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<br />4
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<br />E. P. GLENN ET AL.
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<br />References
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<br />Glenn, E., Lee, R.C., Felger, R. & Zengel, S. (1996). Effects of water management on the
<br />wetlands of the Colorado River Delta, Mexico. Conservation Biology, 10: 117 5-1186. ~,
<br />Leopold, A. (1949). The green lagoons. In Leopold, A. (Ed.) A Sand County AlmanlU: .~
<br />pp. 150-158. New York: Oxford University Press, 226 pp. I,".'.'
<br />Sykes, G. (1937). The Colorado Delta. Washington, D.C. Carnegie Institution. 193 PP'I
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<br />Journal of Arid Environmenu (2001) 49: 5-15 II>
<br />doi:IO,1006/iare.2001.0832, available online at http://www.idealibrary.com on IDE~l
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<br />Ecology and conservation biology of the Colorado
<br />River Delta, Mexico
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<br />Edward P. Glenn*, Francisco Zamora-Arroyot, Pamela L. Nagler*,
<br />Mark Briggs:!:, William Shaw~ & Karl F1essa~
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<br />*Environmental Research lAboratory, 2601 East Airport Drive,
<br />Tucson, AZ 85706 U.SA.
<br />fConservation International, Guaymas, Mexico
<br />tRincon and $r,moran Ins#tute, Tucson, AZ, U.SA.
<br />gWildlife and Fisheries Program, University of Arizona, Tucson, AZ, U.sA.
<br />1fDepartment of Geosciences, University of Arizona, Tucson, AZ, U.S.A.
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<br />The Colorado River delta in Mexico has been partially revegetated following
<br />20 years of water flows from the United States. Lake Powell, the last major
<br />impoundment built on the river, filled in 1981. Since then, flood flows in the
<br />main channel of the river have occurred inEl Niiio cycles, and have returned
<br />native trees and other vegetation to the riparian corridor. This vegetation
<br />provides a migration route for endangered southwestern willow flycatchers
<br />(Empidonax traillii) and other migratory birds moving from Mexico to the
<br />United States for summer nesting. Agricultural drain water from the Wellton-
<br />Mohawk Irrigation District conveyed to the delta since 1977 has created
<br />Cienega de Santa Clara, a 4200-ha Typha domengensis marsh containing the
<br />largest remaining population of the endangered Yuma clapper rail (Rtdlus
<br />longirostris yumanensis), plus numerous species of migratory and resident
<br />waterfowl. Populations in the marine part of the delta have been severely
<br />'affected by the lack of river flow, but some species have responded
<br />positively to renewed flows. Currently, there are 170,000 ha of natural areas in
<br />the lower delta in Mexico, containing riparian, wetland and intertidal habitats.
<br />Much of this land as well as the adjacent marine zone is protected in the
<br />Biosphere Reserve of the Upper Gulf of California and Colorado River Delta.
<br />Natural resource managers, scientists and non-governmental environmental
<br />groups in Mexico and the United States are exploring conservation measures
<br />that can provide water and protection for these areas for the future.
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<br /><<:> 2001 Academic Press
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<br />Keywords: Colorado River; El Nino; delta; Biosphere Reserve; estuary; ripar-
<br />ian; wetland; desert river
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<br />Introduction
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<br />Riparian corridors are critical habitat for desert flora and fauna, providing oases of
<br />species diversity and high productivity in otherwise dry environments (Poff et aI.,
<br />1997). They are also critical routes for migratory birds passing through desert regions on
<br />their way to nesting or wintering grounds. The lower Colorado River from Grand
<br />Canyon to the Gulf of California provides the greatest acreage of riparian and wetland
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<br />01 4Q.. 1 963/0 1/090005 + 11 535.00/0
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<br />iC 2001 Academic Press
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