Wikia

Lakes are inland bodies of water.

They occur when water has filled a large or small basin to capacity and is constantly fed by large or small river. They were smaller than seas and could be of fresh or salt water.

In the world of Arda, lakes were formed by the many upheavals, tumults, and disasters caused by the changes of the world after the marring by it by Melkor and by the forces of the Valar vanquishing him or by the direct intervention of Eru Ilúvatar.