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Esther Vincent Water Quality Manager (970) 622-2356

As new water quality challenges surface, Northern Water develops new monitoring programs and conducts studies to target specific areas of concern or interest and then develops strategies to protect or improve water quality where needed.

VISIT OUR WEBSITE For data, reports and program descriptions visit and click on “Water Quality” Water Quality Program


The backbone of the Water Quality Program is the Baseline Monitoring Program, which started in 1991. In response to these developing needs, Northern Water has continuously expanded its water quality-related activities over the past 20 years. The C-BT and Windy Gap projects are major drinking water supply sources for most of the municipalities they serve, so protection of the projects’ watersheds continues to be a concern as drinking water treatment requirements change.

Water Quality Program

This trend parallels an increased public awareness of water quality and environmental issues and a strengthening of the regulatory framework at the federal and state levels. s the Northern Front Range population continues to soar, ownership of C-BT Project water allotment contracts increasingly shifts from agricultural to municipal and industrial water users.


Why Water Quality Matters

Between April and October, the primary growing season, Northern Water also delivers water to more than 120 ditch, reservoir and irrigation companies serving thousands of farms and more than 640,000 acres.

Measuring parameters with a probe

About 860,000 people live within Northern Water boundaries, which encompass 1.6 million acres in portions of eight counties: Boulder, Broomfield, Larimer, Logan, Morgan, Sedgwick, Washington and Weld. orthern Water is a public agency created in 1937 to contract with the federal government to build the Colorado-Big Thompson Project, which collects water west of the Continental Divide and delivers it to Northeastern Colorado. Northern Water and the U.S. Bureau of Reclamation jointly operate and maintain the project.


Water Quality Program


About Northern Water Three Lakes Water Quality


he Three Lakes – Lake Granby, Shadow Mountain Reservoir and Grand Lake – are part of the Colorado-Big Thompson Project’s water collection system in the Upper Colorado River basin.

Studies and reports A two-year study in cooperation with the University of Colorado Center for Limnology is examining factors affecting clarity in Shadow Mountain and Grand Lake. Northern Water and Reclamation along with Grand County are compiling annual reports summarizing Three Lakes water quality and operations.

COLLABORATORS The Three Lakes Technical Committee of state and federal representatives and local stakeholders formed in 2008 to study nutrient loading, but its responsibilities have now expanded to water quality issues, including Grand Lake clarity.

Wintertime sampling

ISSUES Studies have identified issues to investigate, including: Algae blooms in Shadow Mountain and Grand Lake Aquatic vegetation in Shadow Mountain Grand Lake (left) and Shadow Mountain Reservoir

Dissolved oxygen in Shadow Mountain Effects of algal productivity on aquatic life

Development of alternatives Northern Water and Reclamation are committed to assessing Grand Lake’s water quality and clarity and implementing reasonable mitigation. Reclamation has identified alternatives to study.

Horsetooth Water Quality Study Horsetooth Reservoir is part of the C-BT Project and stores water for delivery to Northeastern Colorado water users. Reservoir water goes directly into plants for the TriDistricts, Fort Collins and Greeley.

Ability to meet future nutrient standards Algal toxins Grand Lake water quality, including clarity Taste and odor for Grand Lake’s direct water intakes Quality of water released to the Colorado River Quality of water diverted to the East Slope Lake Granby

Three Lakes water quality has become a focus based on recent events, including: A severe algae bloom in Grand Lake in 2007, due to nutrient inputs related to a Shadow Mountain drawdown. Findings in 2008 demonstrating a need to investigate nutrient loading and nutrient sources into the Three Lakes. The Colorado Water Quality Control Commission’s adoption of a numerical clarity standard for Grand Lake to be implemented in 2015 unless a more appropriate standard can be established; data shows the proposed standard cannot be met. The commission’s 2012 adoption of nutrient criteria to become effective in the Three Lakes in 2015.

ACTION Monitoring Monitoring is critical for understanding water quality. The following programs support water quality studies and monitor for: Baseline water quality Algae toxins Shadow Mountain dissolved oxygen Clarity Specific conductivity and water temperature Real time conditions in Shadow Mountain’s channel and Granby’s pump canal Water quality model The Three Lakes water quality model is an essential resource used to better understand water quality dynamics and to evaluate alternatives for improvement.

Horsetooth Reservoir

Horsetooth Reservoir’s water quality has been monitored for more than 20 years, and Northern Water and stakeholders have been working to understand the causes of reservoir water quality issues related to aquatic life and drinking water treatment. A water quality model was developed in 2012 and serves as a tool for understanding causes of low dissolved oxygen concentrations and to investigate water quality impacts of changes in the watershed and in C-BT operations. More information on the model is available at

Water Quality Monitoring Programs Baseline Monitoring Program

Emerging Contaminants


he monitoring sites in the Baseline Monitoring Program cover both the Colorado-Big Thompson and Windy Gap projects throughout eight watersheds. Monitoring frequency varies from monthly to weekly depending on site location. The program focuses on nutrients, metals, general chemistry, phytoplankton and zooplankton. The program is used to monitor spatial and temporal trends in C-BT and Windy Gap water quality as well as the potential impacts of releasing C-BT and Windy Gap water into rivers and streams. All release points are monitored for compliance with state water quality standards. Staff members from the U.S. Geological Survey conduct some of the sampling, and members of Northern Water’s field services department conduct the rest, utilizing USGS protocols modified for Northern Water’s needs.

