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<br />48
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<br />M. J, COHEN ET AL.
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<br />Sykes. G, (1937), The Colorado Della. Publication no. 460. Washington, DC: Carnegie Institu-
<br />
<br />tion. 193 pp. C I d R.
<br />U.S. Bureau of Reclamation. (1952). Report on the Water Supply of the Lower 0 ora 0 lVer.
<br />Project Planning Report. November.. , .
<br />U.S. Bureau of Reclamation. (1997). Lnwer Colomdo River Accollnllllg System Dell!OltStl'allOn of
<br />Technology Calendar Year 1997. Boulder City, Nevada: Lower Colorado Regional Office,
<br />March. 47 pp. plus attachments, .' .
<br />U.S. Bureau of Reclamation. (1998). Lower Colorado RIVer AccOlllllmg System Dell!oltsttalWIt of
<br />Technology Calendar Year 1998, Boulder City, Nevada: Lower Colorado Regional Office,
<br />March, 48 pp. plus attachments... .
<br />Valdes-Casi\1as C Hinojosa-Huerta, 0., Munoz-Viveros, M., Zamora-Arroyo, F" Carnllo-
<br />Guerrero, y:, D~lgado-Garcia, S., Lopez-Camacho, M., Glenn, E,P., Garcia, J., Riley, J.,
<br />Baumgartner, D., Briggs, M., Lee, C,T., Chavarria-Correa, E., Congd~n, C, & Luecke, p.
<br />(1998). lnfonnaliolt Database and Lacal Ol/l.reacl~ Pro~/"ClJ/l fo~ the RestoTCI!,IOII of the Hardy R,ver
<br />U'letlamls. l.mver Colorado River Della, B,!ia Cal((0l7llCl and Sonom.. MeXICO. Guaymas, Sonora,
<br />Mexico: Institutl) Tecnologico Y de Estudios Superiores de Monterrey (ITESM), Campus
<br />Guaymas. 102 pp, . .. ,.
<br />Zamora-Arroyo, F., Hinojosa-Huerta, 0" Glenn, E., & Brlggs',M. (2001). Veg~tatLon.trends m
<br />responSe to instream flows in the Colorado River Delta, MeXICO. Journal of And EIlVll'o/1II1eIllS,
<br />49: 49-64. doi: 1 0.1 006/jare.2001.0835.
<br />Zengel, S" Mertetsky, V., Glenn, E., Felger, R., & Ortiz: D. (1995). .Cien~g~\ ,de ~anta Clara,
<br />a remnant wetland in the Rio Colorado delta (MeXICO): vegetation dlstnbutlon and the
<br />effects of water flow reduction. Ecological Engirleenng, 4: 19-36.
<br />
<br />.101117101 of Arid E'IlVimlllllents (2001) 49: 49-64
<br />doi:IO.1006Iiare,200l.0835, available online at http://www.idealibrary.com on IDE~lo~
<br />II-
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<br />@
<br />
<br />Regeneration of native trees in response to flood
<br />releases from the United States into the delta of the
<br />Colorado River, Mexico
<br />
<br />C:;".
<br />C'-,
<br />W
<br />1:'"
<br />
<br />CJ1
<br />
<br />Francisco Zamora-Arroyo*t, Pamela L. Naglertt, Mark Briggs*,
<br />Dean Radtke~, Hugo Rodriquez~, ]aqueline Garcia'[, Carlos V aldes*,
<br />Alfredo Huete~, Edward P. Glenn~
<br />
<br />*Instituto Tecnologico y de Estudios Superiores de Monten'ey, Bahia de
<br />Bacochibampo, Postal 484, Guaymas, Sonora 85400, Mexico
<br />tUniversity of Arizona, Soil, Water and Environmental Science Dept.,
<br />Ten'estrial Biophysics and Remote Sensing Lab, Tucson, AZ 85721 U.S.A.
<br />*Sonoran and Rincon Institute, 7650 E. Broadway, Suite 203, Tucson,
<br />AZ 85710 U.S.A.
<br />11 Environmental Research Laboratory of the University of Arizona, 2601 E.
<br />Airport Drive, Tucson, AZ 85706 U.S.A.
<br />
<br />Over the past 20 years, discharge of water from the United States to the delta of
<br />the Colorado River in Mexico has regenerated native trees that now account for
<br />23% of vegetation in a 100-km, non-perennial, stretch of river below Morelos
<br />Dam at the United States-Mexico border. The discharges are associated with
<br />the filling of Lake Powell, the last large reservoir to be constrUcted on the river,
<br />and with ENSO cycles that bring extra winter and spring precipitation to the
<br />watershed. The discharges below Morelos Dam produce overbank floods that
<br />germinate new cohorts of Populus ftvltll/llItii and Salix gooddingii trees. Relative-
<br />ly little flood water from tlle United States is required to support a pulse flood
<br />regime that can result in regrowtl1 of native vegetation in the delta. Based on
<br />analysis of past flows and existing tree populations, we estimate that a Febru-
<br />ary-April flow of 3 x 10' m3 at 80-1201l1" s - I is sufficient to germinate
<br />and establish new cohorts of native trees, Hl)wever, there was a positive
<br />correlation between frequency of flows and total vegetation cover over the
<br />years 1992-1999, showing that more frequent flows would further increase
<br />vegetation cover. The results support the importance of pulse floods in restor-
<br />ing the ecological integrity of arid-zone rivers.
<br />
<br />if: 2001 Academic Press
<br />
<br />Keytt'ords: EI Nino/ENSO; riparian; wetland; flood flows; native plants
<br />
<br />Introduction
<br />
<br />Most of the world's large rivers have been harnessed for human use; dams, water
<br />diversions, and flow regulation to control flooding have disrupted the natural ecology of
<br />
<br />tThese authors contributed equally to the work and should both be considered as senior I\uthofs.
<br />
<br />0140-1963101/090049 + 16 535.00/0
<br />
<br />II) 2001 Acadclllk 1'1'\'",
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