Water & Climate Change

Upper Lake Mary Spillway
2011_Shallow_Well_drilling2 obj 1

Objective 6: Ensure Adequate Water Resources & 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.


Water Services Strategic Plan 2025

Objective 6: Ensure Adequate Water Resources and Plan for Climate ChangeReporting Period:   January-June 2020Reporting Period:            July-December 2020
 Specific ResponsesChampion & TEAMAccomplishmentsAccomplishments Next Steps
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
Consultant provided a scope to assiste WRM with planning. John R. and EMY have had several meetings in 2021.Create a water balance model
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
Reviewing report from CLIMAS staff. 

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
Working on implementation plan for WCSP. Submitted the Leadership Board application to Alliance for Water Efficiency. Water Production produced over 1 billion gallons surface water, higher than any year since 2011 and only achieved 20 times in Flagstaff's history; reducing demand on all groundwater aquifers.Working with Brown and Caldwell on reclaimed water master plan and step of forming a community steering committee on reuse in flagstaff.
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)

Working with John R., to frame water resources story. Work on creating a general water balance model
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

Maximize the use of GIS to organize data with respect to geographic location
Have made progress on a water demand model, with EHS.

Enhance communications on climate change and water resources, including clearing up confusion related to the difference between infrastructure and water resource limitations
Working with consultant on this topic.
Developing education and policy related to climate change