Peak Demand Dictates How Cities Build Water Infrastructure

By Warren Tenney

It’s no surprise that demand for water in the Phoenix Metro area reaches its peak during the summer months. What may be surprising is that demand nearly doubles from the winter months to the summer months. In February 2015, City of Peoria customers – businesses, apartment buildings and homes – used 2,940 acre-feet of water. In July, Peoria’s peak rose to 6,516 acre-feet of water. (One acre-foot of water is enough to cover an acre to the depth of one foot or enough to serve an average of three Arizona households for a year.) In December 2015, City of Mesa water customers used 5,899 acre-feet of water. In July 2015, Mesa water customers used 10,503 acre-feet.

The annual pattern of peak demand can look slightly different from year to year, depending on fluctuations in heat and when monsoon storms arrive. The chart below shows Mesa’s annual water production for the past 5 years. Peaking in Mesa happens most often in July, but a hot June and a good July monsoon can mean that the peak month could be June.Screen Shot 2016-08-17 at 8.10.27 AM

Watching water-use trends and peak demand is critical to planning and building water infrastructure. Here’s why:

  •  Annual Peak Demand: Cities build infrastructure to meet annual peak demand. It would be cheaper to order just enough water and build just enough pipes, pumps and small reservoirs within a water system to meet average water use but that would make water delivery to your faucets unreliable during peak demand times. More is invested in water treatment and distribution systems to ensure they are built to provide water for the hottest days when landscape irrigation systems, pools and cooling towers are working at maximum capacity.
  • Daily Peak Demand: Each day, demand for water peaks in the morning and, again, in the evening hours. That means water managers are diligently filling a water system’s reservoirs overnight to make sure enough water is ready to be pumped to homes when hundreds of thousands of residents step into their showers between 6 a.m. and 7 a.m. Then water managers dial back around 9 a.m. when demand lessens and to prepare for the after work demand.


    Small reservoirs keep water available for peak demand. Photo: City of Mesa

  • Safety Peak Demand: Being ready for daily and seasonal water demands isn’t enough. Water managers must maintain water supplies and build water systems for the what-ifs. What if it’s 6 a.m. on a July morning and firefighters call for more water to fight two house fires and a brush fire? What if the system is just dialing back to accommodate a low demand time when a water main breaks spewing hundreds of thousands of gallons of water meant for customers into the street instead? A water distribution system must have supplies, pipes, reservoirs and pumps in reserve to keep water running to customer faucets while employees fix the break or provide water for fire suppression.

Most cities, including Mesa and Peoria, use a computer program called Supervisory Control and Data Acquisition or SCADA to track water demand throughout their systems. The program allows city employees to keep their eyes on each part of the water distribution system remotely and in real time. Operators use this innovative computer program to review water distribution continually throughout their service area and to track peaks in demands. For example, a sudden change in pressure could mean firefighters need high volume and increased pressure to put out a fire, a construction site is filling a large water tank, a reservoir is overflowing or there is a break in the system and the city is losing water.  Utility workers can quickly respond to investigate and correct the problem to significantly reduce any disruption to your water service. 

Mesa Canal Connection

Photo: City of Mesa

During the last two decades, while Mesa and Peoria have grown by hundreds of thousands of people, the water used by city customers, even during peak demand months, has remained nearly flat. Cities helped to fuel this accomplishment by promoting a conservation culture, which includes encouraging drought-tolerant landscapes and the use of water-efficient appliances and fixtures, and helping residents find and fix leaks. Want to help lower your city’s peak demand? Start outside where as much as 70 percent of a home’s water is used. AMWUA’s Smart Home Water Guide can help you find and fix leaks. AMWUA’s landscape pages can help you select drought-tolerant plants and trees, design a lovely yard, and efficiently water your landscape for maximum beauty.

