Cottonwood evaluation following environmental flow implementation along the Waterton River, Alberta

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Foster, Stephen
University of Lethbridge. Faculty of Arts and Science
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Lethbridge, Alta : University of Lethbridge, Dept. of Biology
Alberta’s Waterton River was dammed in 1964 and to avoid a collapse of downstream riparian woodlands as had occurred along the nearby St. Mary River, an Environmental Flow regime was implemented in 1991. This involved an increase in the minimum flow and flow ramping, gradual recession after spring peaks. This study assessed the consequences on the riparian woodlands by analyzing aerial photographs and assessing hydrological changes. Additionally, field research confirmed the persistence of the cottonwoods and quantified their growth characteristics through analyses of tree rings. Riparian cottonwood area remained relatively unchanged throughout the study interval, indicating survival after damming. There has been progressive colonization after damming, cottonwood growth benefitted from the Environmental Flow regime and analyses indicated that the increase in minimum flow was particularly beneficial.
cottonwood health , minimum flow criterion , ramping flows , riparian , river management