Tucked in the mammoth spending bill that Congress passed Monday night is a historic pact that will resolve thousands of water-rights claims by the Confederated Salish and Kootenai Tribes, provide nearly $2 billion for a major irrigation project and return the 19,000-acre National Bison Range to tribal ownership, more than a century after the federal government illegally carved it from the middle of the Flathead Indian Reservation.

The passage of the compact, which moved through Congress as the Montana Water Rights Protection Act, comes five years after the Montana Legislature narrowly approved a similar agreement with the CSKT. It was sponsored by Montana Sens. Steve Daines and Jon Tester and hailed as a bipartisan achievement that will provide for tribe-managed fish and wildlife conservation while protecting farmers and ranchers who depend on irrigation for their livelihoods.

"This is one of the most significant days in the history of our people and one that will have a profound and positive impact on the future of the Flathead Reservation for the next century," CSKT Chairwoman Shelly Fyant said in a statement.

According to Daines' office, the settlement permanently resolves 97% of the CSKT's claims against the federal government for decades of neglect and mismanagement of tribal lands and waterways. It provides more than $1.9 billion to settle damages and modernize the Flathead Indian Irrigation Project, relinquishes federal liens on irrigators and provides $10 million in road infrastructure funding to Lake and Sanders counties. And it strikes a delicate balance to protect water rights in streams that support critical fishery habitat and channels used for irrigation.

"This will conclude a very long and difficult effort to quantify the water rights of the Séliš Ql’ispé and Ksanka people," Fyant said. "This means we can avoid decades of acrimonious litigation on streams across much of Montana, and protect many streams with sufficient amounts of water to ensure fish can survive and Montana’s residents can recreate and fish as they have for generations."

Fyant expressed gratitude to Tester, a Democrat, for introducing a version of the compact in 2016 and Daines, a Republican, for reintroducing the legislation this year and working to push it through the GOP-controlled Senate. Montana's congressional delegation also persuaded party leaders to include the compact in the 5,600-page, $2.3 trillion catchall spending bill, which funds the government through September and also includes a $900 billion COVID-19 relief package.

President Donald Trump is expected to sign the bill, and afterward the CSKT would ratify the water compact.

"This victory has been decades in the making, and is a huge win for Montana taxpayers, ranchers, farmers and the tribes," Tester said in a statement. "Water is among our most valuable resources, and ratifying this compact honors our trust responsibilities, creates jobs and invests in infrastructure while providing certainty to water users everywhere. I’m thankful we were able to work together to get this critical legislation across the finish line."

Without the compact, Daines said thousands of Montanans would fight costly legal battles over water rights claimed by the CSKT, costing the agriculture industry more than $1 billion.

"That’s why we’ve worked so hard to pass our bill that will protect the water rights of all Montanans, save taxpayer dollars, create jobs, modernize rural infrastructure, protect Montana agriculture and prevent costly litigation," Daines said. "This is a win for all Montanans."

The National Bison Range will remain open to the public under CSKT trust ownership, and the tribes will permanently lead efforts to conserve bison herds and other wildlife after years of frustrating "self-governance agreements" with the U.S. Fish and Wildlife Service.

"The implementation of the settlement," Fyant said, "will create thousands of good-paying jobs and help boost our regional economy."

The Flathead Reservation was established as the CSKT's homeland in 1855 with the signing of the Hellgate Treaty, but portions of it were taken for non-Indian settlement in the early 1900s, and in 1908 the federal government established the Bison Range as a national wildlife refuge, paying the tribes only $1.56 per acre.

A federal court deemed that move unconstitutional in 1971, saying it was an illegal taking under the Fifth Amendment because the government did not pay fair market value for the land. The tribes were awarded about $232,000 in compensation, a figure based on 1912 land values.

Whitney Tawney, deputy director of Billings-based Montana Conservation Voters, called the new compact "the product of government-to-government collaboration, resulting in a fair and equitable solution for sovereign tribal governments and their lands, for Montana’s shared public lands, for bison and other wildlife, and for the precious resource of water.”

The passage of the compact also elicited celebratory statements from Republican Rep. Greg Gianforte, who will begin his term as Montana's governor next month, and Tim Fox, Montana's Republican attorney general, who opposed a 2013 draft of the agreement before supporting the version that made it through the Legislature in 2015.

"I cannot overstate the historic significance of this milestone in the 165 years since the signing of the Hellgate Treaty," Fox said in a statement.