For 47 years, Arizona Municipal Water Users Association has worked to protect our member cities’ ability to provide assured, safe and sustainable water supplies to their communities. For more water information visit

Water: A Conversation with Scottsdale’s Mayor Lane

By Warren Tenney

Jim Lane’s resume is packed with past and present memberships on important governing boards, such as the League of Arizona Cities and Towns and Maricopa Association of Governments. After becoming the City of Scottsdale’s Mayor in 2009 he added one more, Arizona Municipal Water Users Association’s Board of Directors. Since then, he has been a regular at the monthly meetings, has served as AMWUA’s Board president and is now the Board’s secretary/treasurer. He is AMWUA’s longest serving Board member. During his 43 years living and working in Scottsdale, the Mayor has taken an interest in the Valley’s efforts to secure water supplies, in particular from the Colorado River, and the progress cities and the state have made saving and cleaning once-polluted aquifers. His active role as Scottsdale’s mayor comes first, but the Mayor said AMWUA is second. “Water is foremost in my mind, “ he said. “A resource so vital to our ability to grow and to be productive.” We thought it was time to sit down and talk water with the Mayor.

Q. What’s with all these golf courses in Scottsdale? It’s a desert city after all. 

A. “Golf is an industry. It is one of our primary industries. We have come to recognize it as one of our primary exports. People come here, buy an experience, and take it home. In order to accommodate that, we were the first – and maybe the only – city in the state to have 23 of those golf courses on a separate recycled water system. It’s a separate system the golf courses paid for themselves to water their golf courses. So, it waters their turf and keeps them in water at a competitive rate. It’s highly treated, but it’s reclaimed water.”

“Nearly a quarter of our general fund dollars comes from tourism, not to mention the fact that people who have second homes here are paying property taxes. It pays for basic services, police, fire, streets, roads, and libraries. Our direct tourism dollars – this would be bed-tax funds – enable us to off-load from our citizens the cost of maintaining TCP (Tournament Players Club), WestWorld, to build the Museum of the West and those kinds of things that end up enhancing our tourism traffic.”

Q. What question about water do people ask you the most?

Mayor Lane HeadshotA. “What is a little, sometimes, bothersome is that now I’m getting questions like: We have a water crisis. What are you doing about it?  I don’t ever want anyone to think we’re in la-la land, and in denial of challenges ahead of us. And so I try to say, look, we are as ready for this as anybody is. And we’re working every day on fine tuning and planning, not only solutions but conservation and growth. Another thing I share with them: In five years of increasing population our (City of Scottsdale’s) water consumption is flat.”

Q. Are you worried about climate change and what it could mean to our water supplies?

A. “No. I guess I’ve got to say I’m still a skeptic. I’m always concerned when the government is trying to assume more and more control over something, either to control or to tax. I concern myself with the motivation. Have we had cycles in our weather? When I was a younger man, the new ice age was coming. Then it changed to global warming. Then when things weren’t going that way, then we’re talking about climate change. I think we do have climate change, and I think we’ve always had climate change. But, nevertheless, I guess I’m a bit of a skeptic. I know some consider me a knucklehead because of my thinking and my skepticism on this subject.  Whatever the case may be, we still have to respond and manage our water according to the conditions before us.”

Q. Your city has worked hard to encourage residents to use water efficiently and provide innovative incentives to help residents conserve, such as rebates to remove water softeners and pools. Do you see cities as partners with environmentalists?

A. “The contrast we have with the environmentalists  – and I’d say maybe with the purest of the environmentalist’s side – is that we’re still advocates of growth. It has to be managed. I don’t mean managed in the sense of growth. I mean we have to manage our resources to make sure we can sustain our economy and our growth. That doesn’t mean by abusing our resources, it means by conserving our resources and making it work. But we’re not going to tell everybody to leave. We don’t see humans as the problems. We see them as something we have to accommodate and grow with.”

Q. So you’ve been in your home for 29 years. Have you made any changes to make it more water efficient?

A. “When the kids were home, we had a small soccer field out there (the back yard) so we went (with grass) from wall to wall. When they were all gone we decided to rein it in a little bit. We like the grass but it works out fine for us as it is right now, probably sometime we’ll change that configuration again. All the edges are Xeriscape. The front yard and most around the pool is all Xeriscape and has been from the beginning. When I built this house we hired a guy from ASU. He was a specialist in Xeriscape so all our vegetation was adapted. We weren’t into a lot of non-indigenous plants. We have over-seeded (the grass) in the winter a couple of times. When our oldest son got married we reseeded and we had the wedding here. And there have been a couple of times since then that I’ve done that, but it’s not a matter of course. It looks great but it’s just not worth it.”

