HORNBROOK, Calif. — The corporation in charge of deconstructing four dams on the Klamath River in Northern California and Southern Oregon began draining the reservoir behind Iron Gate Dam on Thursday.

Water from the Iron Gate Reservoir in Northern California is being released in a controlled manner through a low-level outlet tunnel, according to Ren Brownell, a spokeswoman for the Klamath River Renewal Corporation, which is coordinating the dam-removal process.

“There was a plug of sediment at the initial opening of the gate that cleared up in about an hour, though river residents can expect to see more sediment in the river over the coming days as it is stirred up in the reservoir and makes its way downstream,” Brownell said. “Things went really well.”

It’s expected that the reservoirs behind the Iron Gate, J.C. Boyle and Copco 1 dams will be completely drained by the end of February in preparation for their removal. A fourth dam, Copco 2, was removed last year. J.C. Boyle, west of Keno Dam, is the only Southern Oregon dam in the project.

Brownell said the reservoirs may refill a bit in March and April if there is significant spring runoff. Work to dismantle the dams is expected to begin in May or June, depending on the weather, and finish by fall.

Among those on hand for Thursday’s initial drawdown was Mark Bransom, CEO of the corporation.

“Witnessing the beginning of drawdown at Iron Gate dam was both celebration of an important moment in the story of Klamath dam removal and a source of pride for the exceptional work done by so many people to arrive at this day,” Bransom said in a written statement.

KRRC said in a release: “Communities downstream of the dams will start to see changes in the river in the coming days, as sediment that has accumulated behind the dams is evacuated downstream. There is an estimated 17 to 20 million cubic yards of sediment behind Iron Gate, JC Boyle and Copco No. 1, the three remaining Klamath dams slated for removal.”

In addition, the release said, “Extensive testing done by the U.S. Environmental Protection Agency and KRRC consultants has determined the sediment to be nontoxic, mostly consisting of dead algae, gravels and fine clay particulates.”

Recent storms that have increased water flow on the Klamath River are expected to help flush out sediment and carry it downstream.

Bransom said the drawdown at Iron Gate is different than at Copco 1 and J.C. Boyle, and different from what people may have seen with other dam removals.

“There was no blast at this dam,” he wrote. “Instead we had the opportunity to use existing infrastructure, which allows us to precisely control the volume of water going downriver, limiting downstream impacts.”

KRRC said in the release that the initial drawdown period was carefully selected by the corporation’s Aquatic Resources Working Group, which comprises tribes, state agencies and federal agencies. January and February are ideal months, the release said, because there are relatively few threatened and endangered species in the mainstem, and the relatively heavy winter flows can help carry sediment downstream.

The release said, “Water quality is expected to improve in March, after the initial phase of drawdown is complete, but it will likely take up to 24 months for water to return to usual clarity, following the successful establishment of vegetation in the former reservoir footprint areas.”

Hundreds of workers will be involved in the process of preparation, deconstruction and restoration.

The KRRC is a nonprofit formed in 2016 by 23 signatories of the amended Klamath Hydroelectric Settlement Agreement. The organization describes itself as being “part of a cooperative effort to re-establish the natural vitality of the Klamath River so that it can support all communities in the Klamath Basin.”

Signatories — which include the states of California and Oregon, local governments, tribal nations, dam owner PacifiCorp, irrigators and several conservation and fishing groups — appointed the corporation to take ownership and oversee removal of the four hydroelectric dams on the river.