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Water Supply and Demand Model

The Challenge

Central Arizona is facing a water crisis, but not one of water shortage. Because the past century of leadership planned its water supplies to meet growing demands, Central Arizona has enough water to meet current and near-future needs.

In the 21st century, Arizona faces new challenges, including long-term drought, climate change impacts and austere public finances. These challenges require new approaches to water sustainability that focus on choices, priorities and smart investments.

The fundamental issue is how we will choose to use our available water to sustain our economy, quality of life and natural environment

Access WaterSim Phoenix

The Tool

Arizona State University created the WaterSim model to estimate water supply and demand for the Phoenix Metropolitan Area. Users can explore how water sustainability is influenced by various scenarios of regional growth, drought, climate change impacts and water management policies.

WaterSim is a systems dynamics model. It is a “systems” model because it takes a lot of data that is usually collected separately – including water supply, water demand, climate, population and policy data – and puts it together to give the user a system-level view of how these variables interact. It is “dynamic” because users can change one variable and see how that change affects the other variables.

WaterSim is a visualization tool. Rather than poring over pages upon pages of charts and tables, users can view the data in graphic form. They can make side-by-side comparisons to understand how one variable relates to another. Launched in 2007, WaterSim is now in its fifth iteration, and can be viewed online, through a web API, or in person at ASU’s Decision Theater.

Water Sim tool Graphic

The Variables

WaterSim allows users to change variables one-by-one, and then see how each change affects the water sustainability of the region and its various communities. By understanding best- and worst-case climate scenarios and the influence of various policy options on water supply and demand, decision makers can make choices informed by the best science available.

Water Supply – How much water is available, and where does it come from? The Phoenix Metropolitan Area receives its water from many sources including river water, groundwater and water reuse. Water supply is primarily influenced by climate.

Water Demand – Which communities use the most water per person? How much will those communities grow? Does that community have agriculture? How efficiently is water used? Water demand is primarily influenced by policy and population growth.

Climate Change – We cannot predict exactly how climate will affect water supply and demand in the future. What we can do is look at past patterns – decades with high flows, low flows or high variability from year to year – to understand best- and worst-case scenarios.

Population Growth – The population of Great Phoenix has been steadily growing for decades. Will it continue to grow at this pace, or will it grow faster or slower than predicted? WaterSim users can create best- and worst-case scenarios by changing this variable.

Policy Decisions – Who gets to use the water that is available? Individuals, businesses, farmers and ecosystems all require water, and some water must be stored for future use, as well. WaterSim users can manipulate allocation of water for these various uses.




WaterSim America

Expanding the modeling effort of WaterSim, DCDC’s WaterSim America model is a unique hands-on, state-of-the-art immersive visualization tool used to explore the complexity of water supply and demand. WaterSim America explores water issues on a state level and has been implemented as a proof-of-concept exhibit within Smithsonian Institution’s Water/Ways exhibition. This nationwide exhibition will travel to 25 states and 180 rural communities from 2016-2020. Water/Ways will tour Arizona from June 2018-April 2020.

Water/Ways Tour Schedule:

  • May 2016-April 2017: Florida, Illinois, Minnesota, Idaho, and Wyoming
  • May 2017-April 2018: Virginia, Alabama, Tennessee, Kansas, and Guam
  • May 2018-April 2019: Louisiana, Michigan, Mississippi, Nebraska, and Arizona
  • May 2019-April 2020: Oklahoma, Arizona, New Jersey, Maryland, and Texas
  • May 2020-April 2021: South Carolina, Missouri, California, Utah, and North Carolina

The interactive, educational game challenges visitors to develop custom sustainability solutions to specific water management issues in their own state. Learning from professionally-produced videos, engaging graphics, and an intuitive and simple-to-use interface, exhibition visitors select from a variety of realistic solutions to balance water supplies and demands. Sustainability indicators help users to understand the trade-offs they face between water conservation, agriculture, economic development, and environmental preservation.

Developed by researchers at Arizona State University, the model uses the following data sources for water sustainability indicators.

  1. Groundwater
    • Total Groundwater Withdrawal as a % of Safe Yield Estimates
    • GRACE, JPL; Global Land Data Assimilation System, NASA; National Snow and Ice Data Center, University of Colorado Boulder
  2. Surface Water
    • Withdrawal by Water Treatment Plants as a % of Stream Flows
    • Water Use, Surface Water, USGS; Water Treatment Plant Data, EPA
  3. Economy
      National Water Economy Project Logo FEWsion logo
    • Data for this indicator was provided to us by Dr. Benjamin Ruddell at Northern Arizona University, in association with the NSF-funded NWEP and FEWSION projects.
    • Local Water Used for Goods Production as a % of Total Water Use
    • Freight Analysis Framework, FHWA USDOT; Water Use, USGS; Employment Population, US Census; Agricultural Acreage, NASS USDA
  4. Environment
    • Wastewater Discharge as a % of Total Stream Flow
    • Surface Water, USGS; Wastewater Treatment Plants, EPA
  5. Agriculture Efficiency
    • Gallons Per Dollar of Agriculture Production Per Day
    • Water Use and Power, USGS; Net Farm Income, NASS USDA
  6. Urban/Rural Efficiency
    • Gallons Per Capita Per Day
    • Water Use and Population, USGS
  7. Power Efficiency
    • Gallons Per Megawatt of Power Produced Per Day
    • Water Use and Power Production, USGS