Background of Lake Studies
Lake Kenosia has been extensively studied over the past 31 years:
(Please note: The terms underlined in bold are defined in the Glossary section of the website.)

In 1980, the King's Mark Environmental Review, comprised of an interdisciplinary team of 13 environmental professionals, conducted a field inspection and data review of the conditions of Lake Kenosia. They concluded that the lake is eutrophic, covered by extensive growth of aquatic plants and algae and is very susceptible for conditions leading to "accelerated eutrophication," which occurs when runoff from human development increases the rate of aging of a lake by filling the basin with nutrients and plant decay that will cause the shallow lake to fill in.

The Connecticut Agricultural Experiment Station in 1980 conducted water quality tests that supported the King's Mark conclusion that the lake is eutrophic. Field conditions in July 1980 verified the extensive growth of thick beds of watermilfoil and aquatic weeds.

In 1989 Lake Management Consultants conducted two water quality sampling rounds that included transparency (Secchi disk), plant density (chlorophyll a), and nutrients. This baseline study concluded that the lake is mesotrophic to eutrophic in character. This study also noted abundant overgrowth of the aquatic weed, Eurasian watermilfoil and moderate growths of algae. The study also determined that the bottom layer of the lake became devoid of oxygen, which causes "internal recycling" of phosphorus that is normally locked in the sediments to diffuse into the water, facilitating the growth of algae and weeds.

In 2000, ENSR Consultants conducted the most extensive keystone study of the lake. They determined that the phosphorous loading to the lake was over twice the recommended "permissible load." This is a key cause of aquatic weed overgrowth and their survey verified the excessive growth of Eurasian watermilfoil along with a similar weed, coontail. In addition to extensive chemical and biological surveys on the lake, the ENSR study also quantified that the main source of nutrients in the lake enters from runoff from the extensive urbanized watershed (as opposed to the amount of nutrients that are recycled to the lake from the sediments). They determined that a 20- 25% reduction of phosphorous loading to the lake is needed to bring the lake below the critical loading limit. Finally the study analyzed various lake management options to reverse the accelerated eutrophication of Lake Kenosia, including retrofitting storm drainage, suction harvesting, phosphorus inactivation by alum treatments and enhanced grazing of plants by introduction of weed eating fish (e.g., grass carp). Most of the management technologies are expensive.



Recent History of Lake Monitoring & Management

Lake Monitoring. The Kenosia Commission retained George Benson, a limnologist in 2005, 2007 and 2008 to monitor water quality and weed growth. In these years, Benson tested the lake water for key biological and chemical indicators. He documented dense and moderate growth of watermilfoil and coontail and blooms of green algae. Since 1999, the overgrowth of nuisance weeds has accelerated, reflecting the lack of active treatment of weeds since the 2003 ban on herbicides (see below). Additionally, the 2008 Benson report notes that the population of algae has shifted significantly to a species of blue green algae that is indicative of more rapid aging of the lake.

Herbicide treatment ban. In 2003, the Connecticut Department of Public Health ruled that application of herbicides (other than copper sulfate for algae) would be prohibited in Lake Kenosia due to the fact that the City sporadically uses the lake as an emergency water supply. The City had routinely conducted herbicide treatments with SONAR throughout the 1990s, which controlled the growth of nuisance weeds, particularly watermilfoil. This herbicide ban terminated this weed control strategy.

Lake Kenosia Commission goals. In 2006, the Lake Kenosia Commission re-defined its goals for managing the lake, focusing on weed management, and demonstration projects and public education. Monitoring will continue, and efforts to control the weeds will focus on watershed demonstration projects such as the buffer gardens at the Lake Kenosia Park, a feasibility study for introducing grass carp and grants to conduct projects to show how small steps can improve the quality of Lake Kenosia.

The buffer gardens at the Lake Kenosia Park. The buffer gardens are a demonstration project to bring beauty to the shoreline of the lake, promote biological diversity, improve water quality, and deter Canada Geese. They also preserve sand from the erosive effects of stormwater. For more detail link to the buffer gardens section of the website. The focus of this project is discussed below.

In 2011, Lake Kenosia is characterized by "co-dominance" of the lake waters with some areas that were covered almost exclusively with watermilfoil (north -north east side, from the Lake Kenosia Park to the lake outlet at Kenosia Avenue) with the remainder of the shallow zone of the lake that has cover of dense growth of both coontail and milfoil. One significant exception to the dense shallow water dominance of these weeds is the park beach - which was relatively clear of weeds, following several years of suction harvesting. This project will be discussed in more detail, below.

In addition to Eurasian watermilfoil and coontail, which are rooted and grow to the surface of the water column, Lake Kenosia is also characterized by an assemblage of emergent aquatic plants - rooted in the sediments, growing through the water column and with leaves that emerge over the surface of the water. This includes water lilies and pickerelweed. These plants are not considered nuisances (do not interfere with recreation), do not massively overgrow the shallow water zone and provide a balanced ecological function for the lake (including cover areas for fish populations).

