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Water and Watershed Committee
Mission: Monitor, protect, and restore water quality to preserve ecological
    integrity and enhance recreational value to LHA members
Members: Bill Powell
  Dave Hall
As members of Lake Harwinton Association, we all share the same goal of maintaining and improving the water quality of our lake. Lakes are very complex ecosystems, and the solutions to water quality problems are neither simple nor easy. There is an enormous amount of information on lake ecology and management on the web.  Some is excellent, some is good, and some (typically from people who are selling something) is just plain misleading.

We have put together links to documents and websites that we believe are informative and accurate, located here: Reference Material, Articles, and Links.  This list is a work in progress, so check it every so often to find current information. There are many terms in lake management which may be unfamiliar to you. A basic glossary of terms is located here: Glossary

Here is a running chart showing weekly measurements of water clarity, an indicator of quality: Secchi Chart 2024

The purpose of the Water Committee webpage is to help you understand how our lake works, how it is managed, and how you can make a positive impact on our lake's water quality.  We have pulled together information from many sources to provide a summary, organized into the sections listed below.  If you want to jump right to one of the sections, just click on it below.

What is a Lake?

How Does a Lake Work?

What Can Go Wrong?

What Can Be Done?

What YOU Can Do



WHAT IS A LAKE?                      

A lake is a deep basin that holds water for an extended period of time.  It is an ecosystem, a community of interaction among animals, plants, microorganisms, and the physical and chemical environment in which they live.  Critical to any lake ecosystem is the lake's watershed, the surrounding land area that drains into the lake.

Lake Harwinton is an artificial lake of 41 acres in area, created over 70 years ago.  Our basin can be divided into two parts: a northeastern arm consisting of mostly shallow water (5 to 6 feet), and a southwestern bay where water depths mostly exceed 10 feet and where the deepest water depths of 21 feet are located.  Water flows into the our lake’s basin via inlet  streams, surface inputs like rain and melting snow, and springs connected to groundwater that is held in the soil or aquifers. Water flows out of our lake over a spillway, which controls the maximum height of the water.

A watershed can best be described as a funnel, and includes all land, run-off, and streams which topographically slope and drain into a lake.  As water flows toward the lake, the watershed does two things:  (1) it carries soil, chemicals, nutrients and other materials with it, and (2) it filters the water with vegetative borders or manmade means.  Both affect the health of the lake.  The Lake Harwinton watershed is 429 acres (including 145 acres outside of the LHA) of mostly upland forest and wetlands, with high density single family residential housing around the lake.  For more information, refer to the 2014 NEAR Watershed Evaluation.

The water cycle consists of processes by which water circulates between the earth's water bodies, atmosphere, and land, involving precipitation as rain and snow, drainage in streams and rivers, and return to the atmosphere by evaporation and transpiration: 

The Water Cycle



Lakes Form Layers and "Stratify".  Lakes in our climate tend to stratify to form layers, especially during summer. This happens because the density of water changes as its temperature changes.  Water is most dense at 39°F. Both above and below that temperature, water expands and becomes less dense.

Summer stratification occurs when the surface water becomes less dense as it warms, separating it from colder, denser, bottom water.  The lake stratifies into three distinct thermal layers:

Image Source: Kentucky Department of Fish and Wildlife

The top layer (epilimnion) is the warmest and lightest layer of water. It is roughly equivalent to the zone of light penetration, where most weeds and algae grow.  Wind action and photosynthesis continually supply oxygen to this layer. 

The middle layer (thermocline) is a transition zone in which the temperature declines rapidly, and light penetration ends. The thermocline is a narrow band of transition which helps to prevent mixing between the layers.  The thermocline at Lake Harwinton is at a depth of about 10 feet.

