The Central Arizona Project (CAP) and Planning for Times of

Shortage

Sharon B. Megdal, Ph.D. Director, Water Resources Research Center, The

University of ArizonaElected Member, Board of Directors, CAP

Hermosillo, MX May 7, 2010

The WRRC MissionThe 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 MapCAP Serves Three Central Arizona Counties

Source: Central Arizona Project5

El Río ColoradoAportaciones

Cuenca Baja – 9,250 Mm3 (7.5 maf)

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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)

Cuenca Alta - 9,250 Mm3 (7.5 maf)

México - 1,850 Mm3 (1.5 maf)

Cuenca del Río Colorado

Arizona (Cuenca Alta)

62 Mm3 (0.05 maf)

Source: Central Arizona Project6

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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 LevelsInformation below as of April 25, 2010

Source: U.S. Bureau of Reclamation12

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Shortage Sharing Guidelines

• Stage 1 shortages are mathematically possible as soon as 2012, but not very likely; the USBR 24-month 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. 15

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• 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

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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