Q. What are the water issues we haven’t talked about that you think are important?

A. “One thing is a concerted effort to get rid of salt cedar (also known as Tamarisk) in our watershed areas and primarily the Colorado River basin – 30 gallons (of water each tree uses) a day for millions of trees. It’s not indigenous to the area. It’s not right for our area. That’s a huge problem. I know it’s been a futile effort up until this time. Totally inadequately funded and I think that’s a major problem. It’s an outrage.”

Prescribed burn in Coconino National Forest Photo: SRP

“The second is forest management, which directly affects the water we receive in the Valley. I’ve spent the last several years trying to partner with environmentalists and you realize that we are looking for the same thing, ultimately. There will be differences in how we get there. But forest management is one of those critical things in which environmentalism – in the purest form – has really worked against us. It’s created the wildfire scenario where high-intensity flames just burn things to dust and destroy the watershed and pollute with biomass materials coming down in the drainage. This creates a monumental addition to (water) processing costs, which is a further carbon footprint as far as the power used to reprocess this (polluted water).  And then there is, frankly, the pollution of the water to boot and the inadequacy of soil conservation and, therefore, a denigration of the watershed and its development. Those are huge areas. The Four Forest fund initiative we actually contributed to at my suggestion. The City of Scottsdale will contribute $120,000 over the next three years to that fund as a participant. And my constituency would ask me: why are we contributing to that? Frankly, it’s our watershed.”

Q. How has AMWUA changed in the seven years you have helped to lead it?

A. “When I first came onto AMWUA it was a very different organization. It was just sort of a much lower profile organization doing the basics of representing the municipalities with SRP (Salt River Project) and CAP (Central Arizona Project). Now we’ve become more of a policy advisor for a wider group of folks, or I’d like to think we are. The credibility and reputation we’re building is a positive thing.”

For 47 years, Arizona Municipal Water Users Association has worked to protect our member cities’ ability to provide assured, safe and sustainable water supplies to their communities. For more water information visit

Monsoon Season: 5 Common Landscape Mistakes

By Warren Tenney

In writing about the monsoon season, I’m hoping we do not jinx having more storms. The monsoon season in the Valley is a great time of year for suddenly cooler temperatures and extraordinary sunsets, but it makes caring for desert landscapes a bit more mysterious. There’s more weather than usual: humidity, dust, rain and high winds. With lots of anticipation for more monsoon activity, we asked conservation specialists from a few AMWUA cities about the five most common landscaping mistakes during the monsoon season. Here’s what they told us.

1. Watering too often. Some people are so concerned with rising temperatures they make the mistake of watering plants every day. Watering too frequently can keep the soil too moist and lead to rot, fungus and other diseases. Plants thrive on monsoon humidity.  They do better when you water less frequently but with deeper soakings, about 2 feet deep for shrubs and three feet for trees. (You can measure by sinking a pointed wooden stake into the ground.) Watering deeply and less frequently creates an underground reservoir of water for plants and trees that will not easily evaporate and will encourage healthy roots. Large desert trees do best with very little water during the summer. This discourages heavy top growth and soft wet soil, which makes it easier for them to uproot and fall over in high winds. When you do water trees, water out to the edge of the tree’s canopy. This gives trees a longer, deeper and stronger root system to steady them in a storm. Landscape Watering by the Numbers offers you more precise information.

2. Wasting rainwater. If it has rained about a half inch in your neighborhood, you can turn off your watering system. That saves you money on your water bill and saves water for all of us. Better yet, you also can contour your yard to help your plants and trees get the most out of each storm. Sunken gardens and deep wells around your trees help to slow, to spread and to sink rainwater instead of allowing it to run off your property.  It’s the simplest rain harvesting technique and takes nothing more than a shovel, a little energy and thoughtful placement of plants. Consider this: 1 inch of rain on a 1,000 square-foot roof produces 600 gallons of runoff. The Valley receives an average of 7 inches of rain a year. It makes sense to plant at the roofline and to build swales to direct runoff toward trees and plants.

ma_tree down

 Photo: City of Mesa

3. Leaving trees without proper support. Swaying in the wind can help young trees grow stronger. The wind also can uproot them if they are not staked properly. To properly stake a tree use two stakes 6 inches from the trunk and gently attach them to the trunk with looped ties that allow the tree to sway in the wind. Allowing the tree to move with the wind creates a dense wood and strong trunk that will help keep mature trees standing despite the weather. Properly pruning helps established trees stand up to monsoon winds. Here are four pruning tips to help keep an established tree standing and avoid losing limbs during storms: 1) do not cut off lower limbs, 2) do not top a tree (shear off the top), 3) do not cut it into an umbrella shape, and 4) do not aggressively thin a tree leaving excessive foliage on the end of branches.

