Skip to main content
ARS Home » Pacific West Area » Reno, Nevada » Great Basin Rangelands Research » Research » Publications at this Location » Publication #342271
Title: Mapping Erosion and Salinity Risk Categories Using GIS and the Rangeland Hydrology Erosion Model

Author
item MCGWIRE, KENNETH - Desert Research Institute
item FOUNDS, MICHAEL - Desert Research Institute
item Weltz, Mark
item NOUWAKPO, SAYJRO - University Of Nevada

Submitted to: World Conference Soil and Water Conservation Under Global Change (CONSOWA)
Publication Type: Proceedings
Publication Acceptance Date: 5/25/2017
Publication Date: 6/12/2017
Citation: Mcgwire, K.E., Founds, M., Weltz, M.A., Nouwakpo, S.K. 2017. Mapping Erosion and Salinity Risk Categories Using GIS and the Rangeland Hydrology Erosion Model. World Conference Soil and Water Conservation Under Global Change (CONSOWA). 199.

Interpretive Summary: Up to fifteen percent of rangelands in the state of Utah in the United States are classified as being in severely eroding condition. Some of these degraded lands are located on saline, erodible soils of the Mancos Shale formation. This results in a disproportionate contribution of sediment, salinity, and selenium to the Colorado River which is a critical water resource for both the United States and Mexico. Prior work has documented a significant linear relationship between salinity and sediment in the runoff from experimental rainfall simulator plots on the Mancos Shale. Land management agencies in the U.S. are considering mitigation activities to reduce erosion on these saline rangelands, and an initial question is how to prioritize different locations for action. Classification of GIS variables associated with soil erosion and salt transport processes with an unsupervised clustering routine like ISODATA provides a useful way of characterizing general patterns of erosion risk across the landscape. To ensure that the algorithm’s parameters are appropriate, it is useful to visualize the distribution of the clustered classes within the data space. Having reduced the complexity of a large landscape to a limited number of classes, it is possible to estimate relative levels of risk using a plot-scale erosion model. The resulting risk map can help to ensure that planned mitigation activities are cost-efficient and target the most serious risks to sustainability.

Technical Abstract: Up to fifteen percent of rangelands in the state of Utah in the United States are classified as being in severely eroding condition. Some of these degraded lands are located on saline, erodible soils of the Mancos Shale formation. This results in a disproportionate contribution of sediment, salinity, and selenium to the Colorado River which is a critical water resource for both the United States and Mexico. Prior work has documented a significant linear relationship between salinity and sediment in the runoff from experimental rainfall simulator plots on the Mancos Shale. Land management agencies in the U.S. are considering mitigation activities to reduce erosion on these saline rangelands, and an initial question is how to prioritize different locations for action. Classification of GIS variables associated with soil erosion and salt transport processes with an unsupervised clustering routine like ISODATA provides a useful way of characterizing general patterns of erosion risk across the landscape. To ensure that the algorithm’s parameters are appropriate, it is useful to visualize the distribution of the clustered classes within the data space. Having reduced the complexity of a large landscape to a limited number of classes, it is possible to estimate relative levels of risk using a plot-scale erosion model. The resulting risk map can help to ensure that planned mitigation activities target the most serious risks and are not overly biased by prior expectations.