An irrigation district hopes to persuade the Oregon Supreme Court its planned reservoir was wrongly blocked due to a misinterpretation of in-stream water rights law.

The state’s highest court is considering whether a reservoir proposed by growers from the East Valley Water District would unlawfully inundate stream flows meant to protect cutthroat trout.

The irrigation district argues the legal controversy doesn’t just affect its proposed dam near Silverton, Ore., but would upend how water rights are administered throughout the state.

“Unfortunately, this case has morphed into one that’s destabilized foundational principles of the prior appropriations system,” said Merissa Moeller, attorney for the district, during recent oral arguments.

Under the prior appropriations doctrine, the quantity of water available to senior water rights holders cannot be infringed by users with more junior rights.

Project shut down

However, the East Valley Water District claims its reservoir project was shut down to protect an in-stream water right based on subjective factors that shouldn’t have been considered.

“It has inserted unpredictability into a system that relies on predictability to manage Oregon’s limited water resources equitably on behalf of all water users,” Moeller said.

For example, the Oregon Association of Nurseries fears the interpretation could preclude new irrigation appropriations in any waterway with in-stream water rights, or complicate water transfers.

An application for the project near Silverton, Ore., was rejected by state water regulators because the associated flooding would violate the environmental purpose of an in-stream water right in Drift Creek.

That regulatory decision was affirmed by the Oregon Court of Appeals last year, but the irrigation district now claims the ruling improperly considered factors other than stream flow quantity, which would remain unaffected by the dam.

“What matters is whether that right is receiving the quantity of water to which it’s entitled,” Moeller said.

An opening in the structure would ensure that flows continue at a rate protected by the in-stream right, which should’ve warranted the storage project’s approval under state water law, according to the district.

The effects on fish and riparian habitat should be weighed under other statutes and regulations, as lawmakers meant for in-stream rights to focus solely on stream flow quantity, the district claims.

“It isn’t intended to a be a regulatory tool that solves all habitat issues,” Moeller said.

Subjective factors

Various types of water rights are all regulated according to quantity to provide a level playing field to water users, but using subjective factors would subvert that process, she said.

“We ask the state to use an objective measure to ensure the rules apply fairly to everybody,” she said.

The state Water Resources Department countered that fish habitat would effectively be “drowned” by the reservoir, which is a valid reason to reject the proposal.

“What we are talking about here is the destruction of the senior water right,” said Denise Fjordbeck, attorney for the government.

The agency considered the reservoir’s potential injury to the in-stream water right as the first step in its analysis, followed by a review of the public interest impacts as required by law, she said.

Though the project wouldn’t impair the quantity of water, it would nullify the in-stream right’s goal of securing habitat for cutthroat trout in the creek, Fjordbeck said.

“There are other attributes of the right that are protected,” she said.

Regulators have always been allowed to consider the public interest in evaluating water rights applications, but those proposals have traditionally involved consumptive uses that didn’t involve flooding, Fjordbeck said.

A singular situation

For that reason, “it hasn’t been necessary for the department to take that extra step,” Fjordbeck said. “We’re faced here with a singular situation and how to apply statutes to that singular situation.”

WaterWatch of Oregon, an environmental nonprofit, argued that lawmakers didn’t intend for junior rights to invalidate the purpose of senior in-stream water rights.

Allowing the reservoir would not only frustrate the purpose of the in-stream right on Drift Creek, but would allow similar projects to impair in-stream water rights elsewhere, said Tom Christ, the nonprofit’s attorney.

“This is about all the water courses in Oregon, including some of the most famous ones,” he said.