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DREDGING FOR DIPLOMACY?. THE BORDER ENVIRONMENT AT RISK McGeorge Law School February 19, 2005. presentation overview. the Colorado River limitrophe the dredging project environmental alternative. Less than 1% of the Colorado’s water reaches its delta.

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  2. presentation overview • the Colorado River limitrophe • the dredging project • environmental alternative

  3. Less than 1% of the Colorado’s water reaches its delta

  4. little native habitat remains on lower Colorado

  5. 15,500 acres

  6. Morelos Dam • final point of diversion • downstream flows erratic • siltation • overbank flooding

  7. flooding in limitrophe… native habitat created

  8. Soft-shelled turtle Side-blotched lizard Tree lizard Desert spiny lizard Whiptail bullsnake Cottontail Pygmy pocket gopher Desert pocket mouse Merriam’s kangaroo rat Deer mouse Muskrat Beaver Domestic dog raccoon limitrophe amphibians and mammals, 2003

  9. Abert’s towhee Verdin Ladder-backed woodpecker Cliff swallow Song sparrow Common yellowthroat Blue grosbeak Lesser goldfinch Hooded oriole Bullock’s oriole Ash-throated flycatcher Crissal thrasher Yellow-breasted chat Osprey Black chinned hummingbird Inca dove Bronzed cowbird Yellow-billed cuckoos Cinnamon teal Common moorhen Pied-billed grebe Green heron Yuma clapper rail Southwest willow flycatcher limitrophe birds, 2003high regional importance

  10. Southwest willow flycatcher • neotropical migrant • riparian obligate • prefers backwaters • endangered in US (300-500 breeding pairs)

  11. Yuma Clapper Rail • lives in marshes, wet riparian margins and backwaters • endangered in US (1500 individuals)

  12. public interest in limitrophe environment • Cocopah Tribe proposal in 2002 to create international protected area in limitrophe • Surveys in US and Mexico support protection of limitrophe ecosystem • Yuma birding festival • US-Mexico Minute 306 recognizes importance of limitrophe • BLM considering Area of Critical Environmental Concern status

  13. management for ecosystem • perennial flow • occasional overbank flooding • natural river meanders • conservation and restoration of cottonwood-willow forests • protection and creation of backwaters

  14. International Boundary and Water Commission • Relevant mandates include: • Minute 217 (1964) Relies on a 1940’s flow study Requires flood capacity of 140,000 cfs today considered the 10,000-year flood - Boundary Treaty (1970) Boundary determined by river channel

  15. IBWC PROJECT • Maintain flood capacity • Rectify US-Mexico boundary • Demarcate US-Mexico Boundary • Levee-to-levee capacity of 140,000 cfs • Pilot channel of 15,000 cfs

  16. IBWC PROJECT • dredge channel to establish and maintain bare-sand corridor, 300-750 feet wide • Severely degrade existing native habitat Environmental Defense response: • is project necessary? • can design avoid habitat destruction?

  17. Is the project necessary? • flood capacity of 140,000 cfs was established in 1940’s • Projects constructed since then include Flaming Gorge, Glen Canyon Dam, CAP, Morelos Dam and more • Phoenix, Las Vegas, San Diego have boomed • Today 140,000 cfs is the 10,000-year flood


  19. Can design avoid habitat destruction? • IBWC is planning 15,000 cfs pilot channel to increase levee-to-levee capacity AND to demarcate boundary • Existing levees deficient only in northern 4 miles of limitrophe

  20. integrated goals • protect life and property to level determined by cost-benefit analysis • address territorial concerns • enhance ecosystem values • contribute to local economy by increasing tourism value

  21. Preliminary Design Recommendations • Maximize use of levees to minimize need to destroy native habitat • Revisit need for 15,000 cfs pilot channel. Consult with fluvial geomorphologists to develop levee protection that eliminates or minimizes need for pilot channel.

  22. Avoid any modification of northern half of limitrophe where native riparian habitat values are high. • Make boundary adjustments as needed in the southern half of the limitrophe where native riparian habitat values are lower.

  23. Do not strand existing native riparian forest by diverting elsewhere the existing channel and the flows it conveys. • Incorporate restoration of cottonwood-willow trees, oxbows and backwaters, and other important riparian habitats into final alternative.

  24. Where things stand… • IBWC withdrew contract in summer 2004 • IBWC and CILA meeting to reassess flood control needs • Environmental Defense working on a design alternative to address “reasonable” flood control, boundary rectification, and habitat augmentation

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