Topeka ? Kansas threatened a court fight Wednesday unless Nebraska cuts its use of water from the Republican River and pays millions of dollars for taking too much in 2005 and 2006.

But Nebraska officials said their state already is trying to come into compliance with rules on water use set by the U.S. Supreme Court. And Kansas’ demands would force Nebraska to shut down wells for more than 40 percent of the irrigated acres in its part of the river basin.

Kansas alleges that Nebraska’s water use exceeded what was allowed for the two years by about 27 billion gallons – or enough to supply a city of 100,000 for 10 years.

Kansas Attorney General Paul Morrison and the state Division of Water Resources sent letters to Nebraska Attorney General Jon Bruning and Ann Bleed, director of that state’s Department of Natural Resources.

Morrison spokeswoman Ashley Anstaett said Kansas attorneys are still trying to determine exactly how much Nebraska should pay Kansas. She said the amount will represent either the harm suffered by Kansas or the gain to Nebraska from using too much water.

But David Barfield, the chief engineer for the Division of Water Resources, said the money sought by Kansas is “certainly in the tens of millions.”

Barfield said cutting irrigation as much as Kansas demands would require shutting down wells that water about 500,000 acres of the roughly 1.2 million irrigated acres in its portion of the Republican River basin. Kansas seeks the immediate shutdown of wells within 2.5 miles of the Republican River and its tributaries, as well as land in the basin where irrigation started after 2000.

“I don’t think there’s any question that they’ve overused the water,” Anstaett said. “We believe that our remedy package is fair and will begin to get them on the right track with compliance.”

Water use from the Republican River is governed by a 2003 decree from the U.S. Supreme Court, which approved a settlement among Kansas, Nebraska and Colorado of a lawsuit filed by Kansas in 1998.

In his letter, Morrison indicated that Kansas may file a lawsuit if Nebraska doesn’t agree to its demands.

“Absent such a resolution, we will have no choice but to pursue a litigation solution,” Morrison wrote.

Bleed declined comment, but Bruning called the letters from Kansas “another step in the process of resolving this dispute.”

He said that he hopes it can be resolved without a lawsuit and that he is confident Nebraska will achieve compliance without the “drastic actions” proposed by Kansas.

“However, if Kansas decides to pursue litigation, we are prepared to vigorously defend the interests of Nebraska and our citizens,” Bruning said.

Kansas Rep. Tom Sloan, R-Lawrence, said issues could drag out in court for several years, but he said it was necessary because Nebraska is having legal issues getting local irrigators there to stop pumping water from the ground near the river.

“Nebraska needs to have the Supreme Court say: ‘You will do this.’ Then they’ll be able to get it done,” Sloan said.