 2011. This has implications for different land use practices: grassed waterways, vegetation cover, natural vegetation, and no tillage. Once soil disturbance is minimized, soil erosion will be decreased. These practices will ensure the maintenance of soils and agricultural yield, despite future impacts of climate change.

References

Helmers, M.J., Zhou, X., Asbjorsen, H., Kolka, R., Tomer, M.D., and Cruse, R.M. 2012. Sediment Removal by Prairie Filter Strips in Row-Cropped Ephemeral Watersheds, Journal of Environmental Quality. Pages 1-8, DOI: 10.2134/jeq2011.0473.

Poesen, J., Nachtergaele, J., Verstraeten, G., and Valentin, C. 2003. Gully erosion and environmental change: importance and research needs, Catena. Pages 91-123.