Reservoir Assessments

Barr Lake and Milton Reservoir were constructed around 1909. Both reservoirs are owned by the Farmer’s Reservoir and Irrigation Company (FRICO). From 1909 to 2002, the reservoirs main purpose was to supply a reliable source of water for irrigating agricultural crops. In 2002, both reservoirs received a new use, water supply for drinking water. Over this course of 106 years, both reservoirs have received a large amount of water. Along with all that water, both reservoirs have seen their fair share sediments, debris, trash, and nutrients.

Barr Lake and Milton Reservoir were first monitored in 1975 during the first ever national lake assessment effort (National Eutrophication Study) conducted by the U.S. EPA. Only Barr Lake received any kind of attention before 1975. In 1963, Adams County Commissioners hired Ross McKinney (University of Kansas) to conduct an assessment. Mr. McKinney’s visit and study of Barr Lake’s water quality conditions provided the needed information to have a federal agency conduct their own assessment. In 1965, the predecessor to the U.S. EPA, U.S. Public Health Service, conducted a lake assessment to determine the cause and possible solutions to the odor issues that were bothering the town of Brighton, CO. Then in 2008, the BMW Association conducted a reservoir assessment of both reservoirs to begin the TMDL development process. For the past 12 years, BMW stakeholders have conducted several studies, modeled both the reservoirs and the watershed, and assisted with weekly monitoring.

Here are the reservoir assessments from over the years for both reservoirs with related reports.

Barr Lake

1965 – After 50+ years of receiving untreated and partially treated wastewater, industrial waste, and storm water, Barr Lake reached the lowest water quality moment. Hydrogen sulfide and other decaying orders would blanket Brighton which is almost 3 miles northwest of Barr Lake. From the 1965 assessment, water entering Barr Lake was void of any dissolved oxygen. The reservoir was also void of oxygen which caused the odor issues. Other water quality highlights from the study include: DO average 3.3 mg/L, Alkalinity average 274 as CaCO3 mg/L, pH average 8.1, and total phosphorus 3.35 mg/L. Because of the large amount of organic material that is loaded to Barr Lake, odor problems develop 30-60 days after the ice cover has melted. Algal blooms do occur during the summer to produce oxygen and reduce odors. Then after drawdown in the fall and the reservoir starts to refill, odor problems come back until ice cover.

U.S. Department of Health, Education, and Welfare, Public Health Services, Region 8, December 1965

1975 – U.S. EPA surveyed Barr Lake three times in 1975 along with 12 other lakes in Colorado. The survey indicated that Barr Lake was eutrophic and ranked 12th in overall trophic quality. Barr Lake did have the highest phosphorus levels out of all 13 lakes and that the reservoir was nitrogen limited for all three sampling events. Other water quality highlights from the survey include: DO average 8.6 mg/L, Alkalinity average 181 as CaCO3 mg/L, pH average 8.8, total phosphorus average 1.14 mg/L, chlorophyll-a average 28.7 µg/L, and Secchi depth average 1.2 meters.

U.S. EPA National Eutrophication Survey – Barr Lake, July 1977

2008 – AMEC (formerly Hydrosphere) evaluated water quality data from 2002 to 2005. The assessment summarized Barr Lake as hyper-eutrophic with low clarity, high nutrients, high chlorophyll-a levels, blue-green algae dominance, and DO depletion at the bottom of the reservoir. Trends did show slight improvements in phosphorus, nitrogen, and water clarity. Other water quality highlights from the assessment include: DO average 9.4 mg/L, Alkalinity average (not in report but from dataset) 155 as CaCO3 mg/L, pH average 8.8, total phosphorus average .652 mg/L, chlorophyll-a average 54 µg/L, and Secchi depth average 1.7 meters.

Barr Lake – Reservoir Water Quality Assessment (AMEC, May 2008)

2014 – Metro Wastewater Reclamation District (Metro) is a BMW stakeholder. They provide in-kind services and have conducted all of the in-reservoir monitoring since 2002. In 2014, Metro sampled Barr Lake 20 times from the deepest location near the dam. The water quality data summary includes: DO average 8.6 mg/L, Alkalinity average 124 as CaCO3 mg/L, pH average 8.4, total phosphorus average 0.282 mg/L, chlorophyll-a average 33 µg/L, and Secchi depth average 2.0 meters.

Milton Reservoir

1975 – U.S. EPA surveyed Milton Reservoir three times in 1975 along with 12 other lakes in Colorado. The survey indicated that Milton Reservoir was eutrophic and ranked 10th in overall trophic quality. Milton Reservoir was ranked 12th for phosphorus levels out of all 13 lakes and that the reservoir was nitrogen limited for all three sampling events. Other water quality highlights from the survey include: DO average 6.3 mg/L, Alkalinity average 329 as CaCO3 mg/L, pH average 8.5, total phosphorus average 0.903 mg/L, chlorophyll-a average 5.9 µg/L, and Secchi depth average 1.8 meters.

U.S. EPA National Eutrophication Survey – Milton Reservoir, July 1977

2008 – AMEC (formerly Hydrosphere) evaluated water quality data from 2002 to 2005. The assessment summarized Milton Reservoir as eutrophic – hypereutrophic with low clarity, high nutrients, high chlorophyll-a levels, blue-green algae dominance, and DO depletion at the bottom of the reservoir. Trends did show slight increase in phosphorus and pH but no changes in nitrogen, chlorophyll-a, and water clarity. Other water quality highlights from the assessment include: DO average 9.1 mg/L, Alkalinity average (not in report but from dataset) 172 as CaCO3 mg/L, pH average 8.9, total phosphorus average 0.538 mg/L, chlorophyll-a average 34 µg/L, and Secchi depth average 2.1 meters.

Milton Reservoir – Reservoir Water Quality Assessment (AMEC, May 2008)

2014 – Metro Wastewater Reclamation District (Metro) is a BMW stakeholder. They provide in-kind services and have conducted all of the in-reservoir monitoring since 2002. In 2014, Metro sampled Milton Reservoir 20 times from the deepest location near the dam. The water quality data summary includes: DO average 9.5 mg/L, Alkalinity average 156 as CaCO3 mg/L, pH average 8.8, total phosphorus average 0.399 mg/L, chlorophyll-a average 12.1 µg/L, and Secchi depth average 3.3 meters.


Overall Assessment: Barr Lake and Milton Reservoir are improving. Both Barr and Milton were some of Colorado’s most nutrient-rich reservoirs in the 1970’s and have been hyper-eutrophic for several decades due to hi nutrient and organic loads from the S. Platte River coming from wastewater effluent, industrial waste, and storm water. Since the 1960’s, both reservoirs have seen a steady improvement in phosphorus reduction. Nutrient concentrations are still high to promote blue-green algae blooms that cause problems with low clarity, hi pH, and occasional DO declines.