A positive step in the face of uncertainty

Enormous uncertainty best describes the condition of Phoenix’s climate and water supply in the 21st century. Reservoirs have dipped to their lowest levels, and continuous drought has plagued the state. Forecasts for even warmer summers are predicted. Despite this uncertainty, ASU professors say there is no need to be fearful because positive impacts can be made.

Patricia Gober and Craig Kirkwood, working in conjunction with Decision Center for a Desert City (DCDC), which specializes in decision-making under uncertainty, assessed the climate’s affect on water shortage in Phoenix. Their results were published in the Dec. 14 issue of the Online Early Edition of the Proceedings of the National Academy of Sciences. A special section in this PNAS issue focuses on what the 21st century climate in the Southwest will mean in terms of sustainability.

Their paper, “Vulnerability assessment of climate-induced water shortage in Phoenix,” discusses simulation modeling and the principles of decision-making under uncertainty. It looks at human vulnerability to environmental risks in terms of water shortages, in addition to examining factors that affect water supply, while providing numerous options for solutions.

Factors such as population growth, increased development, outdoor landscaping and a larger number of private pools all affect water supply. Gober and Kirkwood used an integrated simulation model called WaterSim to investigate the long-term consequences of policies that manage groundwater, growth and urban development in Phoenix.

Gober, who also is director of DCDC, said the goal is not to preach an agenda but to provide the science that supports better decision-making.

“If you make this set of choices, then you can continue to have a vibrant city even under dire climate conditions. We have a smorgasbord of choices,” Gober said. “You pick the menu items that are going to work best for your community.”

Adapting to a shortage in water supply, Gober said is “not a one-size-fits-all answer.” The paper points out a few things people can do, such as changing their type of landscape, limiting the number of pools in a community, building a higher density city, and investing money to fix water leaks.

Gober, who also studies the relationship between energy and water in relation to the urban heat island, said: “Just because we don’t know what’s going to happen with the climate, doesn’t mean we can’t or shouldn’t do anything.”

Funded by the National Science Foundation, water supply research at DCDC explores risk management and solution strategies. "Uncertainty can paralyze decision-making," Gober said. "But DCDC and this paper say, 'Look, we don’t know what the future holds, but we can still do things to reduce risk and protect ourselves from water shortages.'"