Cle Elum Lake is part of the Columbia River basin, as the Cle Elum River is a tributary of the Yakima River, which is tributary to the Columbia River.
The lake is used as a storage reservoir for the Yakima Project, an irrigation project run by the United States Bureau of Reclamation. Although a natural lake, Cle Elum Lake's capacity and discharge is controlled by Cle Elum Dam, a 165 foot (50 m) high earthfill structure built in 1933. As a storage reservoir, Cle Elum Lake's active capacity is 436,900 acre feet (539,000,000 m³)., United States Bureau of Reclamation.