Southern Water Supply Project

The First Phase of the Pipeline

The Southern Water Supply Project pipeline carries Windy Gap Project and Colorado-Big Thompson Project water 110 miles from Carter Lake to several Northeastern Colorado communities. Plans for year-round deliveries through the pipeline began in 1991.

Alternate Supply for Broomfield

In the early 1990s Broomfield received half its water from Great Western Reservoir, located downstream of Rocky Flats, a former nuclear weapons facility. Due to potential contamination of the reservoir, the U.S. Department of Energy agreed to provide Broomfield with an alternate water supply. At that same time a regional study forecasted an increasing demand for water in the southern portion of Northern Water's service area. Communities facing higher water quality standards needed reliable year-round water deliveries. 

The proposed Southern Water Supply Pipeline met Broomfield's needs and provided other communities with a year-round water supply. In addition, sharing a single pipeline was less costly than if each participant built its own project.

Southern Water Supply Project construction.
Construction of the Southern Water Supply Pipeline.
Pipeline Construction 

Construction on the first phase of the pipeline, from Carter Lake to Broomfield, began in 1993. The last 41-mile section from Platteville to Morgan County was finished in 1999. Total project construction costs were $68 million. 

Due to project participants' increasing water demands, particularly during the higher-demand summer months, a West Longmont pump station was added in 2003. An additional pump station at Broomfield followed two years later and then the Eastern Pump Plant on the pipeline’s eastern section in 2022. Together, the three pump stations increased system capacity by 80 percent.

Project Participants 

While we own and operate the Southern Water Supply Project pipeline, individual participants have contractual rights to the water and pay their proportionate shares of operations, maintenance and replacement costs of the project. The project is owned, operated and maintained on behalf of the participants by the Southern Water Supply Project Water Activity Enterprise, Northern Water. The project participants are: Fort Morgan, City and County of Broomfield, Hudson, Berthoud, Longmont, Erie, Louisville, Morgan County Quality Water District, Little Thompson Water District, Central Weld County Water District and Superior.

Southern Water Supply Project Map

Southern Water Supply Project II

With continued Front Range growth, Boulder, Left Hand Water District, Berthoud and Longs Peak Water District agreed to fund a second phase of the Southern Water Supply Project for secure, year-round water deliveries. These entities previously depended in part on seasonally operated open canals for water deliveries, which at times are subject to water quality concerns. 

Construction on phase two of the pipeline began in 2018 and was completed in early 2020, with construction costs totaling approximately $38 million. Total project costs, including design, permitting, administration, management and right-of-way were approximately $44 million. 

The Southern Water Supply Pipeline II traverses from Carter Lake south to the Boulder Reservoir Water Treatment Plant, a total distance of 20 miles. The first 12 miles parallel the first Southern Water Supply Project pipeline (constructed in 1995) from Carter Lake to St. Vrain Road near Longmont’s Vance Brand Municipal Airport. The pipeline’s last 8 miles deliver water to Left Hand Water District and the Boulder Reservoir Water Treatment Plant. 

Last underground pipe being placed on SWSP
Crews lay the last pipe on the Southern Water Supply Pipeline in February 2020.