TUCSON, Ariz.— The proposed Interstate 11 through Arizona would spur dramatic population growth and an unsustainable increase in water demand, according to a new report.

Deadpool Highway, released today by the Center for Biological Diversity, uses government population and water-use estimates to analyze seven growth areas — future development officials say justifies building the 280-mile north-south highway through the desert.

“This proposed interstate is based on growth for which there isn’t enough water,” said Russ McSpadden, Southwest conservation advocate at the Center for Biological Diversity and co-author of the report. “The highway would spawn unsustainable suburban sprawl and worsen water scarcity in the midst of a megadrought with no end in sight. Interstate 11 should be shelved before any more tax dollars are wasted.”

Among the report’s findings:

• Population in growth areas would soar more than 10 times from roughly 220,500 people to more than 2.8 million, increasing Arizona’s population by a third.
• Water use would increase more than 10-fold, from 33,593 acre-feet of water per year to 396,400 acre-feet per year. That’s 2,774,800 acre-feet every seven years, roughly Arizona’s entire annual Colorado River allotment.
• At least one area, metropolitan Phoenix’s West Valley, lacks enough water to support the development Interstate 11 is proposing to serve.
• The highway’s environmental analysis doesn’t consider how much water demand it could induce or whether there’s enough water to support these growth areas.

Climate change-driven warming and drying, and the overallocation of Colorado River water, have left Lake Powell and Lake Mead perilously low. In 2023 Arizona entered a Tier 2 shortage and the federal government cut its Colorado River supply by 21%.

Groundwater is also overallocated in the state, with cities, farms, developers and other entities claiming the right to use more water than exists. As a result, wells and water supplies for agriculture and desert cities are drying up as groundwater pumping outpaces recharge.

A recent Arizona Department of Water Resources report shows that the West Valley, including the city of Buckeye, is projected to be 4.4 million acre-feet short of what it needs for anticipated growth based on future pumping and recharge estimates. Because state law requires a 100-year assured water supply in this region, the agency can’t approve new development here.

“Despite years of study, officials have failed to analyze whether there’s enough water to justify this multi-billion dollar highway,” said McSpadden. “This threatens to be a massive waste of public money and it’s reckless for them to push forward. Instead, Arizona should encourage smart growth, divest from polluting highways and promote green transportation.”

Background
A July 2021 environmental analysis identified a preferred corridor for Interstate 11, which would run between the border town of Nogales and Wickenburg, Arizona, northwest of Phoenix. One of two alternative routes through Pima County goes through pristine desert alongside Saguaro National Park, Ironwood Forest National Monument, the Tohono O’odham Nation, Sonoran Desert National Monument and protected wilderness areas, as well the exurban and rural fringes of Tucson and Phoenix.

In April 2022 conservation groups sued the Federal Highway Administration to challenge its approval of Interstate 11. The suit said the agency failed to consider other transportation alternatives, such as rail, and sidestepped the required environmental review.