The bottom layer (hypolimnion) contains the coldest, densest water.  Removal of dissolved oxygen occurs in this layer as a result of the decay of organic material, such as algae and weeds that have died and settled on the bottom. This oxygen cannot be replaced from the atmosphere in the summer when a lake is thermally stratified. Fish habitat is then lost and only organisms that can tolerate anaerobic, or oxygen-free, conditions live in the hypolimnion. If all oxygen is removed, phosphorus and ammonia nitrogen from the sediments are released into the upper layers. These nutrients can reach the epilimnion and stimulate an algae bloom if wind mixes the water or during fall turnover.

Fall turnover occurs in the late summer or fall when the epilimnion (top layer) cools, thereby becoming denser, and the lake mixes from top to bottom.  During the fall turnover, the temperature and nutrient levels become uniformly mixed throughout the water column and dissolved oxygen is replenished in the water column.

Winter stratification occurs after the fall turnover, where the coldest waters are fond at the bottom.

Spring turnover: Just before the ice melts, the water near the bottom will be at 39°F. Water above that will be cooler, approaching 32°F just under the ice. As the weather warms, the ice melts and the surface waters begin to heat up. Wind action and increasing density cause this surface water to sink and mix with the deeper water.  The lake remains physically and chemically uniform until the surface begins to warm with the onset of summer stratification.

The seasonal cycle of fall and spring turnover is very important to mixing of nutrients, variability in oxygen in the deeper waters, and the types of organisms that live in our lake.  The cycle is illustrated below:

Lakes Flush.  The average time required to completely renew a lake’s water volume is called the hydraulic flushing rate.  In an average year, "hydraulic flushing" takes place in Lake Harwinton every 170 days, or 2.2 times per year. The flushing rate of a lake will determine how it responds to many inputs from the atmosphere and the watershed.

Lakes Have Zones of Biological Communities: A lake can be divided into zones, or communities, of plants and animals. Extending from the shoreline is the littoral zone, where aquatic plants are dominant. These plants play an important role in the overall aquatic community by producing oxygen and providing food and shelter for insects, crustaceans, frogs, turtles and fish. The area of open water is the limnetic zone. This area extends down to the point where light no longer penetrates, and is the habitat of phytoplankton (algae), zooplankton (microscopic animals), and fish. The phytoplankton are very important, serving as the base of the lake's food chain and producing oxygen.

The process by which green plants (including algae) produce oxygen from sunlight, water and carbon dioxide is photosynthesis. A pigment produced by the plants, chlorophyll, speeds this process. Since sunlight is very important to photosynthesis, oxygen will be produced only as deep as the sunlight penetrates. The depth of light penetration (the approximate depth of the limnetic zone) can be measured using a secchi disc.

The lowest zone is home to the profundal zone, where light does not penetrate and the water is colder and heavier. This area is dominated by bacteria and fungi that consume oxygen, rather than produce it.  These organisms break down or consume (decompose) dead plants and animals that settle out of the waters above.

The bottom, where water meets the sediment, is called the “benthic zone.”


Sunlight Drives Most Lake Processes.  Sunlight determines the width and maximum depth of the littoral zone, the home of aquatic life crucial to a lake's health.  It also determines the depth of the thermocline, the transition between the warm and cold layers of the lake in summer months. Water clarity, or light penetration, is influenced by amount of phytoplankton (microscopic organisms) that inhabit the upper sunlit layer of a lake.  Excessive phosphorous levels lead to excessive phytoplankton, reduced clarity, and a reduction in water quality.  We measure water clarity using a device called a Secchi disc, and these measurements help us monitor water quality over the summer months.

Lake Ecosystems Need Nutrients and Oxygen: All plants need an appropriate balance of the essential nutrients phosphorous, nitrogen, and carbon.  The nutrient that is in shortest supply relative to the plant’s need will limit the growth of the plants. This is called the limited nutrient concept.  In the case of Lake Harwinton, phosphorous is the limiting nutrient, and so it is the most important nutrient to control.  An increase of phosphorous in the water increases algae, which in turn decreases water clarity and quality.  We monitor both P and N levels over the course of the summer.

