In an opinion Monday, the court is upholding a ruling by a special master appointed to oversee the case that the fees for expert witnesses should be about $163,000, not the $9 million sought by Kansas.
Colorado already had agreed to pay Kansas more than $34 million after the high court decided in 1995 that groundwater pumping in Colorado diverted millions of gallons of upstream water that rightfully belonged to Kansas.
Colorado Attorney General John Suthers called the ruling a "bright note" in the long-running case.
"We are glad to see the Supreme Court sided with our position on the matter of expert witness fees and, as a result, saved Colorado taxpayers more than $9 million," he said.
The witness fees have been in dispute since 2004.