HELENA — A legislative working group came to its final meeting Tuesday armed with a 100-page report that says the scientific modeling used in the state’s water-rights compact with the Confederated Salish and Kootenai Tribes is reasonable.

The CSKT Compact Technical Working Group approved the report after months of reviewing scientific and technical information on which the compact is based.

“We’ve put in a lot of work,” said the group’s chairman John Metesh, the director of the Montana Bureau of Mines and Geology. “It’s a pretty good draft report of findings.”

The report said additional modeling will be needed for irrigators to operate practically under the terms of the compact.

The Legislature’s Water Policy Interim Committee asked for expert review after the compact presented to the 2013 Legislature was rejected. The six-person group also included those from the Bureau of Mines and Geology, Montana Fish, Wildlife and Parks and the Montana Department of Natural Resources and Conservation.

The legislative committee could use the report to draft and present a compact during the 2015 Legislative session.

After at least a decade of negotiations, a water-rights compact presented and rejected by the 2013 Legislature prompted lawsuits over claims to the water flowing on or through the northwestern Montana reservation.

The 2015 session is the final chance for lawmakers to approve the compact. If they fail, the tribes will have to assert their water rights by filing claims in a state stream adjudication court by June 30, 2015.

Who controls water flowing on or through the reservation and how much goes to farmers, ranchers and others through the Flathead Indian Irrigation Project has been at the core of the dispute.

At the working group’s meeting, rancher Jerry Laskody said he’s concerned about parts of the report that hold irrigators to certain measurement standards that he said may not be accurate.

“It’s very important to get these irrigation requirements down accurately,” he said. “I think some of this water quantification is suspicious.”