Marie Pearthree - Urban Water Institute, Inc.

Colorado River Basin
Water Supply & Demand
Study: An Arizona
Marie S. Pearthree, P.E.
Central Arizona Project
Assistant General Manager
Urban Water Institute
August 15, 2013
What is the Central Arizona Project?
336-mile aqueduct brings
Colorado River water from
Lake Havasu to Tucson
14 pumping plants lift water
nearly 3000 feet
11 underground pipelines
Lake Pleasant/New Waddell
Delivers 1.6 million acre-feet
of Colorado River water
Federal Reclamation Project
operated and maintained by
Single largest provider of
Colorado River water to
municipal and Native
American users in the Basin
Who Gets CAP Water (~1.6 MAF)?
Cities – For residential, commercial
and other customers
Tribes – For on-reservation use, off-
reservation storage, leases and other
purposes (46% of CAP Supply)
Farms – For irrigation of crops
Recharge Projects – For annual
and long-term storage
Why the Central Arizona Project is So Active
• CAP is the largest single Colorado River User within the
boundaries of the watershed.
• CAP has junior rights
• CAP delivers to 80% (5.3 million) of Arizona’s population
(approx. 1.6 MAF/yr)
• CAP is critical to preventing groundwater overdraft and
supports statewide recharge and replenishment
Preparing for Shortages & Imbalances
• Research Activities
‒ Climate Change
• Feasibility Studies
‒ Basin Study
• Water Consv.
‒ Desal, Ag, M&I
• Augmentation
‒ Weather Modification
‒ Desalination
• System Efficiency
‒ Brock Reservoir
‒ Minute 319 (Binational
‒ Vegetation Management
‒ Arizona Water Banking
‒ Recharge Projects
• Reduce Demands
‒ Continue conservation
Shortage Sharing: Impacts to CAP
Augmentation Needs
• 1975 Study finds “natural supply”
insufficient for growing demands unless
Basin States were willing “to accept the
limitation in water supply and pattern the
economic and social future of the basin to
that limitation.”
Same study determined the only option to
address future water needs is “to augment
the flows of the Colorado River thus
increasing its water supply and permitting
continued growth of water dependent
--Westside Study Report on Critical Water Problems Facing the
Eleven Western States (U.S. Dept. of the Interior, April 1975)
Augmentation Needs
• Post 1975, BOR identified several
augmentation options and proposals but
none initiated
• All seven Basin States renewed
investigation of augmentation and
feasible options, publishing a report in
--Study of Long-Term Augmentation Options for
the Water Supply of the Colorado River System
(Seven Basin States, March 2008)
• All four portfolios evaluated in 2012 Basin
Study included augmentation
Summary Basin Study – Options & Strategies
River imports
Wx Mod/Watershed Management
Non-tributary groundwater
Reduce Demands (Conservation)
Modify Operations
– M&I conservation
– Ag conservation
– Energy production conservation (drycooling)
– Evaporation reduction (covers)
– Reservoir management
– Water Banking
– Ag-Urban transfers
Water Importation Options
• Replace Colorado River
water to the Front Range
with Mississippi or Missouri
River water
• Potential to address water
issues at a regional and
national scale
• Long-term project but
with opposition
• Mississippi Annual
Discharge ~ 425 maf
• Colorado River Annual
Supply ~ 15 maf
Basin Study - Desalination Options
• Binational desalination
projects with Mexico
• Southern California Exchange
• Yuma Area Brackish Water –
Operating the Yuma Desalting
Plant or alternatives
• Salton Sea Brackish Water Irrigation Drainage Water
Sonora Desal Concept
NOT An Alternative!
Basin Study-Conservation and Reuse Options
• No specific programs identified in
the study
– Central Arizona (AMAs)and Las
Vegas lead the nation in
municipal and industrial water
– Arizona leads the nation in
irrigation efficiency
– CAP and Arizona stakeholders
continuing investments
• Need to identify new programs
and how to fund them
– water conservation is not “free”
Basin Study-A Call to Action:
• Significant imbalances by 2060
• Potential for critical imbalances begin as early as 2025.
• Imbalances are driven by climate change/prolonged
droughts plus increasing demands.
• Augmentation projects, increased conservation, and
reuse can resolve the “average” imbalances –
protecting the Colorado River and its users.
• Implementation of large-scale projects and programs
will take a more than a decade.
• Efforts to develop augmentation, conservation and
reuse programs and projects must begin now.
Basin Study: Multi-faceted Call To Action
• By implementing additional
measures, projected future
imbalances in supply and
demand can be
successfully managed
• Multi-faceted approach
• Federal government must
partner with states
Marie S. Pearthree, P.E.
[email protected]

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