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000579 IN DEPTH WATER Colorado River Delta Efforts Make Progress Michael Cohen, Senior Research Associate Recent flood releases from upstream dams have prompted the resurgence ofthe delta's riparian habitat. Mention of the Colorado River evokes images of powerful rapids racing through deep canyons, of the untamed and the primeval. Yet the reality of today's Colorado river is far more mundane: it is a river controlled by dams and depleted by diversions, managed for off stream use and hydropower generation. One of the areas most affected by the taming of the Colorado River is the river's delta-estuary ecosystem. Historically, the Colorado River delta and the Upper Gulf of California sustained tre- mendous levels of biological productivity and diversity. As late as 1922, after much of the delta had been cleared for agriculture and irrigators had begun to divert the river, Aldo Leopold described the region as a "milk and honey wilderness." Human demands have dramatically reduced the amount of water reaching the delta. Except for unusually high flood years, virtually the entire flow of the Colorado is now captured and used before reaching the river's mouth. However, even without the historic flows the remain- . ' ing delta and upper gulf ecoregions still comprise the ~~largestand mostcriticaldesert-welfand in North America , as well as one of the world's most diverse and productive marine eGosystems. ~~- In recent years, flood release flows from upstream dams have prompted the reemergence of native cotton- woods and willows - creating more native riparian habitat than in the rest of the lower Colorado River - and have been strongly correlatedwith-a-rise in the shrimp catch in the Upper Gulf, an indication of the renewed viability of an important estuary. Sensible Strategies Can Lead to Recovery Although the original conditions in the delta probably cannot be restored, several plausible strategies for delivering water to the delta could improve and maintain a substantial area of critical habitat and recreate the estuary conditions necessary for the recovery of endan- gered species. More efficient management and allocation of the region's waters would not only improve ecosystem health, but could simultaneously provide substantial socioeconomic benefits for the indigenous tribes and fish- ing communities in Mexico that historically have relied on the river's water for their livelihood. Until recently, the ecological and social significance of the delta/upper Gulf region were almost entirely ignored. Users and regula- tory agencies disregarded environmental impacts in general, and paid no heed to the impacts of management decisions on habitat and communities in Mexico. This was partly due to the limited number of stake- holders - primarily U.s. irrigators and urban water districts - empowered to participate in decision-mak- mg processes. Yet in the past year, in re- sponse to the efforts of the Pacific Institute, other non- governmental organizations (NGOs), and academic re- searchers in the U.S. and Mexico, recognition of the eco- logical value of the delta and Upper Gulf has grown markedly, even as a host of adopted and proposed changes pose new threats to the delta. One of the most significant recent threats was created by the adoption of Interim Surplus Criteria (ISC) in January of this year. The ISC, designed to provide additional Colorado River water to California to facili- tate the implementation of plans to reduce California's dependence on such water, will reduce the frequency and magnitude of the space-building and flood release flows that currently sustain the delta and enhance the Upper Gulf estuary. To mitigate these potential impacts, the Pacific Insti- tute and the NGO community proposed an alternative Continued on next page