The floodgates of the Oroville Dam opened a couple of minutes before 11 a.m. Tuesday and water rushed down the spillway into the Feather River for the first time since 2017, when the main and emergency spillways partially collapsed.

Officials were releasing 3,300 cubic feet per second, which sent a thin sheet of water cascading down the newly repaired main spillway before forming small waves and crashing into concrete barriers at the base to pour into the river.

State water officials were monitoring the release and reported no problems with the spillway.

“It’s operating as expected,” said Erin Mellon, communications manager for the Oroville Recovery project for the California Department of Water Resources.

State water officials who manage the dam said storms this week will probably force them to open the floodgates to control water levels in the reservoir, which is brimming after several winter storms and heavy snowfall in the mountains.

“This is not a test,” Mellon said. “It’s an actual use of the spillway due to projected levels in the coming days.”

Two storms are forecast to hit Oroville this week with peak rainfall arriving late Tuesday, followed by a stronger storm later in the week.

The reservoir, on the Feather River about 75 miles north of Sacramento, is currently three-quarters full, but if the storms fill it above safety levels and the spillway is needed, dam officials are confident the chute will hold.

The dam’s main concrete spillway failed so severely in February 2017 that nearly 200,000 residents were ordered to evacuate and officials employed the emergency spillway that poured water over a mostly barren hillside. It quickly eroded as the deluge cascaded down the hillside.

The state spent $1.1 billion repairing both spillways, reinforcing the concrete with 12.4 million pounds of steel rebar. The half-mile-long main spillway, where the initial fracture occurred, is now as wide as a 15-lane freeway and averages 7½ feet thick, compared with 2½ feet in the original 1960s version. It is capable of handling up to 270,000 cubic feet of water per second — far more than dam operators ever expect to release and 56% increase from the capacity of the old chute, which could handle only 160,000 cubic feet per second.

The new 3,000-foot-long spillway has steel pillars anchoring the structure 15 to 25 feet deep into bedrock and a modernized drainage system. The old spillway had only 5-foot-deep piles holding it in place.

The hillside that serves as the emergency spillway has also been reinforced with concrete and a retaining wall. It is unlikely to be used this week, dam officials said.

With the spillways reinforced, dam officials expect it to hold up well. They expect to increase the flow to 8,000 cubic feet per second by early afternoon.

“The main spillway has been fully reconstructed,” Mellon said. “We've used the best engineering minds and practices in the reconstruction and we have done it under the oversight of state and federal regulators and independent experts.”

Michael Cabanatuan is a San Francisco Chronicle staff writer. Email: mcabanatuan@sfchronicle.com Twitter: @ctuan