Mirabel Inflatable Dam on the Russian River. (Photo courtesy of Sonoma County Water Agency)

A rubber dam designed to protect drinking water supplies for hundreds of thousands living along the Russian River is being reinflated this week after an unexpected spring storm caused it to be deflated.

The Sonoma County Water Agency raised the Mirabel Inflatable Dam near Forestville on May 6 as river levels dropped and demand for water increased. The dam was lowered May 16 to protect it from high river flows that could damage its structure. The Water Agency started re-inflating the dam last Wednesday and it was expected to be fully inflated by early this week, spokesman Barry Dugan said.

Boaters will have to transport their vessels around the rubber dam located downstream of Wohler Bridge, and signs will be posted warning the public not to recreate on or near the dam, Dugan said. Fishing also is prohibited within 250 feet of the dam.

The rubber dam is critical to the supply of naturally filtered Russian River drinking water for more than 600,000 residents of Sonoma and Marin counties. The dam will remain inflated into the fall.