Long-range planning, investments in water supply alternatives, and a
history of successes in water conservation have allowed the city of Phoenix to
weather every drought to date without resorting to mandatory water use
restrictions or prohibitions. However, the city is prepared to establish such
restrictions in future years if absolutely necessary to ensure the safety and
health of our residents. Learn about Drought and Climate Change.
Though Phoenix has more than an adequate supply of water in non-shortage
years, residents and business owners are encouraged to review their water use,
and to plan for changes in how they use water to avoid more serious impacts
should drought become more severe.
Lake Mead, August 2003
Phoenix Water Services and Drought
In Arizona, the current drought is approaching 15 years in length (2000-2014) and has surpassed the worst drought in more than110 years of official recordkeeping. Beyond the written record, tree ring research reveals that 20 to 30 year droughts have occurred several times over the past 1,000 years in the major watersheds serving the city of Phoenix and surrounding municipalities.
During the current drought, Phoenix has been able to manage its available water supplies to meet the community's water demands. However, this record-setting drought is a warning. Given that we can't accurately predict when the drought will end, we all need to become more aware about the facts of drought and what the future possibilities and impacts from drought could be.
Though the City of Phoenix has adequate water supplies to meet all of the community's water needs even if the drought lingers for another ten to fifteen years, it is important to be aware of the steps that can be taken now to avert potential future impacts from severe, sustained drought. This website provides an overview of the facts about the current and possible future conditions of drought and what actions can be taken to reduce the impact of continuing drought.
Phoenix's Water Supply Portfolio
The city of Phoenix maintains access to several types
of water supply including: surface water, groundwater, and effluent or
“reclaimed” water. For normal years (in which our supplies are unaffected by
drought), more than 95 percent of customer drinking water demand is met with
surface water from two major sources. Salt River and Verde River water is
delivered through the Salt River Project (SRP) and Colorado River water is delivered via the Central Arizona Project (CAP) canal. The remaining volume (less than five percent) is groundwater pumped from city-owned wells. Reclaimed water is used as an irrigation supply for City parks and environmental restoration facilities.
Drought and Our Source Watersheds
The watersheds that supply surface water to Phoenix are much larger than the city or the metropolitan area as a whole. The Salt and Verde River watersheds encompass 13,000 square miles in the eastern and north central portions of Arizona, and the CAP watershed encompasses all or portions of seven states (Wyoming, Colorado, Utah, New Mexico, Nevada, California and Arizona).
NOAA National Drought Monitor Map (Click here or on map graphic at left to see current U.S. drought conditions)
These watersheds receive precipitation mainly in the form of snow in the mountains. When there is insufficient snow, runoff flows are low, soil moisture decreases, and drought conditions exist both on the watershed and in the desert valleys.
Reservoir storage on the river systems helps balance out naturally occurring fluctuations in snowfall and runoff from year to year, to better match availability of water with water demand. Long, continuous periods of reduced snowfall and scarce rains, however, have a cumulative effect on the reservoir storage and reduce the ability of the storage system to even out the good and bad precipitation years.
How is Phoenix Faring?
Fortunately, due to visionary water supply planning efforts for more than 100 years, Phoenix and surrounding municipalities have successfully managed available water supplies to meet growing demands with little if any impact on the economy and quality of life for the region. Abundant (though currently diminishing) storage in major reservoirs on the Colorado River and on the Salt and Verde Rivers and the ability to pump groundwater has allowed our region to continue to thrive despite the recent drought conditions.
Water demand (based on the overall use per capita) decreased by 25 percent in the 20-year period from 1994 through 2013. This can be attributed to a number of factors, including new homes built with low water use plumbing fixtures and appliances, new landscape restrictions requiring the use of desert adapted plants, and water conservation education programs.
Though drought has affected both the SRP and CAP systems, the Salt/Verde watershed is much more sensitive to drought given the smaller watershed size. This smaller size means that local weather conditions have a greater impact on water yield. On larger regional watersheds, like the Colorado River, localized weather phenomenon has less impact on the watershed as a whole.
Extremely low storage conditions in the Salt and Verde River reservoirs prompts SRP to reduce allocations to users. This has happened only four times since construction of Roosevelt Dam on the Salt River was completed in 1911. Fortunately, the City of Phoenix has access to some of the most senior rights in the SRP system, so the impacts of these reductions on Phoenix's water supplies have been minimal. To provide further water supply security, the City of Phoenix has invested in its own storage capacity on the Salt and Verde Rivers. As of July 1, 2014, the City held over 160,000 acre-feet of water in these facilities that can be used in the event of reductions in Phoenix's other supplies.
To date, allocation reductions have not been necessary on the Colorado
River/CAP system due to the more substantive storage capacity. However, as result
of the extended drought conditions in the region, the storage system on the
Colorado River is just over half full (as of July 1, 2014), and there is an
increasing probability that a Colorado River shortage could be declared as early
as 2017. The City’s CAP allocation would
not be impacted by such a shortage, but it would likely result in reductions in
the CAP water available to CAP agricultural customers. According to a June 26,
2014 statement by the CAP Board President, “CAP shortages are not expected to
impact Arizona cities for at least 10 to 15 years. That is because cities hold
the highest priority within the CAP system and so would be among the last to be
cut during shortage.” Fortunately, the
City of Phoenix, along with other local and State water resource managers, have
prepared well for possibility that a future shortage could impact our CAP
supplies. In 1996, the Arizona state
legislature created the Arizona Water Banking Authority, which has stored more
than two million acre-feet of water underground specifically for the purpose of
offsetting future CAP municipal shortages.
