A yearslong effort to purchase two of the most powerful water rights on the Colorado River has cleared another hurdle after the state water board agreed to manage the rights alongside Western Slope water officials.

The Colorado Water Conservation Board voted unanimously Wednesday night to accept the two water rights tied to the Shoshone Power Plant into its environmental flow program. The approval is a critical piece in the Colorado River District’s $99 million deal with the owner of the aging plant in Glenwood Canyon — Xcel Energy — but the deal has faced pushback from Front Range water providers that fear the change could impact their supplies.

Backers of the deal aim to make sure the water now used by the small hydroelectric plant — and then put back in the river — will always flow westward.

“The importance of today’s vote cannot be overstated as a legacy decision for Colorado water and the Western Slope,” Andy Mueller, general manager of the Colorado River District, said in a news release. “It secures an essential foundation for the health of the Colorado River and the communities it sustains.”

Colorado water officials hailed the decision as a monumental achievement for the state that will help protect the river and its ecosystem. The state’s instream flow program allows the Water Conservation Board to manage dedicated water rights for the health of rivers, streams and lakes.

“Acquiring the Shoshone water rights for instream flow use is a once-in-a-lifetime opportunity to preserve and improve the natural environment of the Colorado River,” Dan Gibbs, the executive director of the Colorado Department of Natural Resources, said in a news release.

One of the main sticking points during the hourslong meeting Wednesday was whether the board should manage the water rights with the River District. That would include decisions on how and when to require upstream users — like Front Range utilities — to send more water downstream. Generally, the board is the sole manager of water rights in its instream flow program, which the Shoshone rights are now a part of.

Several Western Slope entities said they would withdraw their financial support from the purchase if the Colorado River District was not allowed to co-manage the right with the board. Local governments and other organizations across the Western Slope promised more than $16 million toward the purchase.

Front Range water providers argued that the statewide board is the sole authority that can manage such rights and should have final decision-making power.

The water board instead approved the co-management strategy, which means that the two authorities will decide together how to act when there is not enough water to meet the right’s obligations.

The Colorado River District — a taxpayer-funded agency that works to protect Western Slope water — wants to purchase the Shoshone rights to ensure that water will continue to flow west past the plant and downstream to the towns, farms and others who rely on the Colorado River, even if the century-old power plant were decommissioned.

A stream of Western Slope elected officials, water managers and conservation groups testified in support of the deal and the rare opportunity it presented.

“The Shoshone call is one of the great stabilizing forces on the river — a heartbeat that has kept our valley farms alive, our communities whole and our economies steady even in lean years,” Mesa County Commissioner Bobbie Daniel said, urging the board to approve the plan.