Dissolved oxygen (DO) is oxygen that floats freely in the water in the form of gas.  It can be blown into the water by wind, gradually enter the water at the surface, or be created by organisms performing photosynthesis.  Oxygen is essential to support fish and other animals in our lake.  Lake Harwinton has sufficient oxygen levels to support aquatic life above the thermocline, or about 10 feet.

Lakes Get Old:  The aging process of a lake is called eutrophication.  Natural eutrophication occurs over hundreds of years, as a lake fills with sediments, plants and debris.  Nutrients flowing into the lake from the watershed increase growth of plants, which die and sink to the bottom. Then "decomposers" (bacteria and fungi) use the oxygen in the process of breaking down the algae. This creates very low oxygen levels ("hypoxia") or even a nearly complete lack of oxygen ("anoxia") in the bottom layer of the lake. These conditions are dangerous for lake organisms like fish, which need oxygen to live.  We monitor DO and the depth of the anoxic layer to assess water quality trends.

Lakes age more quickly when humans get involved by overfeeding the environment with nutrients.  These extra nutrients speed up the aging process by promoting algae and excessive weed growth.  As the algae die, the decomposition process depletes the oxygen in the lake, and the phosphorous can become available for new growth, and the cycle continues.  The best way to slow down this aging process is to limit nutrients coming into the lake.


A lake’s "trophic state" defines where it falls on the age spectrum.  Lakes categorized as oligotrophic have low concentrations of nutrients, do not support much biological activity such as fish or plant growth, have high amounts of dissolved oxygen, and have relatively clear water. They are often deep and have rocky or sandy shorelines. Lakes with high concentrations of nutrients are called eutrophic. These lakes often have a mucky bottom, support large amounts of plant and fish growth, have low amounts of dissolved oxygen in bottom waters, and often look murky. Lakes in between oligotrophic and eutrophic are known as mesotrophic, and they have a range of intermediate conditions.

Based on the baseline monitoring we have been doing, Lake Harwinton is classified as mesotrophic, or "middle aged".


Cultural eutrophication: The rate at which a lake receives nutrients and sediments from its watershed determines the rate of eutrophication, or aging. Under natural conditions eutrophication occurs over a long period, often centuries.  The aging process speeds up considerably, however, when the amount of plant nutrients and sediments that drain into a lake increases due to human activities. The term commonly used when eutrophication is accelerated by these man-made conditions is cultural eutrophication.

Effects of cultural eutrophication can occur in a short period of time, a few decades or less. Dissolved nutrients, including phosphorus and nitrogen, fertilize the water environment and stimulate algae and weed growth.  Sediment particles also carry nutrients that eventually become available to aquatic plants in the lake. In addition, sediments settling on the bottom make the lake shallower.

Phosphorous is the biggest factor: The nutrient in the shortest supply relative to the needs of an organism is called the limiting nutrient. When the limiting nutrient is depleted, growth stops, even though other nutrients remain available. Any increase in the supply of the limiting nutrient results in a corresponding increase in growth, as any decrease in the supply results in a decrease in growth. The supply of the limiting nutrient controls the growth of algae and aquatic weeds in a lake.  Phosphorus is the limiting nutrient for the growth of algae in Lake Harwinton

Problems resulting from eutrophication:  Typical problems associated with accelerated eutrophication include algae blooms, excessive weeds, and sedimentation.  In addition to eutrophication, non-native aquatic plants are a serious threat to our lake's health.  Each of these problems are discussed below

1. Algae Blooms

Algae are microscopic plants that are vital components of the lake ecosystem. Algae serve as sources of food and energy for fish and other lake organisms. Excessive algae growths, however, occur as “blooms” that have a pea soup appearance and can form scums and mats on a lake’s surface.  When blooms die, the plant matter decomposes, depleting oxygen in lake waters, which can cause a fish kill. The presence of frequent algae blooms usually indicates that phosphorus levels in the water are high.  The best way to eliminate algae blooms is to reduce phosphorous.


