SS3.21 Deconstructing Rivers: The Ecological, Geomorphic, and Social Consequences of Dam Removal
Date: Thursday, June 13, 2002
Time: 10:30:00 AM
Location: Colwood
ShafrothPB, USGS Midcontinent Ecological Science Center, Fort Collins, USA,
Scott, M, L, USGS Midcontinent Ecological Science Center, Fort Collins, USA,
Auble, G, T, USGS Midcontinent Ecological Science Center, Fort Collins, USA,
Following dam removal, the vegetation that becomes established on the former reservoir bottom influences sediment transport downstream and site quality for use by humans and wildlife. Further, the bare substrates characteristic of exposed reservoir bottoms are at risk of being colonized by undesirable, exotic species. We studied vegetation establishment on the exposed bottom of Horsetooth Reservoir near Fort Collins, Colorado. Between January 2000 and October 2001, the water level was drawn down 32 m to enable dam repairs, exposing >550 hectares of substrate. Water levels are expected to remain low until early 2004. In September 2001, we measured the percent cover of all vascular plant species in 1516, 1 m2 quadrats along fourteen transects extending from the water's edge to the upland. We measured the elevation and substrate particle size distribution of each quadrat. We recorded >110 species, the most frequent of which were Chenopodium glaucum (45% frequency) and Panicum capillare (43% frequency). We relate the composition and distribution of plant species to the timing of draw down, elevation above the reservoir surface, and substrate particle size.