The Central Arizona Project (CAP)
and Planning for Times of
Shortage
Sharon B. Megdal, Ph.D.
Director, Water Resources Research Center, The
University of Arizona
Elected Member, Board of Directors, CAP
Hermosillo, MX May 7, 2010
The WRRC Mission
The University of Arizona's Water Resources
Research Center (WRRC) promotes understanding of
critical state and regional water management and
policy issues through research, community outreach
and public education.
The WRRC is committed to:
 assisting communities in water management and policy;
 educating teachers, students and the public about water; and
 encouraging scientific research on state water issues.
Web site: www.cals.arizona.edu/azwater
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Arizona Water Management
• Surface water and
groundwater managed
separately by the state
• Colorado River water
managed differently
than other surface water
• Groundwater
Management practiced
in Active Management
Areas (shaded areas on
the map) according to
the Groundwater
Management Act
• Federal Role is limited,
especially with respect
to groundwater
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El Proyecto de Centro-Arizona
• El Proyecto CAP
– Construcción
terminado en 1993
Proyecto de Centro-Arizona
• COSTO - $3.6 billion de dolares
• CAPACIDAD - >1,900 Mm3
• LONGITUD – 540 kilometros
• AUMENTO DE ALTURA – 730
metros
• SIRVE 4 millones de personas
y 100,000 hectáreas de
agricultura
Source: Central Arizona Project4
CAP System Map
CAP Serves Three Central Arizona Counties
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Source: Central Arizona Project
El Río Colorado
Cuenca del Río Colorado
Aportaciones
Cuenca Alta - 9,250 Mm3 (7.5 maf)
Cuenca Baja – 9,250
(7.5 maf)
************
California – 5,425 Mm3 (4.4 maf)
Arizona – 3,455 Mm3 (2.8 maf)
(CAP –>1,900 Mm3 (1.5 maf))
Nevada – 370 Mm3 (0.3 maf)
Mm3
México - 1,850 Mm3 (1.5 maf)
Arizona (Cuenca Alta)
62 Mm3 (0.05 maf)
Source: Central Arizona Project
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Colorado River was Allocated based on a wet period
in history: Colorado River at Lees Ferry Gaging
Station, Arizona , Water Year 1906 to 2009
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Colorado River Drought
• 2000-2009 has been the driest 10-year period in the
100-year historical record (WY 2008 and WY 2009
data are estimated)
• Tree-ring reconstructions show more severe
droughts have occurred over the past 1200 years
(e.g., drought in the mid 1100s)
• Forecasted 2010 April through July runoff is 66% of
average as of April 15
• Not unusual to have a few years of above average
inflow during longer-term droughts (e.g., the 1950s)
Source: U.S. Bureau of Reclamation9
Lake Mead: The storage reservoir for the
Lower Colorado River Basin
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Low Flows due to drought and climate
change a key concern to CAP due to its
Junior Priority
• The CAP low priority means that CAP is
particularly vulnerable to shortages. Its
allocation will be reduced to zero before
California experiences shortage.
• In order to alleviate the harsh impacts of this
junior status, Arizona worked with the other
seven basin states to develop shortage sharing
guidelines, which were adopted by the U.S.
Secretary of the Interior in 2007
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Shortage Sharing Guidelines were
developed that consider Lake Mead and
Lake Powell Storage Levels
Information below as of April 25, 2010
Source: U.S. Bureau of Reclamation
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Shortage Sharing Guidelines
• Stage 1 shortages are mathematically possible as
soon as 2012, but not very likely; the USBR 24month study does not show a shortage occurring
in 2012
• No shortage that would impact CAP Cities and
Indians is expected before mid-2020s
• Guidelines assist AZ planning efforts
• According to CAP staff, negotiations are
underway with Mexico to determine the nature
of any shortage sharing between Mexico and U.S.
water users.
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What is CAP doing to prepare for Climate
Change?
• Planning for potential shortages, other impacts
• Participating in the modeling of river runoff
scenarios
• Evaluating alternative options – Adaptive
management, river augmentation, conservation
(Yuma Desalting Plant and Drop 2 Reservoir)
• Storing excess water underground today for use
during shortages
• Arizona Water Banking Authority has built up significant storage
in Central Arizona to use during times of shortage to CAP M&I
customers.
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CAP Water Storage Facilities
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What is being done to improve the
Colorado River watershed climate models?
• Participating in regional and national research to
improve the accuracy of climate models;
downscaling global models to improve their
utility for the Colorado River basin
• Developing new methods to use climate models
to generate stream runoff projections for use in
Colorado River system models
• Using tree-ring data to develop a stream flow
record for the past 1,240 years to capture a wider
range of runoff variability
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How much does evaporation affect CAP
and will that be impacted by climate
change?
• Current evaporation rate is less than 5% of
CAP deliveries (less than losses in municipal
delivery systems which are about 10%)
• Even a 20% increase in temperature due to
climate change would result in < 6% total
evaporation
• Recharge site evaporation is less than three
percent
• Recovery planning is important
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Is the glass half full or half empty?
There are many issues to be worked on
and many people working on them!
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Issues and Challenges
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Drought, Climate Change
Growth and the need for additional supplies
Water and Energy
Water management outside the Active Management Areas
(AMAs), including water quantity assessments
Water Quality
Use of effluent for potable and other water needs – the next
major new water source
Access to and utilization of renewable supplies
Transboundary water issues
The surface water/groundwater interface
Riparian areas and other environmental considerations
related to water
Conservation Programs
Recovery of Stored Water
Approaches to replenishment
Water cost/pricing
Water Planning
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Gracias!
¿Preguntas?
smegdal@cals.arizona.edu
Thanks to staff at the Central Arizona Project for
information and graphics contained in this presentation.
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