Carter Lake is a reservoir located in the foothills northwest of Berthoud and southwest of Loveland. Created by three dams, it is approximately three miles long, with twelve miles of shoreline, a maximum depth of 180 feet, and a capacity of 112,228 acre-feet. The federal government built the reservoir in 1950–52 as part of the Colorado–Big Thompson Project, and it is the second-largest reservoir in northeast Colorado after Horsetooth Reservoir in Fort Collins.

Carter Lake serves the important function of bringing water from the Western Slope to the St. Vrain, Boulder Creek, and South Platte River basins that supply cities such as Boulder, Longmont, and Fort Morgan. The US Bureau of Reclamation owns the reservoir, while the Northern Colorado Water Conservancy District is responsible for operating and maintaining it. The Larimer County Department of Natural Resources manages recreational offerings on the water and more than 1,000 acres of surrounding public lands.

Before the Dams

The valley that would become Carter Lake was first a small wetland. Indigenous people—including the Arapaho, Cheyenne, and Ute people—initially occupied the area. They left numerous fire rings on the southern-facing slopes. White immigrants in the area referred to the valley as Carter’s Glade as early as the 1850s. The glade was named after homesteader Matthew Carter, whose land made up the northern portion, while a small natural lake called Blore Lake occupied the southeastern portion of the present-day reservoir. Carter’s Glade and Blore Lake offered several economic and recreational opportunities during the late nineteenth century. Matthew Carter and his son quarried and burned limestone from the area, which had a variety of uses in agriculture and construction. Ranchers used the area to graze cattle and often clashed with those hoping to hunt the numerous ducks found in the wetlands. Residents in Loveland and Berthoud also established a rock quarry on the east side of the present-day lake for local building projects.

Construction

During the 1930s, many rural communities in eastern Colorado suffered from severe drought and dust storms that devastated agricultural efforts throughout the high plains. From 1933 to 1940, under the New Deal, the Bureau of Reclamation took on many large water development projects , highlighting the important role of the federal government in supporting Colorado’s economy during and after the Depression. In 1937 the Colorado–Big Thompson Project was authorized to bring essential water from west of the Continental Divide to irrigate Colorado’s northeast plains. That same year, the Northern Colorado Water Conservancy District was created to be the local partner for the US Bureau of Reclamation on the project. Plans to construct a reservoir in the natural basin in the foothills west of Loveland and Berthoud began in 1937.

Reclamation engineers began construction of Carter Lake shortly after Horsetooth Reservoir (also part of the Colorado–Big Thompson Project) was finished in 1949. Before construction started, at least two buildings, including the Meadow Hollow School, had to be moved from the area (today the school sits in the Berthoud Historical Society’s Pioneer Courtyard). Carter Lake’s construction started in July 1950 and finished in September 1952 at a total cost of $3.7 million. The reservoir is formed by three dams on its eastern side. These dams are made of different types of shale, limestone, and sandstone. Once the land was clear and the dams built, water was pumped from Flatiron Reservoir—which holds water from the headwaters of the Colorado River—to Carter Lake via the 1.4-mile Carter Lake Pressure Tunnel. During construction, many of the workers lived in Loveland, while others opted to live in nearby Berthoud, boosting the small town’s economy.

Adjusting for Growth

Initially, Carter Lake delivered water primarily to farms during the irrigation season from April to October. As Colorado’s Front Range population grew, Northern Water had to make adjustments. In 1993 Northern Water began the Southern Water Supply Project to bring water to growing suburbs such as Broomfield. By 1995 the pipeline from Carter Lake south to Louisville, Superior, and Broomfield was complete, and another section of the pipeline brought water east to Fort Lupton, Hudson, and Fort Morgan after 1999. Population growth created more demand for year-round deliveries and prompted Northern Water to develop a multitiered outlet for greater operational flexibility in 2008. This outlet brings water year-round from Carter Lake to communities in the southern and central parts of the district’s boundaries, which extend from Boulder to Fort Collins and east along the South Platte River to Sedgwick.

By the late 2010s, it was clear that even more additions were needed in order to keep up with rapidly growing cities and agriculture in northeast Colorado. Construction on the second phase of the pipeline began in 2018 and finished in February 2020. This pipeline brings water from Carter Lake to the Boulder Reservoir Water Treatment Plant. Today, the Southern Water Supply Project pipeline carries water 110 miles from Carter Lake to cities as far south as Broomfield and east to Fort Morgan.

Carter Lake not only provides water for northern Colorado’s cities and agriculture but also generates electricity for the Poudre Valley Rural Electric Association, which is then marketed to rural customers in southern Larimer County. Northern Water’s Robert V. Trout Hydropower Plant at Carter Lake started operating in May 2012 as the district’s first hydropower project.

Recreation and Wildlife

Carter Lake provides a variety of recreational opportunities, adding to its versatility as an important resource for northern Coloradans and visitors. Larimer County Parks and Open Lands manages recreation on the lake, which includes fishing, sailing, swimming, scuba diving, and water skiing. Boating is by far the most popular activity for recreation, and visitors have access to three boat launches and a marina. The lake contains a wide variety of fish—including rainbow trout, black crappie, bluegill, and walleye—some of which Colorado Parks and Wildlife stocks yearly. Mule deer and mountain lions frequent the lakeshore, which also supports bear and elk populations.

Visitors can camp, hike, and rock climb on the more than 1,000 acres of public land that surround the lake. Nestled in rolling foothills at 5,760 feet above sea level, Carter Lake provides a beautiful location for campers, who can choose from five campgrounds and more than 150 campsites. Public outreach campaigns and a permit system reflect efforts to control the ecological impact of high visitation numbers. The visitor center helps to educate both day users and campers on how to preserve the aquatic and terrestrial ecosystems, and Larimer County Parks is able to track and limit capacity if needed.