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Research Project: Understanding Water-Driven Ecohydrologic and Erosion Processes in the Semiarid Southwest to Improve Watershed Management

Location: Southwest Watershed Research Center

Title: An ecohydrological stream type classification of intermittent and ephemeral streams in the Southwestern United States

Author
item Levick, L.r. - University Of Arizona
item Hammer, S. - University Of Arizona
item Lyon, R. - University Of Arizona
item Murray, J. - Colorado State University
item Birtwistle, A. - Colorado State University
item Guertin, D.p. - University Of Arizona
item Goodrich, David - Dave
item Bledsoe, B. - Colorado State University
item Laituri, M. - Colorado State University

Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2018
Publication Date: 3/5/2018
Citation: Levick, L., Hammer, S., Lyon, R., Murray, J., Birtwistle, A., Guertin, D., Goodrich, D.C., Bledsoe, B., Laituri, M. 2018. An ecohydrological stream type classification of intermittent and ephemeral streams in the Southwestern United States. Journal of Arid Environments. 155:16-35.
DOI: https://doi.org/10.1016/j.jaridenv.2018.01.006

Interpretive Summary: Ephemeral and intermittent streams are the predominant fluvial forms in arid and semi-arid environments. Various studies have shown biological and habitat diversity in these lands to be considerably higher along stream corridors in comparison to adjacent uplands, yet knowledge of how these streams function is limited. An ecohydrological stream type classification was developed to improve decision making for four military reservations in the southwestern U.S.: Fort Irwin, Yuma Proving Ground, Fort Huachuca, and Fort Bliss. Cluster analysis was used to classify stream systems by ecohydrologic properties (vegetation, hydrologic, and geomorphic attributes) using Classification and Regression Tree analysis to determine thresholds for each of these variables for a predictive model. The Automated Geospatial Watershed Assessment (AGWA) tool with the ARS KINEROS2 and SWAT watershed models was used to evaluate impacts of climate change, training activities, and land management actions on flow permanence and runoff peak flows of individual stream reaches. The final stream types were determined from statistical and cluster analyses and site knowledge. Climate regime and geomorphology were most important for Yuma Proving Ground and Fort Irwin where annual rainfall amounts are relatively low or largely confined to one season per year. Vegetation variables were more important at Fort Bliss and Fort Huachuca that exhibit higher annual rainfall amounts and a bimodal annual rainfall pattern.

Technical Abstract: Ephemeral and intermittent streams are the predominant fluvial forms in arid and semi-arid environments. Various studies have shown biological and habitat diversity in these lands to be considerably higher along stream corridors in comparison to adjacent uplands, yet knowledge of how these streams function is limited. An ecohydrological stream type classification was developed to improve decision making for four military reservations in the southwestern U.S.: Fort Irwin, Yuma Proving Ground, Fort Huachuca, and Fort Bliss. Agglomerative hierarchical cluster analysis was used to classify stream systems by ecohydrologic properties (vegetation, hydrologic, and geomorphic attributes), and CART was used to determine thresholds for each variable for a predictive model. The Automated Geospatial Watershed Assessment tool was used to evaluate impacts of climate change, training activities, and land management actions on flow permanence and peak flows. The final stream types were determined from statistical analyses, cluster validity tests, examination of mapped clusters, and site knowledge. Climate regime and geomorphology were most important for YPG and Fort Irwin where annual rainfall amounts are relatively low or largely confined to one season per year. Vegetation variables were more important at Fort Bliss and Fort Huachuca with higher annual rainfall amounts and a bimodal pattern.