Algae Toxins

Northern Water participates in a collaborative program spearheaded by Grand County to monitor for algae toxins in the Three Lakes system, which includes Grand Lake, Shadow Mountain Reservoir and Lake Granby. The Grand County Water Information Network, a nonprofit organization that manages and coordinates water quality monitoring, information and educational programs, collects the program’s samples weekly from July 1 to September 15 at nine sites in the C-BT Project’s West Slope Collection System: Grand Lake, Shadow Mountain Reservoir, Lake Granby, Willow Creek Reservoir and Windy Gap Reservoir. The data supports Grand County’s Emergency Response Plan in the event toxins would be released into the water bodies during an algae bloom.

Syntex Hazardous Waste Landfill The former Syntex Landfill near the St. Vrain Supply Canal was used by pharmaceutical manufacturers during the 1960s and 1970s as a hazardous waste disposal site. It was cleaned up in the 1980s but hazardous materials remain. Northern Water installed monitoring wells to detect any hazardous materials that could reach the canal. The program monitors and samples four monitoring wells along the canal for total dissolved solids, chloride, tetrahydrofuran, ethyl ether (diethylether), pH, specific conductivity and temperature. Ongoing monitoring every three to five years since the 1980s has shown no sign the hazardous materials are migrating toward the canal.

Buoy system near Shadow Mountain Dam

Shadow Mountain Dissolved Oxygen

Northern Water initiated dissolved oxygen monitoring in Shadow Mountain Reservoir in 2008 to determine the causes, extent and duration of low dissolved oxygen events in the reservoir during late summer. Dissolved oxygen helps protect the aesthetic qualities of water and maintain aquatic life, and dissolved oxygen concentrations are a gauge of water quality. Monitoring includes a buoy system near the reservoir’s dam that collects dissolved oxygen data every four hours, as well as collection of hourly data on the Granby Pump Canal, a source of low dissolved oxygen to the reservoir. Monitoring will provide a baseline of data to evaluate the effectiveness of future mitigation strategies.

The South Platte Specific Conductivity Monitoring Program records continuous specific conductivity concentrations using more than 20 automated stations to provide a baseline of data. The stations are on the Lower South Platte River and its tributaries: the Cache la Poudre, Big Thompson, Little Thompson, and St. Vrain rivers as well as Boulder Creek.

Specific Conductivity and Water Temperature in the Three Lakes

Specific conductivity and water temperature are continuously monitored at 10 inflow sites to the Three Lakes in order to inform existing and future water quality modeling efforts. Specific conductivity is often used to study circulation patterns and hydrodynamics in water bodies.

Macroinvertebrate assemblages are often sensitive to a wide range of environmental disturbances and pollution. Biological monitoring, or biomonitoring, evaluates aquatic environments, and it has important advantages over physical or chemical water quality monitoring. Sustained biological monitoring studies help explain the effects of long-term influences such as population growth, urban development and land use changes. The biomonitoring study evaluates the biological and ecological integrity of streams potentially influenced by Northern Water activities.

Water Temperature

This program provides real-time data on directional flow between Grand Lake and Shadow Mountain Reservoir with the use of an Acoustic Doppler Velocity Meter (ADVM) and real-time water quality data in the connecting channel for chlorophyll, turbidity, specific conductivity and pH. The data are used to inform future and existing water quality modeling efforts. The program is maintained by the USGS and funded by Grand County, the Colorado River Water Conservation District, Northern Water and Reclamation.

The program monitors water temperature for protection of aquatic life and for compliance to state water quality standards downstream of reservoirs, in canals at points of release to the streams, and in streams above and below release points. There are more than 30 monitoring sites in the Colorado River between Lake Granby and Kremmling, and several more sites on each of the South Platte River tributaries on Colorado’s East Slope at points of release of C-BT and Windy Gap water into the streams.

Clarity in Grand Lake and Shadow Mountain

Algae Control Program Monitoring Northern Water uses approved herbicides or other agents in East Slope canals in order to control algae growth. Algae can restrict canal capacity and pose operations and maintenance difficulties. Northern Water’s algae control monitoring efforts are in place to ensure that herbicide applications in canals are in accordance with labels and water quality regulations and to monitor the efficiency of treatments.

In 2008 the Colorado Water Quality Control Commission adopted a clarity standard for Grand Lake. The Grand County Water Information Network and volunteers collect Secchi data weekly between June and October, and then three times a week during periods of modified C-BT operations in Grand Lake and Shadow Mountain Reservoir. These Secchi data provide a baseline of data to support an official review of the Grand Lake clarity standard in 2014, which will become effective in 2015. Data collection also helps monitor clarity changes related to the operations of C-BT Project facilities.

Flowing Reservoir Non C-BT Canal C-BT Pipeline/Canal Pipeline River Tunnel Continental Divide

Lake Granby

Specific Conductivity in the Lower South Platte


Shadow Mountain Connecting Channel


St. Vrain Supply Canal south of the former Syntex Landfill

Emerging contaminants are a growing concern to human health and the environment, and in 2009 Northern Water launched a collaborative monitoring program. University of Colorado research scientists Imma Ferrer and Michael Thurman helped design the program and provide expertise on new research and developments regarding emerging contaminants. The program monitors more than 150 contaminants, including pesticides, herbicides, pharmaceuticals, personal care products and endocrine-disrupting compounds. Monitoring site locations include Windy Gap Reservoir, the Adams Tunnel, Carter Lake, Horsetooth Reservoir, Boulder Reservoir and the Cache la Poudre River.

Baseline Water Quality Monitoring Sites

Horsetooth Reservoir

WQP Water Quality Program

Estes Park OLY Lake Estes AT-EP


Mary’s Lake

Adam’s Tunnel

Windy Gap CR-WGD Reservoir WG-DAM FR-WGU


CR-WGU Granby






Carter Lake



Flatiron Reservoir

Pinewood Reservoir









Fort Collins HT-SOL


West Slope Sites



Horsetooth Reservoir


East Slope Sites

Northern Water Water Quality Program  
Northern Water Water Quality Program