Montana Attorney General Tim Fox says some farmers and ranchers are being denied their "lifeblood" by upstream water users in Wyoming taking more than their share from the Yellowstone River basin.
But as a trial in the interstate dispute began Wednesday, an attorney for Wyoming accused Montana of wasting enough water to more than satisfy its needs.
Wyoming Senior Assistant Attorney General James Kaste said in opening arguments that Montana needlessly allows water to bypass the Tongue River Reservoir instead of capturing it for future use.
Fox says the issue is a red herring, meant to divert attention from Montana's claim that Wyoming violated a 1950 water sharing agreement.
The U.S. Supreme Court appointed Stanford Law School professor Barton Thompson, Jr. to oversee the trial. It's scheduled to last weeks.