Carter Lake

Carter Lake is the second largest reservoir in the Colorado-Big Thompson Project East Slope distribution system and the principal reservoir for C-BT Project deliveries to the south and east. Construction occurred between July 1950 and September 1952 and cost $3.7 million.  

Carter Lake’s water originates in the headwaters of the Colorado River in the C-BT Project’s West Slope collection system. After flowing beneath the Continental Divide via the Adams Tunnel, water travels to Flatiron Reservoir where it is pumped 297 vertical feet through the 1.4-mile Carter Lake Pressure Tunnel to Carter Lake.   

Deliveries from Carter Lake are made via the Southern Water Supply Project pipeline to municipalities including Louisville, Superior and the City and County of Broomfield. The pipeline also stretches east to Fort Lupton, Hudson and Fort Morgan. 

Several cities, including Longmont and Boulder receive water from Carter Lake. The St. Vrain Supply Canal also delivers water from Carter Lake to irrigated farms and ranches in Boulder and Weld counties. 

The Robert V. Trout Hydropower Plant at Carter Lake started producing power in May 2012 and averages 7 to 10 million kilowatt-hours of clean energy each year. 

Completed in 2008 at a cost of $12 million, a multi-tiered second Carter Lake outlet provides valuable operational flexibility.  

Carter Lake has a capacity of 112,230 acre-feet, 1,110 surface acres, 12 miles of shoreline and a maximum depth of 180 feet.