Marston Lake, reservoir in Denver, Colorado, United States

Marston Lake is a reservoir near Denver that supplies water to the city through its treatment and distribution system. Water flows in from the South Platte River and is directed to a treatment plant before traveling through pipes to homes and businesses throughout Denver.

The lake was built in 1902 by Denver Water to supply the growing city with water. Over the decades it became a key part of Colorado's water management system and continues to serve the community's needs.

Marston Lake is owned by Denver Water, the utility that built the reservoir in 1902 and still sends its water to the Marston treatment plant. The lake takes its name from the Marston treatment works it supplies, not from a settler. Its water arrives from the South Platte River, which is fed from the Colorado Western Slope through the Roberts Tunnel.

The lake is open year-round during daylight hours but has no official facilities or parking areas on site. It is best viewed from a car or by finding nearby trails while respecting private property boundaries along the shore.

Marston Lake records Colorado extremes: 104 °F (40 °C) on July 18, 1998, and −19 °F (−28 °C) on December 31, 2014. It lies at 1,684 m and covers about 2.4 km², stretching roughly 1.6 km north to south and 2.3 km east to west. Doublehead Mountain rises 18.1 km to the east.