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<br />002727 <br /> <br />Opportunities for Ecological Improvement Along the Lower Colorado River <br />Mark Briggs and Steve Cornelius <br />7/24/97 <br /> <br />were placed around some plants to protect against beaver damage (Pinkney 1992). <br />Plants were irrigated each day in 1985 from planting to September. Afterwards, <br />irrigation was cut off until May 1986 when the trees began to appear stressed. Daily <br />watering at the same rate began and continued to September 1986. After September, <br />the rate was decreased to three gallons per day. <br />Results: Two years following the completion of the revegetation work, approximately <br />30 percent of the trees had died. In 1988, more than 70 percent of the cottonwoods and <br />willows along the edge of the pond were over three meters tall; some of the trees along <br />the outlet channel and the edge of the pond were six meters tall or more. By 1997, <br />many of the trees were over 10 m (35 ft) tall and appeared to be growing vigorously. <br />Lessons Learned: Results underscore the need to clarify project objectives. In this case, it <br />is difficult to evaluate whether revegetation results actually mitigated for disturbances <br />caused by the construction of the de-salinization plant Without additional detail put <br />into developing the objective further, such a determination is difficult if not impossible <br />to answer. <br /> <br />Site #10 <br />Colorado River-Gila River Confluence <br />Location and Size: This is a naturally vegetated site at the confluence of the Colorado <br />and Gila Rivers, just downstream from Prison Hill in Yuma, Arizona. The site is <br />situated along four kilometers of the West Main Colorado River canal and encompasses <br />over 80 hectares (200 acres). <br />Ecological Characteristics: Most of the vegetation here appears to have come up <br />following the high magnitude flows of 1993 and 1994, although large cottonwood trees <br />along the southern portion of the site probably came up following the floods of 1983. <br />Further work is required to develop a detailed description of this site's current <br />ecological characteristics and the degree that is has changed since 1983. Nevertheless, it <br />is apparent that significant natural regeneration took place and contains an extensive <br />riparian fo.rest that consists of such native species as Fremont cottonwood, Goodding <br />Willow, mesquite, seep willow (Baccharis glutinosa), and cattail. <br />Conservation Challenges: Taking advantage of nature's efficacy by allocating waters to <br />wetland plant communities that develop following large flow events could be an <br />effective way of maintaining significant wetland habitat along the river. As is the case <br />throughout much of the lower Colorado River, however, acquiring water of sufficient <br />quantity and quality for maintaining such critical native wetland habitat is one of the <br />critical conservation challenges. <br /> <br />Site #11 <br />Rio Hardy Wetlands <br />Location and Size: The Rio Hardy wetlands are in the Colorado River delta on one of the <br />western most branches of the river (Fig. 2). <br />Ecological Characteristics: Flow into the Rio Hardy comes principally from agricultural <br />runoff and geothermal wells discharged into the channel (Payne et al. 1992). A <br />potential third source is backflow from the mainstem of the Colorado River during <br /> <br />Page 15 <br />