Lake Water Quality Management

Water Quality Concerns

Eutrophication - Eutrophication is a form of water pollution caused by excessive enrichment with plant nutrients, organic matter, and sediments. These pollutants are often called non-point source pollution because they emanate from diffuse sources.

Symptoms of eutrophication include:

  • dense algae blooms,
  • nuisance weed beds, and
  • depletion of oxygen in bottom waters.
These conditions:
  • limit recreation opportunities,
  • reduce the economical value of property, and
  • diminish the ecological integrity of lakes.
Often the source of non-point pollution causing eutrophication is generated from the land that drains to the lake. This land area is known as the drainage basin and is also called the watershed. Generally most programs to abate lake eutrophication require watershed management to reduce pollutants in stormwater runoff.

Non-native Invasive Plants - Many of Connecticut’s lakes and ponds experience nuisance growths of aquatic plants that can interfere with swimming and boating. Eurasian water milfoil, variable water milfoil, and fanwort (Cabomba) are three non-native invasive plant species that have become nuisance plants over the past 25 years. These three plants grow rapidly early in the spring, overtopping and shading native plants. Unlike native plants, they also exhibit the tendency to grow to the surface of the lake and spread horizontally, covering the surface with tangled mats. Unfortunately, eradication of these invasive plants is usually not feasible and the objectives of most control programs are to contain spreading and to minimize impacts to recreation.

Control methods being used in Connecticut include:

  • harvesting,
  • herbicide treatments,
  • sediment dredging,
  • winter drawdown,
  • sterile grass, and
  • bottom barriers.
Experimental control methods being investigated include aquatic weevils and combinations of aquatic herbicides.

Components of Lake Water Quality Management

Baseline Monitoring - Synoptic water quality monitoring is conducted to assess the extent of eutrophication. Over time, baseline monitoring is repeated to evaluate trends in water quality conditions.

Diagnostic Study - Intensive water quality monitoring is conducted, typically over the course of a year, to characterize water quality conditions and to identify specific water quality problems that need attention.

Watershed Assessment - A detailed evaluation of important watershed features, such as land uses and soil types, is conducted to identify active or potential sources of pollution that need to be addressed to protect and improve lake water quality.

Management Plan - The results of the diagnostic study and watershed assessment are used to evaluate alternative methods to remediate undesirable lake conditions and to manage pollution sources in the lake watershed. The plan identifies the most cost effective ways to achieve water quality objectives.

Implementation - Remediation of undesirable lake conditions may involve one or more of a variety of technologies including sediment dredging, weed harvesting, artificial aeration, and aquatic herbicide treatments. Watershed management invariably involves the implementation of best management practices for non-point sources of pollution. Examples are improved lawn fertilization practices, routine catch basin cleanouts, and installation of stormwater treatment technology. For river impoundments, watershed management may also involve upgrading treatment for point source wastewater discharges.

Public Education and Technical Assistance

The development of a successful lake management program is dependent on active community participation. 

Assistance for Aquatic Plant Management

Several state programs work together to provide technical and financial assistance to lake communities for aquatic plant management.  

  • The Bureau of Materials Management and Compliance Assurance is responsible for technical assistance and permitting related to aquatic herbicide and algaecide treatments.
  • The Bureau of Natural Resources' Inland Fisheries Division provides technical assistance on aquatic resources and administers the permitting of triploid (sterile) grass carp as an aquatic vegetation control tool in lakes and ponds.
  • The Bureau of Natural Resources' Division of Wildlife, Natural History Survey collects information on aquatic plant communities and the distribution of species of concern.
  • The Connecticut Agricultural Experiment Station conducts applied research on scientific questions related to aquatic plant control.

Funding Sources

Limited federal funding for projects in lake watersheds is available from Section 319 of the Federal Clean Water Act. This program usually requires a 40% match and applications are competitively ranked.  Lake management projects have also been funded in part or entirely with local funds.

Technical Assistance for Pond Owners

Ponds often exhibit vegetation and algae growth within a relatively short time after being constructed. Management of a pond to control the growth of unwanted vegetation may include dredging, herbicide treatments, weed harvesting, or some other technique that eithers kills, removes, or prevents the vegetation from growing. Site conditions and available funding should be considered when determining which technique to employ.

Caring for Our Lakes (PDF)

The booklet "Caring for Our Lakes", originally published in 1994, provides an overview of watershed and in-lake management methods. Some of these methods can be used by local individuals, businesses, lake associations, town officials, and other interested parties. Other tasks may require the services of professional experts such as limnologists, environmental engineers, or resource managers.
NOTE: Though most of the information in the booklet is pertinent today, it has not been updated to reflect regulatory and programmatic changes that have occurred since 1994.

Dam Safety Program

Watershed Management

Content last updated October 9, 2019.