4. Applying herbicides during rainy weather. Rain is rarely gentle during the monsoon. Hard and fast rain rushes across your yard carrying any herbicides you’ve applied into the streets. From there it flows into storm drains or catch basins, which are usually located along street curbs, and into storm drain pipes deep underground. Most of this untreated runoff empties directly into riverbeds, washes and retention basins in city parks. Herbicides only add to the pollution the runoff carries with it. You can learn more about the importance of storm water at Stormwater Outreach for Regional Municipalities (STORM). Hand pulling weeds out of moist soil after a storm is easier and best for the environment.

Broken Spray Head

Photo: City of Mesa

5. Abandoning an irrigation system. No one can blame you for getting out of town for most of the summer and never experiencing the monsoon. (Perhaps you’d just prefer to stay indoors and abandon the yard work for a few months.) Here’s the problem: many homeowners trust their yard to an automated irrigation controller. Electrical storms can get your irrigation timer off schedule or even set your controller back to a default schedule (and sometimes cause irreparable damage). While the controller may be reliable, your pipes, sprinkler heads and drip lines are less so. Drip lines are particularly susceptible to weather. High temperatures, dust, and rain can clog, crack and break emitters and lines so each time that reliable controller comes on plants don’t get watered or gallons of wasted water pools in your yard. Pooling water gives mosquitoes a place to breed, wastes your money and everyone’s water. Check sprinkler heads for mower damage. Grass and leaves also can clog sprinkler heads. If you leave for part or most of the summer, make sure a neighbor, friend, family member, or a gardener regularly walks your yard while the irrigation system is running and is prepared to spot and stop any leaks. AMWUA’s Smart Home Water Guide can help.

Enjoy the monsoon season along with your plants and trees and keep this in mind: the monsoon season means Fall weather is getting closer.

For 46 years, Arizona Municipal Water Users Association has worked to protect our member cities’ ability to provide assured, safe and sustainable water supplies to their communities. For more water information visit


Water Bank Recovery: Preparing for Shortages on the Colorado River

By Warren Tenney

For many years, the State of Arizona has been storing water underground to prepare for times of drought. One way Arizona has accomplished this is through the efforts of a little-known state agency called the Arizona Water Banking Authority, commonly known as the Water Bank. Since its establishment in 1996, the Water Bank has stored Arizona’s unused Colorado River water underground, rather like a savings account. This savings account acts as a buffer if shortages cut water supplies from the Central Arizona Project (CAP). The CAP is a 336-mile canal that transports Colorado River water across the state to central Arizona and the Valley.  If necessary, the Water Bank will use this stored water to replace certain water supplies needed by cities, industrial users, and tribes when drought and shortage hits the Colorado River.

Central Arizona Project canal  Photo: CAP

The creation and operation of the Water Bank is one of Arizona’s water success stories.  Arizona has done an excellent job storing water underground.  Since its establishment 20 years ago, the Water Bank has stored 3.4 million acre-feet of CAP water. One acre-foot is enough water to supply 3 average Arizona households for one year. This water is in addition to the water Arizona cities have stored underground for decades within city limits or in regional underground storage facilities.

The next challenge is to complete the plan for the eventual pumping or “recovery” of the Water Bank’s water. How this water is recovered is one of the most important issues facing municipal water providers in the Phoenix area.

It is important to know that the Water Bank’s primary responsibility to date has been to store water. The agency is not equipped to transport, recover or distribute water. Arizona law states the Water Bank and CAP are to work together on recovering stored water. CAP has significant infrastructure in place and the ability to develop more, so CAP’s involvement is critical to ensure the eventual recovery of this water.

