HR: 18:05h
AN: H44A-08    [Abstracts]
TI: A Water Budget for Riparian Vegetation on the Lower Colorado River: the Myth of Water Salvage
AU: Nagler, P L
EM: pnagler@ag.arizona.edu
AF: University of Arizona, School of Natural Resources, 125 Biological Sciences East, Tucson, AZ 85721, United States
AU: * Glenn, E P
EM: eglenn@ag.arizona.edu
AF: University of Arizona, Soil, Water, and Environmental Science Dept., 2601 E. Airport Drive, Tucson, AZ 85706, United States
AU: Webb, R H
EM: rhwebb@usgs.gov
AF: U.S. Geological Survey, WRD, 520 N. Park Avenue, Tucson, AZ 85719, United States
AU: Howard, K A
EM: khoward@usgs.gov
AF: U.S. Geological Survey, MS 973, Menlo Park, CA 94025, United States
AB: For many years, river managers have envisaged large saving of water by clearing the exotic plant, saltcedar (Tamarix ramosissima) from western U.S. rivers. Early estimates of evapotranspiration (ET) by saltcedar ranged as high as 3-4 m/yr, and it was estimated that saltcedar on the Lower Colorado River used more water than Los Angeles. Furthermore, saltcedar was considered to have low habitat value, so clearing projects might enhance habitat value by allowing the return of more valuable native species. We have examined these assumptions based on recent evidence. Moisture flux towers set in dense saltcedar stands show that ET is moderate, ranging from 0.8-1.4 m/yr with a mean value of 1 m/yr over five studies on three rivers, similar to wide-area estimates from remote sensing studies. Projected over the 18,200 ha of dense saltcedar monocultures estimated for the Lower Colorado River riparian corridor in the U.S., the potential water saving would only be about 1 percent of the annual flow (assuming no replacement vegetation). A similar acreage of saltcedar monoculture exists in the Colorado River delta in Mexico, but these stands are supported by outflow of brackish water from the irrigation district rather than river water. The assumption of low habitat value is not supported by recent studies. For example, Hinojosa- Huerta (2006) found that saltcedar monocultures away from the river channel supported 65 percent as many bird numbers and 74 percent as many bird species as the best habitat type, mixed saltcedar and native trees in proximity to water, in the delta of the Colorado River in Mexico, and saltcedar provided equal habitat value as native trees for endangered willow flycatchers on Arizona and New Mexico rivers (Owen et al., 2005). Hence, the prospects for saving water without destroying habitat by clearing saltcedar are doubtful for this river system.
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
DE: 1813 Eco-hydrology
DE: 1825 Geomorphology: fluvial (1625)
DE: 4815 Ecosystems, structure, dynamics, and modeling (0439)
SC: Hydrology [H]
MN: 2007 Joint Assembly