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.
of Lake Studies
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.
Historical comparison of water quality monitoring data:
taken by Lake Kenosia Commissioner Steve Landau, September 2008
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.