WSP12542

• File Number: 8282.400
• Description: Colorado River Operations and Accounting - Deliveries to Mexico
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 5/1/2001
• Author: David and Lucille Packard Foundation
• Title: Immediate Options for Augmenting Water Flows to the Colorado River Delta in Mexico - RE-Colorado River-Mexican Delta Issues - 05-01-01
• Water Supply Pro - Doc Type: Report/Study

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II. OVERVIEW OF THE COLORADO RIVER DELTA

For purposes of this report, the "Delta" is defined as the area including: approximately 100
miles of the Colorado River corridor in Mexico upstream of its confluence with the Rio Hardy; the
Rio Hardy drainage; the Cienaga de Santa Clara; the Laguna Salada; and the river's inter-tidal zone
and tidal flats leading to the Gulf of California. Figure 1 is a Landsat photo of the irrigated and
Delta area in Mexico.3

The value of the historic Delta for ecological purposes cannot be overstated. Even today,
the ecological resources of the Delta are impressive. Because the Delta supports more than 160,000
shorebirds, 60,000 waterfowl, and a dozen threatened or endangered species of animals, fish, and
plants, the Delta was registered in 1996 as a Ramsar site. The Ramsar Convention recognizes
wetlands that meet criteria for international importance. The Delta also has been part of the
Western Shorebird Reserve Network since 1992. The Delta's survival is important for many
purposes beyond just ecological conservation. Since earliest times, it sustained fisheries on which
indigenous peoples depended And for many years, the Delta was a destination for hunting and
fishing, making it economically important for tourism.

Realistically, the Delta cannot be restoted to the conditions before the Colorado River
waters were harnessed in the 19305. It is realistic, however, to expect that a sustainable supply of
water allocated to the Delta could maintain the quality of habitat restored during the 19805 and
1990s, when the Delta benefited from larger than normal Colorado River flows. There currently
exists an opportunity to develop a common vision of what is meant by "restoring the Delta."
lbrough the Minute 306 process and through dialog among interested parties and organizations, it is
hoped that the geographic scope and detail of scientific study, minimal ecosystem management
requirements, restoration objectives and operational strategies can be agreed upon.

TIlls report seeks to identify immediately available sources of water that could be used for
this purpose. It also proposes to improve the existing habitat through better management of the
water. These measures are neither intended to nor do they answer the overall Delta water problems.
Once an overall Delta management program is identified, the interim water supplies and
management strategies identified herein could be withdrawn, depending upon the overall needs and
commitments of the parties.

A. Changes in River Flows

Historically, the Colorado River was an active river that continually changed channels in the Delta as
its large loads of sediments were deposited, creating natural berms and dikes. The energy and extent
of its nutrient-carrying floods created extensive floodplains with rich and abundant wetlands. The
wetlands served as a nursery for fish, a home for numerous mammals, and as habitat for both
resident, and migratory birds using the Pacific Flyway. Where the river reaches the Gulf of
California, it historically combined forces with a large tidal zone, resulting in one of the most
productive and diverse estuarine ecosystems in the world, supporting both wildlife and indigenous
communitie~ dependent upon fishing for their subsistence life style. Moreover, until the 1970s, the
Delta was a key destination for US and Mexican hunters due to its large bird population.

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