The U.S. Supreme Court ruled Monday that Wyoming irrigators are not taking more than their share of water from the Tongue and Powder rivers.
The court rejected, 7-1, Montana’s contention that improved irrigation methods used in Wyoming during the last 60 years have increased the Cowboy State’s water consumption in violation of the Yellowstone River Compact of 1950.
However, Montana’s lawsuit against Wyoming is far from resolved. Years of litigation lie ahead on other major components of this complex case brought to the Supreme Court four years ago.
Among the major issues remaining is whether the Yellowstone Compact governs the use of groundwater — something not clearly spelled out in the 1950 document. Montana contends that Wyoming is violating the compact with its more than 23,000 coalbed methane wells that disgorge millions of gallons of groundwater.
Monday’s ruling basically concerns sprinkler irrigation systems, which irrigators on both sides of the state line use. Those systems are more efficient than flood irrigation, which was more commonly practiced at the time the compact was approved. As a result, crops consume more of the water and less of it seeps back into rivers as return water.
That means that, in dry years, less water flows over the state line for Montana irrigators. Montana contends that sprinkler irrigation has reduced flows in the Tongue and Powder by 25 percent or more.
In a 20-page opinion authored by Justice Clarence Thomas, a majority of the court determined that Wyoming was not in violation of the compact on the irrigation issue.
“As long as no additional water is diverted from the stream and the conserved water is used on the same acreage for the same agricultural purposes as before,” the court agrees that there is no violation, he wrote.
The opinion concluded that “the doctrine of appropriation in Wyoming and Montana allows appropriators to improve the efficiency of their irrigation systems, even to the detriment of downstream appropriations.”
“While it’s hard not to be disappointed, it’s important to view this decision in perspective,” said Jennifer Anders, assistant attorney general for Montana. “We brought four claims, and the Court is allowing three of those to move forward.”
Pete Michael, chief deputy in the Wyoming Attorney General’s Office, said the remaining issues include groundwater, surface water priorities among water users and reservoir storage built after 1950.
“There is an extensive amount of scientific and detective work ahead,” he said. “It’s going to cost a lot of money. They have to go back years to find out who was using what water when.”
The compact was designed at the time to protect water rights established by 1950, although the amount each state was to receive was not specifically quantified.
Three tiers of users were established.
The first tier included those who had existing water rights in 1950. These users on both side of the line are to have priority when there isn’t enough water to go around. Second-tier rights are supplemental rights allocated to first-tier users. These post-1950 rights are not supposed to be used until all pre-1950 rights have been satisfied.
Finally, rights on the third tier divide any water left over. Third-tier water can be used directly on new acreage or diverted into reservoirs, once first- and second-tier users have taken their water.
Anders said Montana argues that Wyoming allows water allocations to post-1950 users before first-tier users in Montana get their share. Montana also claims that Wyoming is diverting water into new or expanded reservoirs before Montana rights are satisfied.
Those issues are before a special master appointed by the U.S. Supreme Court. He will handle the case, including any trial on the remaining issues, and submit recommendations to the Court. The court can accept or reject his conclusions in issuing its own decision.
In its ruling on Monday, the high court approved the special master’s recommendation on the irrigation issue.
Michael said the special master, Stanford University law professor Barton Thompson Jr. , will probably be in touch with both states soon to come up with a draft “discovery management plan” for the major issues still unresolved.
The discovery will probably include a lot of scientific data on both river systems and a lot of detective work to determine past patterns and uses, he said.
There have been no discussions of a settlement between the states, though neither side absolutely discounts the possibility. Both sides said they are preparing for trial.
“We’re just at the beginning,” Anders said.
Lorna Thackeray can be reached at 657-1314 or email@example.com