The types of algae that we have encountered problems with include:


Filamentous algae: (the pillows of green cotton candy)  More information:  PSU_Filamentous


Chara and Nitella: Plant-like Algae (these look almost identical to a weed, but they are algae!)   More information:  PSU_Chara and Nitella


"Blue-Green" algae (cyanobacteria) Some blue-green algae produce toxins that could pose a health risk to people and animals when they are exposed to them in large enough quantities. For more information, go to Blue-Green Algae Information.


Planktonic algae (microscopic plants that make the water green)  More information: PSU_Planktonic


2. Excessive Weeds, or Macrophytes

Macrophytes are large aquatic plants that, like algae, are vital components of a lake ecosystem.  They provide cover for fish and food for wildlife.  However, too many nutrients cause large, dense weed beds to grow and become a nuisance. The key to preventing excessive weed growth is a watershed management program to reduce nutrients flowing into the lake. We have encountered excessive amounts of Elodea and Narrow Leaf Pondweed in the past at Lake Harwinton.  The pictures below can help you to identify them.

Elodea.  A rooted dark green native plant with three whorls of three leaves.  Looks similar to the invasive hydrilla.  More information:  ME_Elodea


Slender Pondweed - Native ( aka Berchtold's Pondweed, narrow leaf pondweed)   More information: ME_SlenderPondweeds-Bercholds





3.  Sedimentation:  Storm water move soils, road sand, and other contaminants from the watershed directly into the lake.  A watershed survey has been conducted to identify sites where runoff water is being compromised by erosion.  Locations around the lake where remediation is needed have been identified.  Remediation is expensive, however, which is why we have started a watershed improvement fund to cover capital projects.  The scope and planned timing of these projects is outlined in the Lake Management Plan.

In addition to capital projects involving inlets and roadways, a significant impact can be made by property owners in the watershed to prevent erosion.  Silt fences should be used when undertaking any landscaping project that exposes soil to erosion.  Lakefront owners should create a vegetated buffer zone, for keeping both sediment and nutrients out of the lake.  See the "what you can do" section.

4. Non-native aquatic plants:  Non-native plants have the potential to become invasive and dominate the shoreline, seriously hampering recreational activities. Once introduced, 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.  The key to prevention is to follow boat cleaning practices when moving boats of any kind from one lake to another.  Some of the worst that other lakes are battling are milfoil, fanwort, and hydrilla.  Lake Harwinton is fortunate in that so far, we have not been invaded by these species.  Here is one invasive we encountered late last year:

Spiny Naiad (najas minor):  Also known as European Naiad, they are easily confused with native naids and some narrow leaf pondweeds.  More information:  ME_Naiads-Spiny  (link)


Identifying weeds is challenging; this source is very good:   CT_Invasive-Plants-Field-Guide (CAES-2010). 

5. Other Threats:  Humans contribute a great deal of salts, detergents, caffeine, fire retardants, manufacturing chemicals, and heavy metals to water bodies around the world, including ours. These dissolved substances can negatively affect aquatic ecosystems. It is important for you to be conscious of the waste that you produce and where it is going to most effectively protect the environment from exposure to toxic pollution. Use our town hazardous waste collection days to keep toxic chemicals out of our lake!



Set a goal and objective:  Our overall goal is to increase water quality, and the key objective that supports this is to reduce the phosphorous load in our lake.  Phosphorous is the main driver of algae blooms and eutrophication; just tiny amounts have a huge impact on algae growth, so this is the focus.  If we want to eliminate algae blooms, we must reduce phosphorous in our lake, and the focus should be narrowed to what we CAN manage:  the locally controlled phosphorous. This illustration makes it very clear:



Get started:  First we must recognize that lakes are vulnerable-that in order to make them thrive, we, both individually and collectively, must assume responsibility for their care.  Next we need to implement the process of lake water quality management.  This involves taking an active role in altering certain ecological relationships within the lake and its watershed to make a lake healthy and keep it healthy.

Get some help and guidance:  Lake Management is a complex process, so we contracted with a limnologist to assist us. A limnologist, sometimes called a lake manager, is trained to look at our lake as a whole, and assess its overall health, help resolve current problems, and guide us in developing a long term solutions to our lake's health problems.

