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<br />002728 <br /> <br />Opportunities for Ecological Improvement Along the Lower Colorado River <br />Mark Briggs and Steve Cornelius <br />7/24/97 <br /> <br />times of high flow. The Rio Hardy wetlands are dominated by halophytic plants such <br />as iodine-bush (Allenrolfea occidentalis), quail-brush (Atriplex lentiformis), and Salicornia <br />verginiea. Ground cover includes saltgrass and alkali weed; and less salt-tolerant plants <br />such as aITowweed (Pluchea sericea) and desert broom (Baccharis emoryl). <br />Conseroation Challenges: The vegetation of this area has changed significantly since the <br />turn. of the century. As described by McDougal (1904), this area was dominated to the <br />north by a riparian forest of cottonwoods (Populus fremontil) and willow (Salix <br />gooddingii) with an extensive tidal-influenced plain of saltgrass (Distichlis spicata) at its <br />southern end. In between there were scattered mesquite trees (Prosopis spp.) and <br />saltbushes (Atriplex spp.). Today, the riparian forest is no longer present and the <br />wetland is dominated for the most part by halophytic plants (Glenn et ale 1996). From <br />at least 1977 to 1983 the Rio Hardy wetlands were maintained by ponded waters <br />behind a natural dam (Glenn, pers. comm. 1997). The destruction of the dam during <br />high flow events of 1983 has caused the wetlands to drain and generally decline (Payne <br />et al. 1992), although large flows during 1992 and 1993 caused the wetland area to <br />increase from a low of 1,175 hectares in 1988 to 24,000 hectares in 1993 (Glenn et al. <br />1996). <br />Lessons Learned: The earthen dam that was destroyed by the floods of 1983 needs to be <br />re-constructed. Such a strategy is relatively simple and inexpensive, yet could <br />significantly increase the current area occupied by the Rio Hardy wetlands (Payne et ale <br />1992). Indeed, the Cocopah people have already initiated construction of a replacement <br />dam close to where the original dam was located (Edward Glenn, pers. comm., 1997). <br /> <br />Site #12 <br />Cienaga de Santa Oara <br />Location and Size: The cienaga is located on the eastern side of the delta and covers <br />roughly 20,000 hectares, with 4,500 hectares thickly vegetated. <br />Ecological Characteristics: In total there are 22 wetland plants in and along the periphery <br />of the cienaga. The main portion of the cienaga is dominated by T. domengensis and at <br />least eight other hydrophytes (Glenn et al. 1996). It is supported principally by <br />agricultural runoff from the Wellton-Mohawk canal, with lesser inputs from the Riito <br />Drain. <br />Conseroation Challenges: The principal conservation challenge facing the cienaga is the <br />possibility that the Well ton-Mohawk canal will be turned off. The Well ton-Mohawk <br />canal was planned as a temporary answer for agricultural wastewater deposition until <br />the de-salinization plant went on line. Although the Santa Clara system is also <br />supported by waters emanating from the Riito Drain, flow in the Wellton-Mohawk can <br />is much greater and therefore more crucial. If this source of water is indeed turned off, <br />a significant portion of the cienaga will be compromised. In addition, the cienaga faces <br />challenges from the invasion of exotic plants and increasing high levels of salinity. <br />Lessons Learned: The U.S. Department of the Interior needs to make a long-term <br />commitment to providing Well ton-Mohawk waters to the cienaga. There should also <br />be consideration to directing more Uwastewater" (flood water, effluent, and <br /> <br />Page 16 <br />