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<br />, ~!:, . <br /> <br />a02739 <br /> <br />~ <br /> <br />Opportunities for Ecological Improvement Along the Lower Colorado River <br />Mark Briggs and Steve Cornelius <br />7/24/97 <br /> <br />amount of the brackish wetlands in the delta are almost completely sustained by <br />uunusable" agricultural runoff. A priority of future wetland conservation efforts <br />should be to develop strategies for using wastewaters more effectively. Indeed, at a <br />meeting between the heads of water management agencies of the U.S. and Mexico, <br />scientists, agricultural, municipal, and environmental representatives suggest that the <br />improved management of wastewaters could reestablish up to 40,500 hectares (100,000 <br />acres) of wetland habitat in the delta (Glenn et al. 1997). <br /> <br />Although the volume of municipal sewage effluent produced each year is much smaller <br />than that produced from agriculture runoff, it is likely to increase with expanding <br />urbanization. Depending on the quality of the effluent, some may also be suitable for <br />maintaining wetlands. Moreover, certain wetland areas could be developed <br />specifically to help clean municipal wastewaters, thus providing the dual benefit of <br />wetland habitat creation and contaminated water filtration. Of course, safe guards <br />would have to be developed so that wetlands do not become inexpensive disposal <br />zones for raw sewage. <br /> <br />Conclusion <br />Due to a variety of human-related impacts, much of the lower Colorado River native <br />wetland ecosystem is damaged or has disappeared completely. Only remnants remain <br />of the magnificent riparian cottonwood-willow forests that once graced significant <br />reaches of the lower Colorado River. In the delta, the majority of the remaining <br />marshlands are maintained via tenuous associations with agricultural runoff canals. As <br />ecological conditions along the lower Colorado River deteriorated, so to has the well- <br />being of the people and wildlife that depend on the river for their survival. During the <br />height of their dominion, the population of the Cocopah, the original river people, <br />exceeded 20,000. Today, scattered communities consisting of a few hundred <br />individuals remain, located for the most part on the backwaters of the Rio Hardy, and <br />near San Luis and Summerton, Arizona. Wildlife species such as the totoaba (a fish <br />species cherished by the Cocopah), the vaquita porpoise, desert pupfish, and the Yuma <br />clapper rail, all of which once thrived in the delta's ecosystem, are listed as <br />endangered. <br /> <br />From an ecological and conservation perspective, the situation along the lower <br />Colorado River has reached a critical juncture. To make significant progress in <br />repairing the ecological condition of the river, it is imperative to address difficult and <br />politically-charged bi-national policy issues such as groundwater drawdown, water <br />allocation, and dam releases. Of these, altering dam releases may provide the greatest <br />opportunity for broad ecological recovery of native wetland ecosystems. A significant <br />reason for the ecological decline of these ecosystems is river impoundment; <br />manipulating dam releases to mimic natural flow patterns would directly address this <br />problem and probably promote natural regeneration of native wetland plant species as <br />long as sufficient natural seed sources remain. <br /> <br />Page 27 <br />