The California Division of Water Resources began required flood control releases into the Feather River using Oroville Dam’s main spillway Monday, Jan. 5.

Oroville is the state’s second-largest reservoir, trailing only Lake Shasta. When full, Oroville holds 3.5 million acre-feet of water. In comparison, the San Louis Reservoir has a capacity of 2 million acre-feet.

Between mid-September and May, DWR is required to operate Lake Oroville for flood control under federal guidelines set by the U.S. Army Corps of Engineers.

These regulations establish a set storage space that is reserved to capture inflows from rain and future snowmelt, while protecting downstream communities from damaging flood events through coordinated releases.

To maintain this storage space, DWR must conduct flood protection releases from Lake Oroville. Some of the water released from Oroville for flood control is captured downstream for beneficial uses by local landowners, communities, and the State Water Project.

The 10-mile reservoir was at 77% capacity and 136% of its average level this time of year as of midnight Thursday.