In anticipation of the major storm that hit the Bay Area on Sunday, a rubber dam in the Russian River near Forestville was deflated this weekend to prevent damage to the dam from high river flows, authorities said.

Sonoma Water, Sonoma County’s water agency, deflates the rubber dam when Russian River flow forecasts show the river reaching 2,000 cubic feet per second, the agency said. The atmospheric river that arrived in the Bay Area on Sunday was expected to raise river flows above 19,000 cubic feet per second.

The rubber dam is just downstream of the river’s Wohler Bridge and is usually raised in the spring or early summer when water demands increase. It creates a pool of water that enhances Sonoma Water’s well levels in the area, the agency said.

A permanent “fish ladder,” a seemingly oxymoronic phrase describing a structure that helps fish navigate obstacles, provides fish passage when the dam is raised. The fish ladder also allows Sonoma Water to count the migration of adult salmon and steelhead with its underwater video system.

When completely deflated, the rubber dam — which holds water rather than air — rests flat on the bottom of the Russian River.

The agency noted that even with the recent series of storms, the region is well behind normal rainfall totals and reservoirs remain at historically low levels.