There are at least nine named lakes and reservoirs in Petroleum County, Montana .
A lake is an area filled with water, localized in a basin, that is surrounded by land, apart from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, and therefore are distinct from lagoons, and are also larger and deeper than ponds, though there are no official or scientific definitions. Lakes can be contrasted with rivers or streams, which are usually flowing. Most lakes are fed and drained by rivers and streams.
A reservoir is, most commonly, an enlarged natural or artificial lake, pond or impoundment created using a dam or lock to store water.
Petroleum County is a county in the U.S. state of Montana. As of the 2010 United States Census, the population was 494, making it the least populous county in Montana and the seventh-least populous in the United States. Its county seat is Winnett. The county's area was partitioned from Fergus County to become the last of Montana's 56 counties to be organized.