Understanding the importance of defining how recovery would occur, the Arizona Department of Water Resources (ADWR), CAP, and the Water Bank in 2014 jointly developed basic principles about how to recover stored water during a shortage. While the respective agencies have made progress in planning for recovery, additional work is needed so municipalities have greater certainty as to how recovery of this stored water will occur and meet their needs.

AMWUA recently identified and analyzed the outstanding issues that need to be resolved to provide a complete recovery plan and give the cities greater certainty.  Here is a brief summary:

Tonopah Recharge 28

Tonopah Desert Recharge Project Photo: CAP by Philip A. Fortnam

  • Distribution of Water Credits: Every acre-foot of water stored by the Water Bank creates a credit so the Arizona Department of Water Resources can track the amount of water stored. It is not clear how these credits would be distributed during a shortage and in what amounts.
  • Roles of CAP and the Water Bank: Arizona laws state that the Water Bank and CAP are to work together on recovering saved water, but it doesn’t provide specifics on their individual roles. Over the past several years, the Water Bank and CAP have worked on an agreement to clarify their roles, but that agreement is not yet final.
  • Infrastructure and Costs: Pumping and delivering the water would require expensive infrastructure, such as wells, treatment facilities, and possibly the use of canals. Existing infrastructure could be used, but many water experts anticipate that additional infrastructure would be necessary.
  • Water Quality: There are some unknowns about the quality of recovered water based on where the Water Bank has stored it. Testing and possible treatment of water may be required.
  • Water Exchanges: Another question is whether cities and the Water Bank could engage in exchanges of water that would decrease the costs of recovering water. For example, some experts have suggested that the Water Bank could store water underground in Tucson now for the City to use during shortages. When shortages come, Valley cities could then receive Tucson’s allocation of CAP water at their existing canal-side water treatment plants. This is similar to the current agreement Phoenix has with Tucson and Metro Water District.    

This is a simplified summary of a complex issue. The importance of this issue, however, is clear: While the first shortage cut won’t affect the cities, cities still want to be as well prepared as possible with their water supplies for when a shortage may impact them.  The Water Bank and CAP working to clarify outstanding questions regarding recovery of stored water will give municipalities greater certainty.  This is one more way in which Arizona continues to plan and be ready for whatever water challenge it must face.

For 47 years, Arizona Municipal Water Users Association has worked to protect our member cities’ ability to provide assured, safe and sustainable water supplies to their communities. For more water information visit

Water Bank: Arizona’s Emergency Savings Account

By Warren Tenney

In the early 1990s, Arizona was not using all the water it was legally due from the Colorado River. Instead, much of Arizona’s unused water flowed down the Colorado River to California. Here’s why: Under the law that governs the Colorado River, the Secretary of the U.S. Department of Interior can give water not used by one state to other states. As a result, each year California was the beneficiary of at least some of Arizona’s unused water. At the time, there were also concerns that Nevada would soon eye Arizona’s unused allotment.

Arizona’s Colorado River water is used in multiple ways. One major use is to irrigate agricultural lands along the Colorado River, most prominently in the Yuma region. In addition to on-River farming, more than half of Arizona’s allotment goes to municipal, tribal and agricultural users in Central Arizona. These users receive the water through a 336-mile canal that transports water across the state called the Central Arizona Project (CAP).  Since most municipal, tribal and agricultural users did not use their full allotments of water in the 1990s, their unused Colorado River water went to California. This was an unsettling predicament for a desert state that expected a surge in population.  Arizona’s mantra became “leave no water on the River.”

To address concerns that Arizona’s water was going to California, water managers AWBA Logodeveloped a concept to deliver unused water through the Central Arizona Project to store underground. This stored water would act as a buffer for times of drought. With support from the Arizona Department of Water Resources, AMWUA, and others in the water community, the Arizona Legislature in 1996 established the Arizona Water Banking Authority, more commonly called the Water Bank. Today, the Water Bank has stored 3.4 million acre-feet of water for Arizona. (One acre-foot of water serves an average of three Arizona households for a year.)

