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<br />l <br /> <br />002717 <br /> <br />Opportunities for Ecological Improvement Along the Lower Colorado River <br />Mark Briggs and Steve Cornelius <br />7/24/97 <br /> <br />chinensis), arrowweed (Pluchea sericea), and iodine-bush (Allenrolfea occidentalis) <br />Freshwater and brackish habitat still remain, but these areas are confined for the most <br />part to agricultural wastewater discharge points, artesian springs, and areas influenced <br />by tidal fluctuations. <br /> <br />Despite the tremendous changes that have occurred in the Colorado River delta, it is <br />important to emphasize that the delta is not a dead ecosystem. Particularly during the <br />last decade, considerable amounts of Colorado River water have reached the delta, <br />helping to maintain several key intertidal, brackish, and riparian wetlands south of the <br />agricultural fields (Glenn et al. 1992, Payne et al. 1992). <br /> <br />In the delta, as well as the mainstem, significant marsh wetlands still exist Marshes are <br />a critical component of the lower Colorado River ecosystem and are dominated by soft- <br />stemmed emergent plants such as cattails (Typha spp.), bulrushes (Sdrpus acutus), and <br />phragmites (Phragmites australis) and frequently occur next to terrestrial and aquatic <br />habitats. Marsh habitat is critical to a plethora of bird species, including waterbirds <br />such as the western grebe (Aechmophorus occidentalis), double-crested cormorant <br />(Phalacrocorax auritus), and gadwall (Anas strepera); shorebirds such as the killdeer <br />(Charadrius vodferus), long-billed curlew (Numenius american us), and sandpipers <br />(Calidris spp.); and wading birds such as the green heron (Butorides striatus), roseate <br />spoonbill (Ajaia ajaja), and the endangered Yuma dapper rail (Rallus longirostris). <br /> <br />The principal wetlands in the delta are (1) the Rio Hardy wetlands, which are <br />supported by the Rio Hardy River and high flow events in the Colorado River; (2) the <br />Cienaga de Santa Clara, sustained by agricultural runoff emanating from the Wellton- <br />Mohawk canal and the Riito drain; and (3) EI Doctor wetlands, which are supported by <br />artesian springs (Glenn et al. 1996) [Fig. 2]. In addition, riparian plant communities <br />dominated by Populus fremontii/Salix gooddingii{Tamarix chinensis have established in <br />several locations along the main channel of the Colorado River just north of the areas <br />influenced by tidal fluctuations of the Sea of Cortez. These wetlands ecosystems are <br />critical to a variety of wildlife. The Cienega de Santa Clara, for example, provides <br />habitat for the endangered desert pupfish (Cyprinodon macularis) and the Yuma <br />clapper rail (Ralus longirostris yumanensis) (Abarca et al. 1993). The delta's ecological <br />decline also appears to be intricately related to the decline of two other endangered <br />species: the totoaba fish (Cynosdon macdonaldl), which was once common throughout <br />much of the delta (Cisneros and Mata et al. 1995); and the vaquita porpoise (Phoceona <br />sinus), which is a harbor porpoise that is heavily dependent on the delta's protected <br />waters and nutrient supply (Mora lis and Abril 1994; Peggy Turk Boyer, pers. com., <br />1997). <br /> <br />Page 5 <br />