water released from the upper feather river system flows into lake oroville, which is formed by the oroville dam several miles above the city of oroville. at , oroville is the tallest dam in the united states; by volume it is the largest dam in california. authorized by an emergency flood control measure in 1957, oroville dam was built between 1961 and 1967 with the reservoir filling for the first time in 1968.