Population Projections and Future Water Needs

image005


Flagstaff's Designation of Adequate Water Supply

Our Commitment to Water Security

The Adequate Water Supply Designation signifies that Flagstaff has demonstrated physical supply availability for 100 years, legal rights to water, water infrastructure, as well as financial and water treatment capabilities.

The designation provides:

  • A requirement for City staff to track new plats approved by City Council and associated water demands
  • Security for today's community and future residents
  • A demonstration to the state and our community that we are committed to the future
  • A focus on sustainable yield

Learn more about Flagstaff's Adequate Water Supply Designation.


Flagstaff's Future Water Demands

New demands = 7,700 to 16,500 acre-feet per year

Little soccer fields Thumbnail1 Acre-Foot = 325,851 gallons

1 Acre-Foot = Approximately 1 football field filled 1 foot deep with water.

This range was determined by:

  1. Assuming various density patterns for land uses in the voter-approved regional plan
  2. Population growth projections

Future Uncertainties

  • Warmer Temperatures
  • Snowpack Decrease
  • More Intense Storms
  • Growth Rate
  • Type and Density of Residential and Non-Residential Development

Scenario Planning

In scenario planning, we seek to find a robust solution(s) to address the broadest range of potential futures.

ScenarioPlanning flow chart that shows how future solutions are come from present concerns and branc

Climate Change Impacts on Supply and Demand

Of all the potential threats posed by climatic variability and change, those associated with water resources are arguably the most consequential for both society and the environment. Water - the Nation's Fundamental Climate Issue: A White Paper on the U.S. Geological Survey Role and Capabilities; U.S. Department of the Interior, U.S. Geological Survey; Circular 1347; 2010

Numerous studies and models are currently attempting to predict the impacts of climate change on water supply. In general, the Northern Arizona region can expect to experience the following effects:

  • Warmer temperatures, leading to increased evapotranspiration of surface water
  • More precipitation that falls as rain rather than snow
  • Decreased snowpack
  • Increased runoff, shifting earlier in the Spring

The U.S. Global Change Research (USGCRP) program conducts a National Climate Assessment (NCA) every four years. The USGCRP has stated that, "Climate change has already altered, and will continue to alter, the water cycle, affecting where, when, and how much water is available for all uses." In the most recent NCA report, published in May 2014, the USGCRP concluded that:

  • Water quality and water supply reliability are jeopardized by climate change in a variety of ways that affect ecosystems and livelihoods.
  • Short-term (seasonal or shorter) droughts are expected to intensify in most U.S. regions. Longer-term droughts are expected to intensify in large areas of the Southwest.
  • Climate Change is expected to affect water demand, groundwater withdrawals, and aquifer recharge, reducing groundwater availability in some areas.
  • Increasing air and water temperatures, more intense precipitation and runoff, and intensifying droughts can decrease river and lake water quality in many ways, including increases in sediment, nitrogen, and other pollutant loads.
  • Climate change affects water demand and the ways water is used within and across regions and economic sectors. The Southwest...[is] particularly vulnerable to changes in water supply and demand.
  • Changes in precipitation and runoff, combined with changes in consumption and withdrawal, have reduced surface and groundwater supplies in many areas. These trends are expected to continue, increasing the likelihood of water shortages for many uses.


Water Supply Monitoring

Monitoring allows us to track groundwater and surface water conditions over time

The Water Services Division supports two efforts that document conditions in the C-aquifer (the source of most of our water) and the Upper Lake Mary watershed. This monitoring data serves several purposes:

  • In areas where little development or pumping has occurred, data from these programs provides a way to determine baseline conditions. 
  • In all areas, monitoring data collected over time allows us to assess the degree to which pumping, drought, and other factors affect our water supplies. Knowing when impacts occur is key to protecting these supplies. 
  • Measurements of water levels and stream flow allow us to periodically recalibrate our groundwater model to real-life conditions. This helps ensure the accuracy of our model predictions, which we rely on for water resource planning and management decisions.

USGS C-Aquifer Monitoring Project

In 2010, the City began supporting this project. City dollars are matched by the USGS. The Navajo Nation also partners with the USGS on this project. Water levels are measured quarterly in 11 wells located in the Flagstaff, Red Gap Ranch, Clear Creek, and Chevelon Creek area (basically, between Flagstaff and Winslow); in addition, samples are collected from springs to track water quality.

Upper Lake Mary Watershed Monitoring Project

In 2014, the City Council authorized the Lake Mary / Walnut Canyon Technical Advisory Committee to support “flowtography” and the monitoring of surface water flows through Newman Canyon by the USGS. Partners include the Salt River Project, Northern Arizona University, the Flagstaff Watershed Protection Project, the Forest Service, and the National Park Service. Plans for 2017 include adding precipitation stations to monitor rain fall and snow fall.

Learn more about the ULM Watershed Monitoring Project

Other Monitoring Efforts 

The City also benefits from monitoring conducted by the Arizona Department of Water Resources (ADWR) at wells in the Red Gap Ranch, Skunk Canyon, and Woody Mountain areas and all across the region.


2012 Sustainability Study

The 2012 study focused on quantifying Flagstaff's current water supplies and conservatively project how they can meet our needs over the next 100 years. The study relied on a groundwater flow model to simulate aquifer conditions in and around Flagstaff by defining the regional subsurface geology and hydrology of the Coconino (C) and underlying Redwall-Muav (R) aquifers. The modeling efforts have not only helped us develop and implement sound water and management decisions, but they were instrumental in achieving Adequate Water Supply Designation.

Learn more about the 2012 Sustainability Study