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<br />. . <br /> <br />00273-4 <br /> <br />Opportunities for Ecological Improvement Along the Lower Colorado River <br />Mark Briggs and Steve Cornelius <br />7/24/97 <br /> <br />about 20,000 hectares (Glenn et al. 1996). As noted above, this cienaga offers habitat for <br />many wildlife species, including probably the largest populations of the endangered ' <br />Yuma clapper rails (Eddleman 1989; Abarca et al. 1993) and Sonoran desert pupfish <br />(Hendrickson and Verela 1989; Abarca et al. 1993). H the Yuma desalting plant begins <br />operation and the Wellton-Mohawk waters are diverted to irrigation dishicts in <br />Mexacali, the largest remaining wetland in the region will be significantly <br />compromised (Glenn et al. 1996; Zengel et al. 1995). Conservation efforts need to focus <br />on ways to maintain flow into the Cienaga. H the desalting plant does go on line, other <br />sources of water need to be found to make up for that lost to plant operations. Such <br />alternative waters could be found by allocating Colorado River water for ecosystem <br />maintenance or diverting agricultural return flows from Mexico southward. <br /> <br />Rio Hardy Wetlands <br />The Rio Hardy wetlands have experienced growth and decline over the past 50 years. <br />During the period of 1947 to 1983, the wetlands of the Rio Hardy were maintained by <br />water impounded behind an natural bar that existed roughly 35 km from the mouth of <br />the Colorado River (Payne et al. 1992). However, the bar was destroyed by the high <br />flows of 1983 and the resulting drainage reduced the size of the wetlands from 63,000 <br />ha in 1983 to 1,175 ha in 1988. High flows during 1992, however, have increased the <br />wetlands to 24,000 ha, but this increase is likely temporary if some type of <br />impoundment structure is not re-created (Glenn et al. 1996). <br /> <br />Conservation/ recovery efforts in the near future should focus on augmenting <br />agricultural return flows to the Rio Hardy wetlands and preventing waters from <br />escaping once they reach the wetlands. Ducks Unlimited engineers have recommended <br />repairing the natural dam that was destroyed by the flooding of 1983 (Payne et al. <br />1992). This strategy would probably reduce drainage from the Rio Hardy wetlands <br />and help to restore at least a portion of the former wetland area. Conducting a <br />feasibility study of this and similar strategies to maximize the environmental use of <br />waters entering these wetland areas should be a priority. <br /> <br />The Colorado-Gila River Confluence <br />The cottonwood-willow riparian forest at the confluence of the Colorado and Gila <br />Rivers is a product of natural riparian regeneration following the high flows of 1983 <br />and 1993. The expanse of this area demonstrates the often dramatic resiliency of these <br />wetland systems. Such natural regeneration also represents an important <br />restoration/ conservation opportunity. As in this case, nature has done the majority of <br />the ecological improvement work. Flooding has re-worked alluvial sediments to create <br />ideal seedbed conditions for riparian plants; and nearby riparian plants have <br />disseminated seed. <br /> <br />Future priorities should include identifying similar natural areas throughout the basin <br />and developing plans for their protection. As is the issue throughout the lower <br />Colorado River, "finding" the water required to maintain these areas is the key <br /> <br />Page 22 <br />