Apr 01 2019Share

Assured Water Supply Program: Protecting Homebuyers while Ensuring Responsible Growth

By Warren Tenney

For months we have heard about the looming shortage of Colorado River water and how Arizona must take action to reduce the risk of deeper shortfalls by approving the Lower Basin Drought Contingency Plan (DCP). At the same time, Maricopa County is the fastest growing county in the nation and already the fourth most populous county.

At first glance, these two contradictory details raise the question - will we have enough water? This is why it is important to understand a key fact about Arizona water management in the Phoenix and Tucson areas. Under the 1980 Groundwater Management Act, new subdivisions cannot be built unless they can prove they have access to a 100-year water supply.

The Act was passed to curb groundwater pumping in heavily urbanized and agriculturally dependent areas – known as Active Management Areas or AMAs – that were experiencing significant declines in groundwater levels. In AMAs, the Act prohibits the expansion of agriculture, regulates new wells, and requires conservation by all water users.Picture1

A cornerstone of the Act is the Assured Water Supply Program. It protects innocent homebuyers and ensures sustainable growth. No other state in the country can tout such a rigorous requirement.

The principle is simple: before building and selling subdivision lots within an AMA, the Arizona Department of Water Resources (ADWR) must determine that sufficient water of adequate quality will be available to satisfy the water needs of the subdivision for at least 100 years. These provisions protect a homeowner from turning on the tap, only to find that the supply has run out.

A typical developer does not own water rights and is not in the business of supplying water to your home. Instead, water is usually supplied by a city, town or private water company. Many of these "municipal water providers" choose to go through a rigorous application process with ADWR to prove that they have enough water to meet all of their current and future demands for 100 years. These entities are then "designated" by ADWR as having an assured water supply.

To receive a 100-year Assured Water Supply designation, a water provider must meet the following criteria:

  1. Physical Availability – Water must be physically available to serve the development for 100 years. Sophisticated scientific studies are used to evaluate how new growth will impact existing water users and regional water supplies. For groundwater, the proposed pumping must not cause existing wells to go dry, or the aquifer to decline lower than 1,000 feet below the ground surface. For surface water supplies, such as the Salt River Project (SRP), physical availability is determined by an analysis of how much water will be available each year when considering a variety of factors, including drought and climate change.
  2. Legal Availability - Once the water has been shown to physically exist, the development must receive commitment from a legally recognized service provider: often a city, town, or private water company.
  3. Continuous Availability – The water provider must prove that the water is continuously available, typically through the existence of water storage infrastructure, drought preparedness plans, and backup supplies.
  4. Water Quality – Water supplies are only as good as their ability to be used! That’s why water providers must show their water meets all State and Federal water quality standards.
  5. Financial Capability - The storage, treatment, and delivery of water is an intensive and expensive task. A water service provider must have adequate infrastructure in place, and the ability to finance maintenance, repairs, and replacement.
  6. Consistency with Management Plan - The water provider must meet the State’s water conservation requirements, which are meant to become increasingly rigorous.   
  7. Consistency with Management Goal - This is the key provision of the Assured Water Supply Program that ensures your water will not run out after 100 years. In the Phoenix, Tucson, and Prescott water management areas, the AMA goal is to reach safe-yield.  Safe-yield is the balance between the amount of groundwater withdrawn from an aquifer and the amount of water recharged to the aquifer through natural and manmade processes. Safe-yield is important because natural groundwater is finite, not a renewable supply. Once it is pumped, it is effectively gone. To show consistency with the goal of safe-yield, a water provider cannot rely on groundwater, but must use renewable supplies, such as SRP river water or Colorado River water from the Central Arizona Project (CAP).

Each AMWUA member is proudly designated as an Assured Water Supply provider. Like other designated water providers, the AMWUA cities must apply for re-designation every fifteen years, making the 100-year mark a rolling timeframe. The re-designation process ensures that the water sources you rely on will be evaluated regularly, with no surprises after 100 years.

The AMWUA members are committed to protecting the long-term sustainability promoted by the Assured Water Supply Program. We do not just plan ahead for next year’s water, but for the next century. It is this forward-thinking mindset that allows our municipalities to weather decade-long droughts and drives your community’s water managers to negotiate fiercely on your behalf to protect these water supplies.

The Assured Water Supply Program has encouraged the sustainable use of river water and recycled water, investments in infrastructure, and innovative ways of conserving and managing our water resources. It affords security for existing residents who rely on a clean dependable source of water and provides certainty for businesses who seek to invest in Arizona. As pressures increase on our State’s water, the Assured Water Supply Program forces Arizona to confront tough questions about growth and the willingness to develop responsibly, just as it was meant to.

Your support for this Arizona water law is crucial to maintaining a resilient economy that continues to grow viably even in a drier future.

For 50 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

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