Floodwater Diversion    Photographer: Illustration by Jameson Simpson

Sounds sweet. Instead of letting the Mississippi River overflow its banks, how about sending a few billion gallons to the parched Southwest? The first barrier is the environment. Flooding regenerates farmland and cues fish to spawn, says Taylor Hawes, the Nature Conservancy’s program director for the Colorado River. There’s also the issue of invasive species infiltrating river systems. You really want to see Asian carp in the Grand Canyon?
Then there’s politics. East of the 100th meridian, it’s generally illegal to divert water from one basin to another, a fact that has prevented always-thirsty ­Atlanta from tapping the Tennessee River (which doesn’t enter Georgia). Even if laws were changed, politicians tend to protect their water sources. Grand County, Colorado, for example, home to the Colorado River’s headwaters, is grappling with a proposal to divert as much as 85 percent of its flows to Denver and the Front Range.
The biggest problem: cost. One proposal, floated in 2009 by Colorado rancher and mining engineer Gary Hausler, would create a pipeline from the Mississippi to the Colorado at an estimated $22.5 billion. That’s just to build the thing. You’d also have to factor in the annual cost, in money and energy, of pumping huge amounts of water uphill for roughly 1,200 miles.
But, says Southern Nevada Water Authority spokesman J. C. Davis, whose group has its own plans for less audacious regional diversions, “I bet if you went back and asked people about building a coast-to-coast highway system, they’d have mocked that, too.”