Over the years, a proposed solution to Western water woes has come up again and again: large-scale river diversions -- including pumping Mississippi River water to the parched region.
Most recently, the Arizona Legislature passed a measure in 2021 urging Congress to investigate pumping floodwater from the Mississippi River to bolster flows in the Colorado River, its waters now locked in a seven-state debate to sharply reduce diversions from the shrinking river.
Studies and modern-day engineering have shown that such large-scale diversion projects are possible, but the effort would require decades of construction and billions of dollars. Politics likely are an even bigger obstacle for making multistate pipelines a reality. Yet the persistence of such plans in the public sphere illustrates the growing desperation of Western states to dig themselves out of prolonged drought.
"We can move water, and we've proven our desire to do it. I think it would be foolhardy to dismiss it as not feasible," said Richard Rood, professor of Climate and Space Sciences and Engineering at the University of Michigan. "But we need to know a lot more about it than we currently do."
Formal large-scale water diversion proposals have existed in the United States since at least the 1960s, when a U.S. company devised the North American Water and Power Alliance to redistribute Alaskan water across the continent using reservoirs and canals. But widespread interest in the plan eventually fizzled.
Stories of similar projects often share the same ending, from proposals in Iowa and Minnesota to plans between Canada and the U.S. Yet some smaller-scale projects have become reality.
A Kansas groundwater management agency, for instance, received a permit last year to truck 6,000 gallons of Missouri River water into Kansas and Colorado in hopes of recharging an aquifer. In northwestern Iowa, a river has repeatedly been pumped dry by a rural water utility that sells at least a quarter of the water outside of the state. And there are several approved diversions that draw water from the Great Lakes.
On the heels of Arizona's 2021 push for a pipeline feasibility study, former Arizona Gov. Doug Ducey signed legislation in July that invested $1.2 billion to fund projects that conserve water and bring more into the state. Among its provisions, the law granted the state's water infrastructure finance authority to "investigate the feasibility" of potential out-of-state water import agreements.
An in-depth feasibility study specifically on pumping Mississippi River water to the West hasn't been conducted yet to Larson's knowledge. He said he's open to one -- but doesn't think it's necessary.
"I think the feasibility study is likely to tell us what we already know," he said, "which is that there are a lot less expensive, less complicated options that we can be investing in right now," such as reducing water use.
In 2012, the Bureau of Reclamation, a subset of the Interior Department, completed "the most comprehensive analysis ever undertaken within the Colorado River Basin" at the time that analyzed potential solutions to regional water supply issues -- including importing water from the Missouri and Mississippi rivers.
Under a test scenario, water would be conveyed to Colorado's Front Range, an area roughly encompassing the eastern slope of the Rockies between the Colorado-Wyoming border and Arkansas River, including Fort Collins, Denver and Colorado Springs.
The scenario also conveyed water to areas of New Mexico. Overall, it was estimated at the time to cost at least $1,700 per acre-feet of water, potentially yielding 600,000 acre-feet annually by 2060 and taking three decades to construct.
An additional analysis emerged a decade later when Roger Viadero, an environmental scientist and engineer at Western Illinois University, and graduate students assessed proposals floated in a firestorm of letters to the editor at a California newspaper after reports of interest in diverting Mississippi River water to the region.
In their technical report, which hasn't been peer-reviewed, the researchers calculated that a pipe for moving this scale of water would need to be 88 feet in diameter -- about twice the length of a semitrailer. In the alternative, it would require a 100-foot-wide canal that's 61 feet deep.
"As an engineer, I can guarantee you that it is doable," Viadero said. "But there are tons of things that can be done but aren't ever done."
Viadero's team estimated that the sale of the water needed to fill the Colorado River's Lake Powell and Lake Mead -- the largest reservoirs in the country -- would cost more than $134 billion, at a penny a gallon. An untold price tag for construction would add to this hefty bill, along with the costs of powering the equipment needed to pump the water over the Continental Divide.
Other hurdles, meanwhile, include endangered species protections, wetlands protections, drinking water supply considerations and interstate shipping protections. Precedents set by other diversion attempts, such as those that created the Great Lakes Compact, also cast doubt over the political viability of any large-scale Mississippi River diversion attempt, said Chloe Wardropper, a University of Illinois Urbana-Champaign professor researching environmental governance.
Transnational pipelines would also impact ecological resources. Less Mississippi River flow means less sediment being carried down to Louisiana, where it's used for coastal restoration. Diverting that water also means spreading problems, like pollutants, excessive nutrients and invasive species.
Most notably, the Mississippi River basin doesn't always have enough water to spare. Drought conditions plagued the region throughout 2022, for instance, prompting concerns over river navigation and its ability to float freight.
"No one wants to leave the western states without water," said Melissa Scanlan, a freshwater sciences professor at the University of Wisconsin-Milwaukee. "But moving water from one drought-impacted area to another is not a solution."
This story was produced by the Mississippi River Basin Ag & Water Desk, an editorially independent reporting network based at the University of Missouri School of Journalism in partnership with Report For America and the Society of Environmental Journalists, with funding by the Walton Family Foundation.