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Water facts
Phoenix, Arizona:
Identifying and
Becoming More
Resilient to Impacts
of Climate Change
Cities across the United States should anticipate significant water-related vulnerabilities based on current
carbon emission trends because of climate change, ranging from water shortages to more intense storms
and floods to sea level rise. To help cities become more resilient to the rising threats of climate change,
NRDC reviewed more than 75 scientific studies and other reports to summarize the water-related
vulnerabilities in 12 cities—including Phoenix. Although there may still be some uncertainty about what
particular impacts threaten cities and how quickly or severely they might occur, action at the local level
is the most effective method of reducing, mitigating, and preventing the negative effects of water-related
climate change outlined in this fact sheet. NRDC urges cities to prepare for coming challenges relating
to water resources. Fortunately, there are steps cities are already taking to become more resilient.
Situated at the northeastern region of the Sonoran Desert,
Phoenix, Arizona has a subtropical arid climate with limited
yearly rainfall. Because of Phoenix’s limited water resources,
increased temperatures and decreased rainfall are very likely
to impact the availability of freshwater to homes, businesses,
farms, and institutions in Phoenix over the course of this
century.
Summary of water-related climate changes and impacts
in Phoenix throughout the 21st century
Water supply challenges due
to increased droughts
Decreased annual precipitation
Highly likely
Likely
Possible
Source: NRDC
For more
information,
please
contact:
Michelle Mehta
mmehta@nrdc.org
(310) 434 2300
switchboard.nrdc.org/
blogs/mmehta
www.nrdc.org/policy
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Precipitation and Droughts
Precipitation is projected to decline in southern Arizona by
5 to 10 percent by 2100. Although summer monsoons can
bring significant rainfall, high temperatures cause much of
that moisture to immediately evaporate. Winter snowfalls,
which are crucial to the management of the city’s water
supply, may be decreasing. These factors indicate increased
360,000
drought for the region.
340,000
Water Demand (AF)
Water Supply Challenges
320,000
Higher temperatures
and decreased precipitation are expected
to reduce water supplies.
300,000Based on the average of climate
scenarios, runoff into the Salt and Verde watersheds—from
280,000
where Phoenix gets much of its water supply—could decrease
260,000
by 23 percent. Water
imported from the Colorado River
system through the240,000
Central Arizona Project (CAP) helps
to alleviate the impact of droughts, but has been below
220,000
capacity due to drought
conditions and over-allocation.
During prolonged or severe drought conditions, the city
may not be able to count on water from CAP. Reduced
surface water supplies necessitate groundwater withdrawals
to meet demand, but overuse of groundwater can cause land
subsidence and reduced water quality. Another factor affecting
future water availability in Phoenix is population growth.
Expanding population could result in demand exceeding
supply by 2030, and higher temperatures combined with
drought conditions would increase annual household water
use even further because of increased evapotranspiration.
Action
Phoenix’s efforts to adapt to climate change are centered on
water resource management. Given its arid climate, the city
had already developed strategies to address potential deficit
conditions between water supply and demand before climate
change became a dominant factor. For instance, through
1,600,000
water demand management, the city
has been able to decrease
per capita water consumption despite
recent population
1,400,000
growth. Though current climate research has not yet yielded
1,200,000
data sufficient to be directly incorporated
into the decision
process, the city is planning for a variety
of future water
1,000,000
supply shortage scenarios. For instance, Phoenix currently
800,000
stores excess surface water supplies in underground aquifers
600,000
through the Granite Reef Underground
Storage Project; and
it uses more than 90 percent of the400,000
water treated by the city’s
three wastewater treatment facilities for crop irrigation, golf
200,000
course watering, habitat restoration,
and industrial cooling.
Population
Increased Temperature
Average temperatures are already on the rise in Phoenix.
According to the Southwest Climate Change Network, “The
Southwest is projected to warm faster than the world as a
whole in the coming decades, with summer temperatures
rising even faster than winter ones. Average annual
temperatures in many parts of the region could be 5 to 8
degrees F [2.8 to 4.4 C] higher than they were even during
the hot quarter-century that began in the 1970’s.”
200,000
9
19 8
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
0
20 7
08
20
09
20
10
97
96
95
94
93
92
91
90
0
19
19
19
19
19
19
19
19
19
City of Phoenix per-capita water consumption
280
Total GPCD (produced
including system losses)
Residential GPCD
(metered deliveries)
260
240
GPCD
220
200
180
160
140
120
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
94
19
93
19
92
19
91
19
19
90
100
Source: Adapted from City of Phoenix
Printed on recycled paper
© Natural Resources Defense Council July 2011
www.nrdc.org/policy