Lake River, a "slow, flat slough of the Columbia River", loses only in elevation over its entire course. It flows north, roughly parallel to the Columbia until curving slightly northwest to join it. At times, tidal fluctuations and high flows along the Columbia cause Lake River to flow backwards into the lake, sometimes for long periods. Flowing out of the lake and Vancouver Lake Park, the river receives Buckmire Slough from the
left. Beyond the confluence, Shillapoo Wildlife Area is to the left, and the unincorporated community of
Felida is to the
right. About further downstream,
Salmon Creek enters from the right. Over the next , the river passes between
Curtis Lake on the right and Round Lake on the left. About from the
mouth, Lake River enters Ridgefield National Wildlife Refuge and passes between Green Lake on the right and Post Office Lake on the left. Whipple Creek enters from the right at RM 7 (RK 11). Over the next , Campbell Lake is on the left. Flume Creek enters from the right about from the mouth. The river exits the wildlife refuge, and about from the mouth, the stream curves to the northwest and enters Ridgefield, which is on the right. A mile or so later, Bachelor Island Slough enters from the left, and Carty Lake is on the right as the stream re-enters the wildlife refuge. Lake River enters the Columbia River at the north tip of Bachelor Island, about upstream of the mouth of the Lewis River and about from the Columbia's mouth on the Pacific Ocean. ==Watershed and water quality==