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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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dredging for diplomacy



McGeorge Law School

February 19, 2005

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

Morelos Dam

    • final point of diversion
    • downstream flows erratic
    • siltation
    • overbank flooding

flooding in limitrophe…

native habitat created

limitrophe amphibians and mammals 2003
Soft-shelled turtle

Side-blotched lizard

Tree lizard

Desert spiny lizard




Pygmy pocket gopher

Desert pocket mouse

Merriam’s kangaroo rat

Deer mouse



Domestic dog


limitrophe amphibians and mammals, 2003
limitrophe birds 2003 high regional importance
Abert’s towhee


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


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

Southwest willow flycatcher

  • neotropical migrant
  • riparian obligate
  • prefers backwaters
  • endangered in US (300-500 breeding pairs)

Yuma Clapper Rail

  • lives in marshes, wet riparian margins and backwaters
  • endangered in US (1500 individuals)
public interest in limitrophe environment
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
management for ecosystem
management for ecosystem
  • perennial flow
  • occasional overbank flooding
  • natural river meanders
  • conservation and restoration of cottonwood-willow forests
  • protection and creation of backwaters
international boundary and water commission
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

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
ibwc project19
  • 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?
is the project necessary
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
can design avoid habitat destruction
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
integrated goals
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
preliminary design recommendations
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.
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.

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.

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