FOR SEVEN YEARS, Nestlé's been gunning to siphon Columbia Gorge water and sell it. Lately, it's looked like their plan was airtight, but opponents may have found a leak: Native American water rights.

The fight to keep the Switzerland-based mega-corporation from getting rights to pristine Oxbow Springs water—which it wants to bottle and sell under its Arrowhead brand name—has mobilized environmental groups concerned about privatizing what is now publicly owned water and entering into a long-term contract with Nestlé, a company with an awful record on environmental stewardship.

With most of the state in a drought emergency, opponents have continued to fight what appeared to be a losing battle in January, when the Oregon Department of Fish and Wildlife (ODFW) agreed to a complicated water rights swap with the tiny town of Cascade Locks. The deal would circumvent a detailed "public interest review," granting Nestlé the access it's been gunning for.

In order for Cascade Locks to sell Oxbow Springs water to Nestlé, city officials are trying to trade water rights with ODFW: In exchange for taking 0.5 cubic feet of water per second from Oxbow, the city would give ODFW the same amount from Herman Creek aquifer.

It's proven difficult to poke holes in their plan, but it may not hold water after all.

Cascade Locks sits on aboriginal lands of the Confederated Tribes of Warm Springs. The tribe's 1855 treaty with the United States government established reservation boundaries and granted rights to tribal members to harvest fish and game from lands outside those boundaries.

Now it looks like those rights could be a viable way to block Nestlé's entrance into the Columbia basin. In May, E. Austin Greene Jr., Chairman of the Tribal Council of the Confederated Tribes of the Warm Springs Reservation, sent a letter to Governor Kate Brown requesting she reconsider allowing the swap without a public interest review.

"Water quantity and quality and hatchery operations are of paramount importance to ongoing treaty-based rights of the Tribe in the Columbia River area and to ongoing federal litigation," the letter reads. "These factors are not only reasonable to evaluate but of critical importance for ODFW's proposed water transfer, particularly in the context of climate change... and more frequent droughts and/or dry years."

Here's how water rights in Oregon work: The state is a "prior appropriation" jurisdiction, according to Michael Schultz, an attorney specializing in water rights. In layman's terms, this means it's first-come, first-served. When the demand on a certain water source exceeds the current flow, those who asserted a claim first take priority over those who made a claim later.

When there's a dispute over who's got senior rights, the Oregon Water Resources Department (OWRD) steps in to adjudicate. During the judicial process, parties present evidence showing how long they've been using the water, how much they need, and what it's for, Schultz says.

Tribes claiming water rights on ancestral lands use the term "since time immemorial" to describe a date that no one can pinpoint. In 2013, the Klamath Tribes—whose aboriginal lands encompass much of the Upper Klamath Basin in South Central Oregon and Northern California—won recognition of their senior rights from the OWRD under the same premise after a 38-year fight.

There's national precedent for such victories. In 1908, the U.S. Supreme Court determined that tribal water rights were preserved under any treaty in which a tribal reservation was formed. These are known as "Winters Rights," after the court case which created them, and are interpreted to include not only the right to divert water, but also to require water be left in streams and rivers at an amount necessary to support the fish on which tribes traditionally existed, such as salmon.

Though the Warm Springs tribes didn't comment when the OWRD solicited comments from the public on the proposed rights swap in the Gorge, Oregon statute allows anyone to protest a "preliminary determination" on the deal the agency is expected to make by the end of the summer, according to Maura Fahey, an associate attorney with Crag Law Center in Portland. Fahey has represented environmental watchdog groups Food and Water Watch and Bark in the water fight.

"The Department must consider the potential impacts of this change to downstream water users including tribal water and fishing rights," she wrote in comments to the OWRD. "All tribes with trust reservations within the Columbia River basin and its tributaries potentially have reserved water right claims that cannot be infringed upon."

Fahey says the tribe must be able to prove the water transfer could "cause injury" to their own water rights. Chairman Greene's letter makes that claim, and Fahey's comments support his assertion.

The water that ODFW currently takes from Oxbow Springs is cycled through the Oxbow Fish Hatchery, located just outside Cascade Locks, and returned to the watershed. If Nestlé gets its way, the water would be permanently removed from the basin. Fahey's firm argues this permanent removal is injurious to other rights holders, but Schultz says proving injury can be tricky.

Greene's letter was a formal plea to Governor Brown, who has the power to stop the process by instructing ODFW to withdraw its application from OWRD. Julia DeGraw, Northwest Senior Organizer for Food & Water Watch, a Washington DC-based group that's been fighting Nestlé since the beginning, says she thinks Brown is making a political mistake by not addressing the issue.

"It's disingenuous of her, at best," DeGraw says. "I think it's also a huge miscalculation on her part as a political stance because people would applaud her for taking a stand against a company that's ignored the rules in so many other places."

The pleas come as the governor grandstands about Oregon's tenuous water situation. On July 7, Brown declared July "Water Awareness Month," and issued a statement asking "all Oregonians to do their part to use water wisely."

"Water is the foundation for local economies and ecosystems, and essential to the health and well-being of Oregonians," she wrote. "Drought is a slow moving disaster, adopting responsible water use practices now will help reduce the impact of drought for years to come."

On July 21, Brown added Hood River County—home to Cascade Locks—to the list of areas experiencing a drought emergency.

Now, she's demanding "state agencies to step up efforts to conserve water." On July 28, Brown issued a formal executive order demanding that all agencies report back by November 1 on their progress toward reducing water consumption by 15 percent, and update their plans for drought by investigating "potential new tools to help communities deal with the impacts of water shortages," according to a news release.

It's clear the governor understands the state's dire water outlook. But DeGraw thinks Brown's cautions to Oregonians ring hollow when she's simultaneously unwilling to put the brakes on ODFW's proposed water swap.

Chris Pair, Brown's press secretary, says the governor won't be stepping in on the issue, and that opponents would be best served by trying to get Cascade Locks' city administrators to change their minds.

"The state will not be a party, and since this is a local decision under current law, the role of the Governor's Office is fairly limited," Pair responded via email. "Regardless, Governor Brown expects Oregon's state agencies to follow all laws and regulatory processes to the letter."

The OWRD is currently reviewing public comments on the proposed swap, and spokeswoman Racquel Rancier says they expect to issue a preliminary determination soon. That determination will initiate a 30-day period in which any person can file a protest, which could then be heard in front of an administrative law judge.

In the meantime, other concerned Warm Springs tribal members, like Annamae Leonard, are getting involved on a grassroots level.

"None of us even knew about Nestlé until recently," Leonard said during a July 4 protest in Cascade Locks. "We really thought the environmental and citizen groups had it under control, but if they don't then the tribe needs to assert its water and fisheries rights."