Moses Lake is a lake and reservoir located along the course of Crab Creek in the U.S. state of Washington. It is part of the Columbia River basin, as Crab Creek serves as a tributary to the Columbia River.
Originally a shallow natural lake, Moses Lake was dammed in the early 20th century for irrigation purposes. It subsequently became integral to the Columbia Basin Project, overseen by the United States Bureau of Reclamation. Moses Lake now receives water from Crab Creek and irrigated agricultural runoff. Previously, its water flowed into Crab Creek, but now it flows into Potholes Reservoir, formed by the impounding of Crab Creek at OSullivan Dam.
