The U.S. Supreme Court heard oral arguments this week in a complicated groundwater case that could have implications for the Mountain West.
The case involves Mississippi alleging that Tennessee is unlawfully taking water from an aquifer that runs beneath both states. It’s also seeking $600 million in damages.
Attorneys general from Colorado, Idaho, Wyoming and five other states wrote in an amicus brief that they support Tennessee, and don’t want to further complicate water law by opening up a new kind of lawsuit over groundwater. Several Western states already face decades-long conflicts over surface water alone.
Dylan Hedden-Nicely directs the Natural Resources and Environmental Law program at the University of Idaho. He explains that water rights above and below ground formed separately because, in the 19th century, groundwater wasn’t readily available.
“That changed in the 1940s, '50s, '60s with the advent of more efficient pumping mechanisms and cheaper electricity. But as a result of that, most states historically have exerted less control over groundwater use than surface water use,” he said.
Hedden-Nicely said that’s likely why there’s concern about a Supreme Court case dealing with an aquifer under multiple states.
“The concern would be, 'Well, now the Supreme Court is going to interfere with our ability to essentially use this water as much as we, and each individual state, want to,'” he said.
In the amicus brief, the states claim “strong interests because this case’s outcome could reshape established methods of determining states’ obligations to each other about natural resource use within their own borders.”
Interstate arguments over surface water often involve something called “equitable apportionment” to figure out how much water each state should get, which can involve complicated calculations and negotiations. However, it’s not clear whether or how that would apply to water underground.
If Mississippi were to win a case like this, and the Supreme Court rules that “equitable apportionment” applies, Hedden-Nicely said that would likely prompt more states to sue over their groundwater rights. That could also affect tribes with water compacts within a state.
“When litigation proliferates, usually if tribes have interests, then they have to get involved,” he said.
University of New Mexico law professor Reed Benson said he doesn’t think Mississippi has a great chance of winning. However, he said how Mississippi loses could have implications for Western states, too.
“(Western states) would like to see the court close the door on the kind of legal theory that Mississippi is advocating, and we could probably use some clarity on the law of interstate groundwater,” he said.
For example, he says the court could rule whether groundwater needs to be legally viewed like surface water, which would give some legal framework for future disputes.
No matter what happens with this case, climate change will likely increase friction between states over groundwater. And both Benson and Hedden-Nicely said that’ll likely mean more court battles down the line, especially if there aren’t clear ways to figure out how much groundwater each state or tribe needs and is entitled to.
This story was produced by the Mountain West News Bureau, a collaboration between Nevada Public Radio, Wyoming Public Media, Boise State Public Radio in Idaho, KUNR in Nevada, the O'Connor Center for the Rocky Mountain West in Montana, KUNC in Colorado, KUNM in New Mexico, with support from affiliate stations across the region. Funding for the Mountain West News Bureau is provided in part by the Corporation for Public Broadcasting.