BILLINGS, Mont. (AP) — A legal clash over water rights on the arid Northern Plains goes to trial this week as attorneys for Montana press their case that Wyoming farmers and oil and gas companies are sucking too much water from tributaries of the Yellowstone River.

Montana sued its southern neighbor in 2007. It claims Wyoming is violating a 1950 agreement by depleting the Tongue and Powder Rivers before they flow north into Montana.

Among the contested issues is whether natural gas drilling in Wyoming is draining underground aquifers that feed the two rivers.

A weekslong trial to determine if Wyoming should be held liable begins Wednesday in a federal courtroom in Billings. The U.S. Supreme Court has appointed Stanford Law School professor Barton Thompson Jr. to oversee the case.