Here are the two ways the Water Bank stores water:

1. Underground Storage Facilities: With help from CAP, the Water Bank delivers Colorado River water to one of many underground storage facilities in central and southern Arizona. CAP, cities and other water agencies operate these storage facilities. These water storage sites consist of large constructed ponds called recharge basins. These basins are designed to allow the water to easily percolate into the ground. The water enters the natural aquifer where it is available to be pumped up through wells and delivered to customers affected by a shortage of Colorado River water.

Southern Avra Valley Storage and Recovery Project. Courtesy of Tucson Water.

Southern Avra Valley Storage and Recovery Project. Photo: Tucson Water

2. Groundwater Savings Facilities: These facilities work as a water exchange. In this case, Colorado River water is delivered to participating agricultural lands and used to irrigate crops. Participating farms or irrigation districts that receive river water agree not to pump an equal amount of water from the aquifer, thereby “saving” water underground. In the event of a Colorado River shortage, the water that was saved in the aquifer would be pumped or “recovered” and delivered to customers, such as cities, to help make up for shortages.

In recent years, CAP has had less unused or “excess” water. This is because municipal, tribal and agricultural users have been using more and more of their CAP water allocations.  As a result the Water Bank has less unused water to store from the “excess pool.”  When there was more excess water, the Water Bank stored an average of 250,000 acre-feet of water a year. In the last two years, that number has dropped to an average of 65,000 acre-feet.

There is currently a 56 percent chance the Secretary of the U.S. Department of Interior will declare a shortage of Colorado River water as early as 2018. Under the law that governs the Colorado River, the Secretary declares shortages based on the water levels in Lake Mead, the giant reservoir that sits behind Hoover Dam on the Colorado River at the Arizona-Nevada border. A 16-year drought has driven Lake Mead to its lowest level since the dam was completed in 1936. A possible 2018 shortage declaration would not affect the water supplies for cities, but would impact agricultural users and the Colorado River “excess pool” from which the Water Bank draws its water.  

The Water Bank has allowed Arizona to take all of its water off of the River and store it for a “dry” day.  The 3.4 million acre-feet of water stored by the Water Bank is a key component of Arizona’s preparations for eventual shortage.  As part of these efforts, it is important that the Water Bank, CAP, and water users develop a comprehensive plan for how the stored water can be recovered to help cities if a shortage declaration impacts their water supplies. 

The creation and operation of the Arizona Water Banking Authority is just one more example of how Arizona has led the way in water investment and innovation. This legacy continues to drive the water community as we tackle the challenge of looming shortages on the Colorado River.

For 46 years, Arizona Municipal Water Users Association has worked to protect our member cities’ ability to provide assured, safe and sustainable water supplies to their communities. For more water information visit

Safe-yield: A Balancing Act For Arizona’s Aquifers

By Warren Tenney

The goal of safe-yield has motivated Arizona’s cities to maximize their use of renewable water supplies – such as river water or recycled wastewater – and to minimize pumping groundwater. Safe-yield means the amount of water pumped out of the ground is the same as what goes back into underground aquifers. The efforts of Arizona’s cities to use renewable supplies and to protect groundwater have helped the Phoenix metropolitan area to weather a 16-year drought.  It is also why we are able to sustain long-term economic strength and enjoy our desert lifestyle.  Arizona’s innovative groundwater law—known as the Groundwater Management Act of 1980—designated safe-yield as a goal for the Phoenix Metro area. 

Groundwater is rain and snowmelt that has settled over thousands of years between rocks and gravel beneath the surface of the Earth.  Groundwater that settles in aquifers is a finite source of water.  Before 1980, uncontrolled pumping was depleting central Arizona’s groundwater, resulting in a lower water table, fissures in the ground, and cracked building foundations.  The Groundwater Management Act required farmers and cities to stop the unsustainable pumping of groundwater and encouraged them to use more water from the Colorado, Salt and Verde Rivers. Today only about 7 to 10 percent of the water used by AMWUA cities is made up of groundwater.

To help meet the safe-yield goal of the Phoenix area, cities financed the construction of treatment plants and other infrastructure necessary to use river water and recycled wastewater. Cities also have invested in storing water underground to meet and sustain safe-yield.

How To Recharge An Aquifer

Storing water underground is known as “recharging” the aquifer. Cities recharge water for at least two purposes: (1) to build up a bank account of water underground for times of drought, and (2) to offset groundwater that a city pumps and delivers to businesses and citizens. There are several ways to recharge or store water in an aquifer. Here are a few.

