Recent vegetation changes along the Colorado River between Glen Canyon Dam and Lake Mead, Arizona

Abstract

Introduction ____________________________________ 1 Acknowledgments ____________________________________ 3 Changes in Colorado River streamflow regime ________ 3 Floods _________________________________ 3 Daily stage.__________________________ 6 Annual discharge_________________________ 7 Monthly discharge __________ _______________________? Changes in channel and alluvial deposits in the Colorado River below Glen Canyon Dam ______________________ 8 A history of photography on the Colorado River __________ 10 Vegetation _______________________________________12 Distribution of major plant species ___________________13 Bermuda grass ________________________________14

Site-Occupancy Monitoring of an Ecosystem Indicator: Linking Characteristics of Riparian Vegetation to Beaver Occurrence

“…For instance, in the Grand Canyon, the beaver population has likely increased since the construction of Glen Canyon Dam, putatively because controlled flows from the dam beginning in 1963 led to higher primary and secondary production in riparian ecosystems (Turner andKarpiscak 1980, Kearsley et al 2006). Numerous studies have shown that riparian vegetation has increased in the Grand Canyon since flow regulation primarily because of the elimination of annual flood events that scoured shorelines (Turner and Karpiscak 1980, Stevens et al 1995. For instance, the area of riparian vegetation has increased by more than 50% and continues to expand , and marsh communities have expanded throughout the corridor (Stevens et al 1995).…”

Origin of the Colorado River experimental flood in Grand Canyon

“…However, the existence and operation of Glen Canyon Dam had additional incidental, though very significant, physical and ecological effects upon the Colorado River downstream through Grand Canyon National Park, Both the aquatic and riparian communities have been substantially altered by the invasion of exotic species more adapted to colder, clearer water and less variable flows than the native species (Turner & Karpiscak, 1980;Minckley, 1991). These issues and others are discussed extensively in Marzolf (1991).…”

The Biogeographic Significance of a Large, Deep Canyon: Grand Canyon of the Colorado River, Southwestern USA

“…Thus, unlike alluvial rivers, the location of sandbars in the geomorphically constrained Colorado River are fixed within 13 geomorphic reaches (Table 2). More than 550 debris fan complexes generate a distinctive suite of fluvial microhabitats, each with discrete grain sizes, soils, stage elevation relationships, inundation frequencies, and stage-zoned riparian vegetation (Turner and Karpiscak 1980;Schmidt and Graf 1990;Melis et al 1997). Analyses of flow regulation influences at a large suite of debris fan complexes revealed that flow regulation allowed extensive development of fluvial marshes, enhancing riverine plant species richness (Stevens et al 1995;Waring et al in press).…”