Colorado asks Supreme Court to reject Nebraska's South Platte River lawsuit, calling it 'premature and unfounded'

Elise Schmelzer, The Denver Post on Oct 15, 2025

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DENVER — Colorado’s top leaders on Wednesday were not short on adjectives to describe Nebraska’s petition asking the country’s highest court to weigh in on a long-simmering water dispute between the states.

Attorney General Phil Weiser called the Cornhusker State’s filing over the South Platte River Compact “baseless” during a news conference announcing Colorado’s legal response. The canal Nebraska wants to build here, he said, is an “unserious boondoggle.” Gov. Jared Polis called the neighboring state’s filing premature, unfounded and a “meritless escalation.”

Their remarks came the same day Weiser filed Colorado’s response to Nebraska’s request for the U.S. Supreme Court to weigh in on its plans to build a canal in Colorado. The canal would divert more water from the South Platte River to Nebraska.

In the brief, Weiser argued that it was too early for the court to weigh in on the issues and that there were venues besides the high court to settle any differences.

“These hypothetical concerns they’ve raised do not warrant Supreme Court review,” Weiser said at the news conference. “They do warrant more conversation.”

Nebraska's state leadership sued Colorado on July 16, asking the Supreme Court to weigh in on two issues: the process by which Nebraska can use eminent domain to seize land in Colorado to build the canal and whether Colorado is sending enough water over the border to meet its obligations under the century-old compact. The petition and Nebraska's canal plans have sown uncertainty among the agricultural communities in northeast Colorado that rely on the river's water for their crops and way of life.

Colorado's response claims that Nebraska's request to the Supreme Court is too early — "unripe and premature." Nebraska lacks finalized plans for the canal, has failed to provide evidence that Colorado is not meeting its compact obligations and has not started the eminent domain process that it is asking the court to opine on, according to the brief.

"While it is possible that someday Nebraska and Colorado will have a dispute over the compact that warrants this Court’s engagement, that day has not yet arrived," the brief states.

Weiser, Polis and the state's top water official — state engineer Jason Ullman — denied Nebraska's claims that Colorado interfered in its attempts to build the canal and denied the allegations that Colorado is not meeting the requirements of the compact.

The two states were meeting regularly to discuss the canal and the compact before Nebraska filed its lawsuit — which took state officials by surprise.

"We thought that Nebraska would continue to engage with us to resolve these questions, as we've done for over 100 years," Ullman said Wednesday. "Up until Nebraska filed this petition with the Supreme Court, the two states had found ways to resolve whatever questions came up between them."

He expressed hope that they would resume those talks.

The South Platte River originates in the Front Range mountains before flowing through Denver and cutting across the northeast portion of the state and into Nebraska. It is a critical water source for Front Range cities, and more than 85% of the state’s population lives in the river basin. The river also irrigates more than 850,000 acres of farmland — the highest concentration of irrigated acres of any river basin in Colorado.

Nebraska leaders resurrected the long-dormant plans for the canal in 2022 after Colorado water leaders outlined plans to use and store more water from the river. Nebraska lawmakers set aside $628 million for the project, which would allow that state to divert water from the South Platte outside of the irrigation season.

Colorado leaders concede that Nebraska is legally allowed to build the Perkins County Canal — including by using eminent domain to seize Colorado landowners' property. That right is part of the 1923 compact that outlines how the two states share the South Platte's water.

Colorado has done nothing to stop Nebraska from pursuing the purchase or seizure of the Sedgwick County land needed for the canal, Weiser said, but the state maintains that Nebraska must pursue any eminent domain claims through Colorado's systems — which Nebraska disputes.

The Supreme Court will decide by July whether to take up all or some of Nebraska's claims, Weiser said.

If the court accepts the case, it will appoint a special master to oversee discovery and propose legal findings to the justices. The findings could prompt a settlement between the states. If they don't, the Supreme Court justices would use the findings — and any objections filed by the states — in their decision.

The process would take years, Weiser said.

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