  • Recharge Wells: Cities build two main types of wells to recharge water into an aquifer. The first is a well dug 150 to 200 feet into the ground to direct water back into the aquifer. These are called “vadose zone wells” because they are sunk through the vadose zone or the upper part of the aquifer. The second type of well is called an “aquifer storage and recovery well” or ASR. This is a deeper well that goes 600 to 1,000 feet into the middle of the aquifer. These wells allow cities to both pump water directly back into the aquifer and pull it back out when needed.


    A vadose zone well in Scottsdale.

  • Recharge Basins: Some cities create basins filled with recycled wastewater or river water. The basins are built to help the water easily percolate back into the ground. These are known as recharge basins. Recharge basins come in a variety of sizes, from large regional facilities that allow multiple entities to store water at one location, to smaller recharge basins often owned by individual cities. Some cities create recharge basins on the site of their treatment plants, while others turn portions of them into recreational areas. For example, the Town of Gilbert turned some of its recharge basins into a 110-acre wildlife habitat called the Riparian Preserve at Water Ranch, located near Guadalupe and Greenfield roads.
  • Managed Recharge: Some cities receive permits to discharge river water into normally dry streambeds, where the water filters back into the aquifer.

    "Aerial shots of GRUSP"

    Granite Reef Underground Storage Project is a regional storage facility. PHOTO: Salt River Project

How Cities Make It Happen

Like many Valley cities, the City of Scottsdale recharges water into its aquifers as part of its commitment to contribute to the region’s goal of safe-yield. The City recharges most of this water within the city limits through vadose and ASR wells, and it also recharges water at regional recharge basins owned by Salt River Project and the Central Arizona Project.

Along with water from the Salt and Verde Rivers delivered by SRP, Scottsdale receives water from the Colorado River through the Central Arizona Project (CAP). Each October, Scottsdale Water places an order for its annual allotment of 80,000 acre-feet of Colorado River water with Central Arizona Project. One acre-foot of water serves an average of three Arizona families for a year.  Scottsdale’s current demand for Colorado River water is about 60,000 acre-feet per year. This leaves 20,000 acre-feet available to store.

Scottsdale sends the remaining 20,000 acre-feet of Colorado River water to one of two regional recharge facilities in Maricopa County. These recharge facilities provide two advantages. First, the facilities allow the city to return the water to the aquifer, which allows Scottsdale to do its part towards the safe-yield goal for the Phoenix metro area. Second, it allows the city to store or bank additional water it doesn’t need immediately for future use.  

The state’s water agency, Arizona Department of Water Resources, tracks the amount of water each city pumps out and recharges back into the ground. The agency does this to monitor if a city is contributing to the regional goal of safe-yield. The Department also tracks the amount of water each city returns to the aquifer as storage and gives the city a “long-term storage credit” for each acre-foot it stores, minus a 5 percent donation to the aquifer. This will allow cities to withdraw the correct amount of water when it is needed. 

What It Means To You

In 1980, wells in Maricopa, Pinal and Pima counties pumped out 2.3 million acre-feet more groundwater than could be recharged naturally. In 2013, the groundwater overdraft in Maricopa, Pinal and Pima counties had been reduced to about 382,000 acre-feet due to the Groundwater Management Act, including efforts to reach safe-yield.

The Groundwater Management Act only applies to the state’s five most populated areas called Active Management Areas. In recent years, the Phoenix Active Management Area has met its safe-yield goal.  The challenge is to continue to sustain safe-yield and ensure we have water to meet our future demand.  AMWUA cities will continue to seek and promote solutions to ensure that central Arizona achieves safe-yield to protect our most valuable resource—water.

For 46 years, Arizona Municipal Water Users Association has worked to protect our member cities’ ability to provide assured, safe and sustainable water supplies to their communities. For more water information visit



















Salt River: Bringing Life To A Desert Valley

By Warren Tenney

A likely shortage of Colorado River water in Arizona is big news. It should be. Colorado River water makes up 44 percent of the state’s water supply delivered through 336-miles of canals and pumps known as the Central Arizona Project. Colorado River water is important to Arizona but it is not the state’s only source of drinking water.

