Where Do We Stand with Phosphorus Reductions for Lake Champlain?
January 2026 Lake Look
Lake Champlain’s health is tremendously affected by terrestrial activities. Unlike the Great Lakes, which are drained by at most four acres of land per acre of water, every acre of our lake receives runoff from approximately 19 acres of land, magnifying the effect of the adjacent countryside on water quality. Each watershed segment contributes its own pollutants, with differences in the largest sources of contaminants, whether it’s stormwater runoff and wastewater discharges from Plattsburgh and Burlington, forestry from the foothills of the Adirondacks and Green Mountains, or agricultural practices from the Missisquoi and Otter River subbasins.
Some of the most important impacts come from Montpelier – and not only when the Winooski River reaches flood stage. Those who love the lake will be watching in 2026 to see whether Vermont is on track with targeted phosphorus reductions established by the federal government in 2016, and being implemented through Vermont state programs created and funded through legislative and agency action in the state capital.
Concern about discharges to the lake, and the resulting proliferation of algae and bacteria, is not new. In 1904, the U.S. Geological Survey (USGS) investigated pollution after “persons owning property along the shores of Lake Champlain” alleged the water was being polluted. Those landowners pointed to “enormous discharges of waste materials” from wood-pulp mills in New York State as well as sewage discharges from cities on the lake, especially Burlington, causing undrinkable water, fish kills, and “luxuriant” algae growth. Marshall Leighton’s 1905 Preliminary Report on the Pollution of Lake Champlain, issued on behalf of the USGS, concluded that sewage discharges were “a growing menace” and that safeguards should be adopted to preserve the lake as a water supply. Unfortunately, it was not until 1972, with passage of the federal Clean Water Act (CWA), that the federal government required the establishment of water quality standards as well as permits for discharges into waterways.
Maintaining a focus on water quality requires ongoing action and funding. In June of 2016, the federal Environmental Protection Agency (EPA) established a Total Maximum Daily Load (TMDL) for phosphorus discharges from the Vermont portions of the Lake Champlain watershed. The TMDL sets a 20-year pollution budget, defining how much phosphorus can enter the lake between 2016 and 2036 without violating water quality standards set under the CWA. A key reason for focusing on phosphorus is an effort to curb cyanobacteria blooms. Blooms are fueled by excess nutrients—including phosphorus—and pose a significant threat to overall lake health as well as to the health of humans and pets, as blooms can release toxins and impair recreational access to the lake. Under the TMDL, Vermont must reduce phosphorus discharges from 631 metric tons per year in 2016 to 418 metric tons per year by 2036, a reduction of 213 metric tons per year.
The Vermont Clean Water Act (Act 64), passed in 2015, set regulatory standards and established the Clean Water Fund to direct state revenue to clean water projects and programs to reduce phosphorus-laden nutrient runoff. In 2019, the state determined that an annual budget of $50 million to $60 million would be needed to meet the TMDL goals. Since 2016, Vermont has issued annual progress reports, including calculating annual phosphorus reductions. The annual progress report breaks down phosphorus reductions by pollution source and by lake segment. Reductions in Burlington Bay, for example, are expected to come largely from improved stormwater management and wastewater treatment, while those in Missisquoi Bay will also include reductions from agriculture, forestry, and streams.
According to the report on 2024 reduction results issued on January 15, 2025, Vermont is making progress but needs to increase the pace of phosphorus reduction to meet the TMDL target. So far, Vermont is making just over a quarter of the annual reductions needed each year to reach the overall TMDL goal. There is still a long way to go by 2036, which is now just a decade away.
There are important questions to ask when the next annual report is released in January of 2026. Has the pace of phosphorus reductions increased, and are we growing closer to the required reductions? Is the Clean Water Budget being proposed to the legislature in line with the $50-$60 million anticipated when Act 64 was passed? Is the state funding cost-effective projects within each sector (agriculture, developed lands, forestry, streambanks, and wastewater), focusing on the areas where the largest phosphorus reductions are needed and achievable?
The large land to lake ratio of Lake Champlain’s watershed poses challenges for water quality, but also creates opportunity as the actions we take on land have a direct impact on the health of our lake. The Lake Champlain Committee’s Clean Lake Environmental Action Network (CLEAN) is a cadre of community members we can call on to speak out for the lake when opportunities for comment arise. Learn more about getting involved with CLEAN here. By watching and evaluating the state’s progress under the TMDL and advocating for phosphorus reductions, we can help ensure healthy and accessible waters for generations to come.
Lake Look is a monthly natural history column produced by the Lake Champlain Committee (LCC). Formed in 1963, LCC is a bi-state nonprofit that uses science-based advocacy, education, and collaborative action to protect and restore water quality, safeguard natural habitats, foster stewardship, and ensure recreational access. You can join, renew your membership, make a special donation, or volunteer to further our work.