The State of Lake Kenosia 2013
A non technical summary of current environmental conditions in Lake Kenosia

The photo below illustrates the water and shoreline of Lake Kenosia with one of the buffer gardens (discussed in more detail, below) This report aims at condensing an extensive series of lake studies, lake management strategies and the current focus of the Lake Kenosia Commission in conserving Lake Kenosia, in a non-technical format. The goal of this report is to provide citizens of Danbury with a "snapshot" of the current water quality of the lake and the challenges that are being addressed by the Lake Kenosia Commission, in creating environmentally desirable conditions for recreation and natural beauty.

This annual report includes the same summary (from previous annual reports) of past studies of the lake and management options that have been completed over the past 30-plus years. A listing of significant recent events that will affect the quality of the lake follows this. The "State of the Lake" report concludes with a discussion of the challenges facing the community in managing the lake and the best management strategies that are being pursued by the Lake Kenosia Commission.


 

 

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.

 

Discussion

The State of Lake Kenosia, simply put, is aging fast. The scientific term for the aging of a lake is eutrophication. When a lake is aging fast, it is referred as "cultural eutrophication." The evolution (or aging) of a lake from a deep-water body to a marsh is a natural process that is fueled by nutrient inputs from the watershed and the bottom sediments of the lake to the water body. These nutrient inputs (particularly phosphorus) fertilize the waters to allow the growth of algae and weeds.
The extensive studies of Lake Kenosia that are described here all document the extensive fertilization of the lake that has fueled the growth of nuisance weeds (watermilfoil and coontail) and algae. The sources of fertilization in Lake Kenosia are:

Runoff of nutrients from the watershed - Roads and parking lots accelerate the flushing of nutrients that would otherwise be absorbed by soil and vegetation. The watershed land area that drains to the basin of Lake Kenosia is very large compared to the area of the lake. Also, human development in the watershed since Interstate 84 was constructed has transformed open space areas to housing and commercial development. Both of these factors result in a large influx of nutrients to the lake from the land area that drains into it.

Recycling of nutrients from the bottom sediments - The bottom muds of the lake are a reservoir of decaying plant materials that include the nitrogen and phosphorous nutrients that were locked in their tissues. Every summer there is a release of these nutrients back into the lake water that "recycles" them into the water column making them available for new plant growth.

As a result of both sources of nutrients, Lake Kenosia is aging faster than it would have if human development in the watershed had not occurred as rapidly as it did in the last 50 years. The biggest manifestation of the human based nutrient flow to the lake is an overgrowth of rooted aquatic weeds, primarily coontail and Eurasian watermilfoil in the shallow water zone of the lake. Coontail is a native plant that grows naturally in North America. Eurasian watermilfoil is a plant that does not normally grow in North America, but was imported from Europe and has proliferated throughout many lakes in the US. Both are nuisance weeds, which interfere with recreational uses of swimming and boating. However, of the two weed species, coontail is ecologically more acceptable since it is part of the normal habitat of this part of the country and better suits its ecological role in Lake Kenosia. However, the large nutrient input to Lake Kenosia makes the overgrowth of these weeds a problem. The two species are "cousins" - anatomically and physiologically similar. Hence, the pattern of growth of these weeds in Lake Kenosia see-saws from year to year. For example, prior to 1989, watermilfoil dominated the lake. Then from the late 1990s to 2004, coontail was the dominant weed in Lake Kenosia, with only small pocket of milfoil. This may be attributed to a period of time when the lake was routinely treated with contact herbicides that had a greater effect of controlling watermilfoil until the 2003 ban of herbicide applications to Kenosia.

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 characterized in 2013, 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 discouraging 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.

Historical comparison of water quality monitoring data:

In 2013, following the September 2012 monitoring of the Lake, the Lake Kenosia Commission conducted a historical comparison of the data collected from 1980 -2012. A graphical presentation of this data and a detailed discussion of the water quality parameters tested and the interpretation of the results can be found in the Water Quality Monitoring section of this website. Overall, the data for each parameter is too sporadic (5 samplings over 30 years) and the database is too small to draw conclusions about emerging trends at this time. However, the long period of monitoring provides a good baseline to compare to future monitoring periods. In this regard, the Lake Kenosia Commission has committed to monitoring the Lake at least once per year to create a database that will be long enough and frequent enough to establish trends. Five to ten years of monitoring results should allow the Lake Kenosia Commission to begin drawing conclusions whether the lake is

 
 
Photographs taken by Lake Kenosia Commissioner Steve Landau, September 2008

The photo on the left, illustrates the extreme erosive force of a severe storm that occurred in 2008 in the center of the beach area. The photo below exhibits the area immediately below the initial planting of the buffer garden after the same storm, exhibiting only minor erosion and a minimal loss of beach sand, demonstrating yet another benefit of the buffer gardens: financial. The September 2008 storm that caused the erosion was not a hurricane or an extreme event. Typically a storm such as this occurs a few times every year. Hence, the now-completed buffer gardens will, over time, save the City the cost of replacement sand for the beach.
 

 
 

 
Summary 

In summary, there are a host of options for controlling weeds and beautifying Lake Kenosia. First of all, there are the expensive options that include in-lake alum feed systems or massive watershed stormwater control projects. These control methodologies are the most effective and time efficient methods for reducing nutrient inputs that would ultimately eliminate the massive weed growth that currently plagues the Lake. However these systems will be in the range of $1,000,000 to $ 5,000,000 and in this economic climate are not realistic options at this time. However, these aggressive in-lake or watershed-based treatment technologies should be considered the gold bar standard for the City of Danbury and the Lake Kenosia Commission to strive for in future years, when grants and/or Foundation funding becomes more available for such projects.

Short of aggressive nutrient removal systems, the options are limited to short term weed controls. In 2010, the Commission prepared the table below that identifies short term weed control options. In 2010, the Lake Kenosia Commission selected suction harvesting as the weed control option, but which would be limited to the Lake Kenosia Park Beach. Suction Harvesting was deployed in 2010, 2011 and 2012, which took place in June of those years. The suction harvesting successfully removed weeds from the bathing area in a manner that allowed a weed-free bathing zone from the beach to the dock. The success of the weed control was verified by a late season "snorkle survey" in late August or early September.