Finally, there is the growth of algae - microscopic plants and cyanobacteria that grow directly on surface water and do not have stems. Although they are individually microscopic, they grow colonially - joining into clumps or mats that float on the surface of the lake. Unlike the rooted weeds, which draw their nutrients from the lake sediments, algae are entirely dependent upon the nutrients that are in the water column. They are, therefore, more direct indications of the eutrophication (aging) status of a lake. The algae that are present in Lake Kenosia are indicative of an aging lake. This was noted in the 2000 ENSR Diagnostic Study and has been echoed by the Benson Environmental surveys of recent years. In the 2008 Benson survey, the report noted: the shifting trend from dominance of chrysophyte algae in the 1980s to blue-green algae noted in the 2008 Benson Environmental survey, and a notable increase in the density of algae colonies in the water. "Blooms" of algae can sometimes occur in Kenosia (as was documented by Benson in 2007) but algae growth in Lake Kenosia is still considered moderate for a recreational lake. The lack of a nuisance infestation of algae in Lake Kenosia is likely, due to the overgrowth of the rooted weeds, which are currently utilizing the vast reservoir of nutrients available for plant growth. However, successful control of the nuisance weeds that dominate the lake may result in increased periods of nuisance algal blooms in the lake. From a lake management perspective, this potential side effect" can be effectively controlled by application of copper herbicides that are still allowed for treatment in Lake Kenosia.
 
All of this characterization of the current state of Lake Kenosia leads to the point of lake management measures and the role of the community in improving water quality, shoreline and lake habitat and recreational quality of the lake. The Lake Kenosia Commission is Danbury's advocate and watchdog for stewardship and lake management. Over the past several years, the Kenosia Commission has investigated several management techniques for the lake and has invested in pilot projects to improve the quality of the lake's environment. Notable in these efforts are the following successes:

1. Pilot projects to evaluate non-chemical control of nuisance weeds, including hydroraking, benthic covers and suction harvesting. The most promising non-chemical alternative is suction harvesting. In 2008, the suction harvesting of the waters off the beach at Lake Kenosia Park (an area approximately 15,000 square feet) effectively maintained the bathing area at the park clear of nuisance weeds. This was documented by a pretreatment and post treatment snorkel survey by Kozuchowski Environmental Consulting and was independently cited by Benson Environmental Inc., in his 2008 lake-wide survey. The report of Benson Environmental observed that the park's bathing area was the "weed free" exception to the coverage of all other areas of the lake by moderate-dense coverage of coontail and milfoil. According to the suction harvesting contractor (Lockhart Environmental), a bathing area like the one at Lake Kenosia Park could benefit from a few repeated years of harvesting, along with an oil containment boom (cleared daily of weed cuttings drifting in from other parts of the lake) to maintain the "oasis" condition of allowing the public to attain a weed free zone for swimming. Another three years of suction harvesting and evaluations of the performance took place to verify that this technique could be the non-chemical weed treatment of choice. If the continued success of this operation is verified, shoreline landowners including homeowners, the banquet hall, condominium owners, and the State boat launch may replicate the operation, to create additional "oases" of treatment.

In addition, the Commission evaluated grass carp introduction as a means of grazing control of bottom weeds. However, the potential negative effects of backwater flooding due to clogging of the outlet structure at the Kenosia Avenue culvert, the possibility of inducing algal blooms and the unlikely prospect of the Connecticut DEEP permitting this work has removed this strategy from active consideration.

Finally, The Kenosia Commission has noted the documented success of the seeding of lakes in the Midwest with the milfoil weevil, which has recently been employed at Candlewood Lake. This would be a gradual long-term removal process that would selectively eradicate milfoil plants, whose stems would be destroyed by the weevil. The milfoil weevil is a native species and feeds exclusively on Eurasian watermilfoil. The selective and gradual removal of milfoil would allow a gradual re-colonization with plants that are less of nuisance weeds and may promote a better ecological diversity of plant life in the lake. Though it is currently too expensive to employ this method of control in Lake Kenosia at this time, we will continue to monitor usage of the weevil and its results.

2. The Buffer Gardens. The State of Lake Kenosia is earmarked, in 2011, by a great success in the City of Danbury's buffer gardens demonstration project (see photo of buffer garden iat the beginning part of this report). Launched in 2006, the project utilized a Meserve Grant and collaboration with The Land Trust of Danbury to establish a small plot of grasses, shrubs and flowering plants that created a microhabitat, an environmentally attractive garden that flowers sequentially throughout the growing season. In 2007 and 2008, the initial plot was extended to cover an area that circumscribes approximately 20% of the beach area in the Lake Kenosia Park. In 2011, after the installation of Phase 3, the buffer gardens completely encircled the shoreline of the park and the beach. The gardens have been successful in dispersing Canada Geese - eliminating the water quality problems due to beach pollution with their feces - away from the park. They also provide a filtering mechanism for intercepting stormwater flow to the lake and filtering out nitrogen, phosphorous and other pollutants. In addition to these benefits, the buffer gardens have been shown to offer a surprising advantage in "holding" the beach from erosion after major storm events.