Salt River Project (SRP) operates eight dams, seven reservoirs and 131 miles of canals that bring water from the Salt and Verde rivers to the Phoenix metropolitan area. SRP provides 12 percent of Arizona’s water and is the largest provider of water to the Phoenix Metropolitan area.

A Short History

The Salt River has served the Valley since the ancient Hohokam people settled here in the year 300 A.D. These Native Americans built a 500-mile canal system that brought river water into their villages and fields for the next 1,000 years. They vanished around 1450.

The Hohokam had been gone nearly 400 years when an 1860s gold rush attracted fortune seekers to the Salt River Valley. Among them was Jack Swilling, an ex-Confederate cavalryman, who saw an opportunity to use water from the Salt River via canals to grow crops. He sold those crops to miners and the U.S. Calvary stationed at Fort McDowell.

Individuals, private companies, and associations started digging dozens of ditches trying to replicate Swilling’s success. The luckiest of these ventures lasted 30 years. Then came the same natural phenomenon that historians suspect pushed the Hohokam from the Valley: drought. The Salt River could no longer provide enough water for all the canals and thousands of acres of crops withered. Like the Hohokam, hundreds of pioneers left the desert village. 


To thrive, Phoenix needed a dam that would collect and store river water in the mountains to the north and east. The 1902 National Reclamation Act provided Phoenix with federal loans to build two dams on the Salt River, Theodore Roosevelt and Granite Reef Diversion. The federal government also bought out the ditch companies and connected all the canals into one system.

Ranchers and farmers who had remained in the Salt River Valley organized the Salt River Water Users’ Association and pledged their lands as collateral for the federal loans. In 1917, the federal government turned over the operation of the canal system to the Salt River Valley Water Users’ Association, which continues to operate the canals for the federal government as the Salt River Project.

Roosevelt Dam provides both a reservoir and hydropower. The Roosevelt Dam began supplying hydroelectric power to a copper mine in 1912. To increase its power capacity, SRP built three more dams along the Salt River before 1930. By 1946, SRP had built two dams on the Verde River. (These dams do not generate hydropower.)

After World War II the Salt River Valley was rapidly turning into an urban center that needed water for residential customers, rather than solely ranchers and farmers. In 1952, the City of Phoenix established the first contract with SRP to divert water from its canals to treat and deliver to homes. By 1984, SRP was delivering 55 percent of its water to Valley cities.

How It Works

The Salt and Verde rivers flow into Roosevelt Lake behind Roosevelt Dam. The reservoir can hold 1.6 million acre-feet or enough to meet SRP contracts for two years.

Canyon Lake

Canyon Lake

  • The water then runs through three reservoirs that are popular recreation lakes for Valley residents: Apache, Canyon and Saguaro. The Verde River water flows through Horseshoe and Bartlett lakes.
  • The water is released back into the Salt and Verde rivers, which eventually converge behind the Granite Reef Diversion Dam east of Mesa.
  • From there the river water enters into the Valley’s familiar canal system via gravity and is distributed to city water treatment plants and to farms.

SRP serves water to a 375-square-mile area and electricity to more than 1 million customers. The total SRP system today is about 55 percent full – just about the same as one year ago. In this 16th year of drought, the January-to-May snowmelt into the Salt and Verde rivers was below the median flow for the sixth consecutive year. The bright spot? The Phoenix metropolitan area has reduced its demand for water over the last 20 years.

What It Means To You

The Salt River and the Colorado River provide the AMWUA cities with a robust water supply. SRP makes up 53 percent of the water portfolio for the 10 largest cities in Maricopa County.  Having more than one source of water means a stronger economy for the Valley and a more reliable source of water for you.

SRP is unique to Arizona. We are all stewards of the Salt and Verde rivers. The watershed and forests that created and nurture these water sources must be managed well. We all have a responsibility to protect our watershed and forests, whether through making certain our actions do not cause a fire when camping or getting involved in forest restoration efforts. The health of our forests impacts the quality and sustainability of our water. 

Want to learn more about Salt River Project? Here’s a great place to begin.

For 46 years, Arizona Municipal Water Users Association has worked to protect our member cities’ ability to provide assured, safe and sustainable water supplies to their communities. For more water information visit