Water Resources

Upper Lake Mary Spillway
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Objective 6: Ensure Adequate Water Resources and Plan for Climate Change

Relevant Standards

  • Maintain 100-year Adequate Water Supply Designation as administered by the AZ Department of Water Resources
  • Ensure that the risk of a sustained water delivery shortage is extremely low
  • Continue to build resiliency in water supplies and infrastructure systems with specific attention to the forecasted effects of climate change
  • Maintain a diverse and redundant water-supply portfolio, including optimizing the use of reclaimed water
  • Encourage efficient water use while maintaining quality of life
  • Conduct water loss assessments, per AWWA standard


Flagstaff’s water supply currently comes from three sources, Upper Lake Mary, pumping water from deep aquifers (approximately 1000-2,000 feet below the ground), and reclaimed water. Upper Lake Mary has always been a highly variable supply, its yield determined by yearly snowpack and precipitation. The deep well aquifers have provided a reliable source of high-quality water. Flagstaff residents and businesses have cut water use per-capita by over 50% since 1989.


  • Climate change models indicate accelerating uncertainty about yearly snowpack and precipitation, potentially decreasing the availability of Upper Lake Mary as a water resource and impacting aquifer levels.
  • Loss of Upper Lake Mary would increase costs due to pumping of additional groundwater and trigger the search for a new water resource.
  • Although Flagstaff currently maintains its 100-year Adequate Water Supply Designation, the City pumps more groundwater in certain well fields than is naturally replenished by snowpack and rain.
  • Future natural replenishment could decrease significantly with climate change.
  • Increased temperatures and “longer summers” will increase overall water demand.
  • Water resources planning and engineering codes must consider future conservation efforts, including the effects of “demand hardening” on supply reliability and the impacts on wastewater collection and treatment.

Timing Concerns

Climate change is accelerating, resulting in increased uncertainty in water supply issues, indicating more aggressive planning and communications should begin now.

Specific Responses

  Champion Action Items Timing
1.    Update planning with respect to Flagstaff’s water  resource and climate change impacts, including updating  the risks associated with current water resources and the  100-year supply designation (Water Resources Master  Plan). Water Resources Manager This will take a bit of time to achieve. First step is to work with Water Resource Technician to make a general water balance model.
2.    Update predictions on the ongoing yield of Upper Lake  Mary based on climate change considerations Increase  monitoring and management of aquifer water levels  through strategic operations and better understanding of  recharge rates and its locations. Water Resources Manager Received a report from CLIMAS staff.  
3.    Continue promoting water-use efficiency, as per the  adopted 2020 Water Conservation Strategic Plan Increase   the use of reclaimed water, including recharge to   augment groundwater supplies and evaluating other  options, such as Direct Potable Reuse.   Completing a draft of the WCSP for council. Submitted the Leadership Board application to Alliance for Water Efficiency. Working with Brown and Caldwell on reclaimed water master plan and step of forming a community steering committee on reuse in flagstaff.  
4.    Develop measures that establish a sustainable water  budget, or safe yield of groundwater by 2033 (the 20-year  period established by ADWR in the Adequate Water  Supply Designation).   This will take a bit of time to achieve. First step is to work with Water Resource Technician to make a general water balance model.  
5.    Work to foster a continued community conservation ethic  to ensure future supply reliability (considering the  impacts of demand hardening on reliability, the wastewater treatment system, and reclaimed water).   Water Conservation programming continues - developing measures with the Water Conservation Implementation Plan  
6.    Enhance communications on climate change and water  resources, including clearing up confusion related to the difference between infrastructure and water resource                 limitations.   Will work on developing our stance, education, and proposed policy related to climate change.  

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