The City itself has stored more than 182,000 acre-feet of water (a
combination of its unused CAP supplies and reclaimed effluent) that can be
recovered in the event of a future shortage. In addition, the City is
implementing a program to increase our ability to pump groundwater from city
wells to help offset future reductions in surface water supplies.
Although Phoenix currently benefits from a diversified water supply portfolio, we are not immune from drought. It is possible that reductions in allocations of Colorado River Water to the State of Arizona or future more severe reductions in SRP allocations could result in the city of Phoenix incurring a supply shortage in meeting the community's normal water demands. While determining the precise timing and nature of these impacts is not possible, identification of the factors and uncertainties that bear on drought conditions is an important first step in preparing for these potential water supply shortfalls. Key uncertainties are:
The Growth Factor
Most new development utilizes low water use fixtures and landscaping. Thus, the average household water use of a new house is less than the average household water use of existing houses more than 10 years old. Commercial and industrial uses are also more efficient than past uses. The result is that in the city of Phoenix, the rate at which total water consumption is increasing is lower than our growth rate. To illustrate, the total water produced by Phoenix for its customers in 2013 was the lowest it's been since 1995, despite a 30% increase in population (340,000 people) during the same period of time.
Since the early 1990's, Phoenix has required new development to pay a water resources acquisition fee to help fund new water supply acquisition and development. This means growth forces are offsetting the cost of the acquisition and development of new water supplies. In a drought situation, such water supply development may prove critical. Thus, growth "pays its own way" in ensuring that it does not increase the city's vulnerability to drought.
In recent years there has been a great deal of community discussion about growth. The general consensus is that while the community does not like some of the negative effects of growth (such as congestion and declining air quality), it welcomes the economic benefits. We want those benefits to continue, but we want to manage growth to limit its negative effects. Phoenix's General Plan, as well as the General Plans for most cities in the region, is structured around this basic strategy.
The metropolitan Phoenix economy is fueled in large measure by regional growth. The city's strategy is growth management, not zero growth. Stopping growth would negatively impact the well-being of the City and the region. It would cause dislocations in employment throughout the region, and significantly dampen commercial activity, manufacturing, and service industries.
Through long-range water resource planning efforts, the city continually
strives to ensure that the demands of this growth can be met far into the
future. These efforts involve both management of our existing supplies and
acquisition of new supplies. As the drought deepens, this becomes especially
critical in protecting our local economy.
Shortage Sharing on the Colorado River
Under the current "Law of the River," the Colorado River's flow is divided by compact between upper basin and lower basin states. The lower basin states – California, Nevada and Arizona – share an entitlement of 7.5 million acre feet of water per year from the River. Additional water is released from Lake Mead to assure a minimum delivery of 1.5 million acre feet to Mexico in compliance with the U. S.-Mexican Treaty. Arizona is entitled to 2.8 million acre-feet of Colorado River water. However, about 1.7 million acre-feet of this allocation has junior standing on the system. What that means is that a shortage in the lower basin allocation dictates that Arizona is among the first to be cut back. California's (4.4 million acre-foot entitlement will be affected only after Arizona loses its entire 1.7 acre-feet of "junior" status water (more than half of the State's total allocation).
The CAP diverts about 1.5 million acre-feet of the state's Colorado River allocation into central and southern Arizona. If Arizona's allocation is cut back, the CAP supplies and other junior-status water uses along the Colorado River will be curtailed first. Within the CAP, annual Excess Water contracts will be cut back first, followed by Non-Indian Agricultural entitlements. Water available under the cities' contracts will not be curtailed until the CAP supplies are cut by at least one-third (or about 500,000 acre-feet).
City Water Distribution Infrastructure
The city of Phoenix water supply system has been designed specifically to provide water during shortage conditions. The water system design allows flexibility in how to respond as drought conditions change. The growth of our city and recent drought conditions have prompted a re-evaluation of the capabilities of this system under extreme shortages. The city's Water Resource Plan Update presents an evaluation of several potential future drought scenarios as well as numerous strategies for responding to drought. The city also is updating its Water System Master Plan. These plans call for additional water system features and water supplies to increase reliability during water supply shortfalls.
Long Term Objective
The basic strategy of the Phoenix Water Services Department is to ensure that adequate supplies are available to meet Phoenix's existing and new water demands, and to minimize the effects of drought on our economy and quality of life. Under normal conditions (including short-term dry periods), Phoenix has adequate sustainable water supplies to meet the State of Arizona's 100-Year Assured Water Supply standard. This includes growth in Phoenix's system water demand over the next 20 years or more.
It is possible, however, that during long, extreme drought conditions, Phoenix would have to institute mandatory water use reductions. It is the City's goal to notify our customers well in advance of such reductions and to minimize the impacts as much as possible.
Drought Response Strategy
Recognizing that long-term drought is possible, and that available water supplies could be reduced during a drought, the City of Phoenix has developed a long-term drought response strategy to better position the city to respond to changing conditions. It is only prudent for the city to plan responses for all drought stages should they become necessary in future years.
The city of Phoenix will accomplish this by doing the following:
Manage our water supply portfolio to meet the community's water needs today;
Increase efforts to plan for water needs under conditions of continuing drought;
Educate our customers about the situation now and possible future conditions, and;
Help our customers plan and implement conservation measures they can undertake now to soften the impacts of a more lengthy and severe drought.
While conservation is something all desert dwellers should engage in at all times, it is particularly important to managing water supplies during drought conditions. Preparing and planning for drought today will ensure the proper level of drought response in the coming years.
By being careful about how you use water you can help slow down the effect drought has on our water supply. There are a number of websites with information on water conservation.
Visit the water conservation sections on the City's website to learn about a variety of ways to conserve water.
Learn more about Drought and Climate Change
Also, the Water - Use It Wisely website lists more than one-hundred water saving tips for our area.