The U.S. Supreme Court weighed in Monday on a long-running water-rights fight between Wyoming and Montana, ruling that Wyoming shorted its neighbor to the north on Tongue River water for just two of the 15 years Montana had claimed.

The judgment by the nation’s high court upholds the conclusion by a court-appointed special master that Wyoming is liable to Montana for reducing the volume of water available in the river at the state line in 2004 and 2006. The court ordered the case back to the special master to determine damages and any other legal relief owed to Montana.

The justices ruled for Wyoming in claims made by Montana for 13 other years dating back to 1981.

Ranchers and farmers in both states depend on the Tongue River, which flows north from Wyoming and eventually joins the Yellowstone River. Montana sued in 2007, arguing that Wyoming for years had broken a 1950s-era water compact by allowing irrigators and small reservoir owners to take too much water from the Tongue.

The Supreme Court took jurisdiction over the dispute between states and appointed Barton Thompson, Jr., a Stanford University law professor, as special master to preside over the lawsuit.

The court ruled Wyoming owed Montana for a total of 1,356 acre feet of water in 2004 and 2006. That’s a relatively small amount for a river where 313,000 acre feet of water flows at the state line in an average year, according to Wyoming attorneys.

An acre foot is about 325,000 gallons. The state previously offered Montana $36,000 in compensation for the lost water.

“This is a good decision from the U.S. Supreme Court,” Wyoming Gov. Matt Mead spokesman David Bush said. “The governor hopes to have resolution on this matter soon.”

However, Montana will be seeking money and an order that will ensure Wyoming doesn’t short the state in the future, state officials said.

“Montana has believed all along that appropriate injunctive relief to prevent future violations by Wyoming was a critical component of the lawsuit,” Attorney General Tim Fox said in a statement. 

“Montana and Wyoming are neighbors sharing the resource, and a defined path forward as to how that sharing will occur is key to productivity on both sides of the border.”

Representatives for the two states had been in talks on how the Yellowstone River Water Compact will be administered in the future, but negotiations were on hold pending action by the Supreme Court, Fox spokeswoman Anastasia Burton said.