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<br />34
<br />
<br />J. C. STROMBERG
<br />
<br />Wunderlicli R.C., Winter, B.D. & Meyer, J.R. (1994). Restoration of the Elwha River ecosystem.
<br />Fisheries, 19: 11-19. .'
<br />Zamora-Arroyo, F., Nagler, P., Briggs, M.,. Radtke, !J., Rodr;quez, H., Garcia, J., Valdes, C.,
<br />Huete, A. & Glenn, E. (2001). Regeneranon ofnanve trees In response to ,flood ~eases from
<br />the United States into the delta of the Colorado River, Mexico. Journal of Arid EnVlTonments, 49:
<br />49-64. doi:l0.l006/jare.2001.0835.
<br />
<br />.1oumal of Arid Environments (2001) 49: 35-48
<br />doi:l0.l006/iare.2001.0834, available online at http://www.idealibrary,com on IDE~lQj)
<br />~
<br />
<br />~
<br />
<br />A preliminary water balance for the Colorado River
<br />delta, 1992-1998
<br />
<br />Michael}. Cohen*t, Christine Henges-}eck* & Gerardo
<br />Castillo-Morenot
<br />
<br />C-,
<br />c:;;.
<br />c...'"
<br />I" "',
<br />
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<br />
<br />*Pacific Institute for Studies z'n Development~ Environment~ and Security~
<br />654 13th Street, Oakland, California 94612~ U.S.A.
<br />tInstituto TecnolOgico y de Estudios Superiores de Monterrey/Campus
<br />Guaymas, Apartado Postal 484~ Guaymas~ Sonora 85400, Mexico
<br />
<br />Water balances for the Colorado River mainstem complex, the Cienega de
<br />Santa Clara, and Ellndio wetlands were calculated for the Colorado River delta
<br />in Mexico for the period 1992-1998. Discharge for the mainstem complex was
<br />disaggregated into flood and non-flood years, reflecting the marked variability
<br />of mainstem discharge at the Southerly International Boundary (Sm) delimit-
<br />ing the United States and Mexico, In non-flood years, agricultural and munici-
<br />pal returns to the mainstem below SIB contributed 180% of mainstem
<br />discharge at SIB, but may not be sufficient to generate the floodstage
<br />discharge required by native riparian vegetation.
<br />
<br />@ 200 I Academic Press
<br />
<br />Keywords: Colorado River delta; water balance; hydrology; agricultural
<br />drainage; riparian vegetation; wetland vegetation
<br />
<br />Introduction
<br />
<br />The delta of the Colorado River, a remnant wetland located along the border of
<br />the Mexican states of Baja California and Sonora, is the subject of growing scientific and
<br />political interest. The recent literature on the ecology and restoration of the delta of
<br />the Colorado River emphasizes the importance of natural and anthropogenic sources of
<br />water for sustaining delta habitats (Glenn et al., 1992, 1996, 1999; Zengel et ai.,
<br />1995; Morrison et ai., 1996; Valdes-Casillas et ai., 1998; Luecke et ai., 1999; Pitt et ai.,
<br />2000).
<br />The delta, fonned by the deposition of sediment from periodic Colorado River floods
<br />(Sykes, 1937) has been altered by the construction of upstream impoundments and the
<br />conversion of wetlands to irrigated agriculture, reducing the delta's extent from some
<br />7770 km2 to 600 km2 (Luecke et ai., 1999). Prior to the construction of dams, diver-
<br />Nions, and other reclamation projects, the mean annual discharge of the Colorado River
<br />water near Lees Ferry, Arizona, 1067 km upstream of the current extent of the delta, has
<br />been estimated at 17,000 x 106m3 (l7km3) (Meko et ai., 1995). Before upstream
<br />impoundments and diversions dewatered the Gila River, it contributed an estimated
<br />
<br />t Corresponding author,
<br />
<br />'i 0140-1963/01/090035 + 14 535.00/0
<br />
<br /><C> 200 1 Academic Press
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