Get the components of Lake Water Quality Management in place:  Connecticut DEEP specifies these components of Lake Water Quality Management:

  • Baseline Monitoring - Water quality monitoring is conducted to assess the extent of eutrophication. Over time, baseline monitoring is repeated to evaluate trends in water quality conditions, identify changing conditions, identify problems, and to measure progress of short term management actions.  We started to monitor water quality data in 2012, and we will continue to do so.  The 2017 Water Quality Report can be found in the Reference Materials page.
  • 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.  Refer to 2012 Water Quality Survey, performed by our limnologist. 
  • 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. An assessment was performed in 2013/14 which concluded our watershed is generally in good condition, with healthy stream systems and wetlands.  Recommendations were made and specific sites were identified that need remediation to reduce the flow of nutrients into our lake
  • Management Plan - The results of the diagnostic study and watershed assessment are used to formulate a plan that implements best management practices ("BMP's") control sources of pollution in our watershed and prevent further deterioration. The Lake Management plan includes both watershed and in-lake BMP's.  Some of these practices are easy and relatively inexpensive, but some are longer term expensive projects identified in the watershed assessment.  A Watershed Capital Improvement fund was created to fund these projects.

This plan sounds good, but what about NOW?  "Quick Fixes" are not solutions to the root cause of our water quality problems, but they can become necessary in the short run to preserve recreational value.  In addition to watershed projects, the Water Committee has reviewed many in-lake options for management of algae and rooted plants, but not all are applicable to Lake Harwinton, and others are infeasible, unproven, or not financially justified.  Historically we have used herbicides and algaecides when absolutely necessary, and we are exploring the use of harvesting in some sections of the lake.  The "in-lake" methods we are using to manage our most common problems are:

  • Filamentous algae:  A copper based algaecide that is reasonably effective applied at the right time.  It is better to harvest the stuff and dispose of it outside of the watershed.  If we kill it, it sinks, decomposes, depletes oxygen, and frees up more nutrients for more undesirable growth.
  • Blue-green algae:  This is very difficult to control.  Also known as cyanobacteria, this form of algae can be (but is not always) toxic.  A copper based algaecide is somewhat effective, but caution must be used in using algaecide on toxic blue greens, because the algae release the toxins when they die.  We do not consider treatment unless water clarity goes below 4 or 5 feet.
  •  Elodea, narrow leaf pondweed:  Spot treatment with the herbicide Diquat.  It usually dies after a week or so, but can rise in the decomposition and create floating biomasses.  These are best harvested and removed form the watershed.
  • Spiny naiads, native naiads:  Spot treat with the herbicide Diquat, as above.

We use these methods with caution due to the high risk of unintended consequences.  For example, harvesting can encourage more robust plant growth and spread fragments that will grow new plants.  Using a herbicide or algaecide to kill one species may open the door for an even more obnoxious species to replace it.   The algae Chara is a good example of this.  It is a mild nuisance (tickles the ankles), but it acts as a "nutrient sink" by tying up phosphorous that could otherwise trigger the growth of blue green algae or an aggressive weed.

Each year seems to be different in terms of the species and nuisance level of algae and weed problems Lake Harwinton experiences.  The list of variables includes not only average temperature and average rainfall, but also the impact of extreme rainfall flushing the watershed.   Dealing with a lake's problems can be discouraging, since it seems like we are fighting a losing battle with mother nature.  We CAN manage the locally controlled sources and make a difference in our lake water quality.  We'll cover what can be done in the next section.

WHAT CAN YOU DO?             

Do not use fertilizers and pesticides on your lawn. This applies to ALL properties in the watershed, not just lake front owners.  Even organic material such as grass clippings and fallen leaves contribute extra nutrients to the ecosystem when they breakdown. Bag and dispose of them properly or add them to a compost bin away from the water to prevent concentrated nutrients from decomposing material from entering the lake.

Maintain Your Septic System. Pump the septic tank and inspect the system at least every 3 years.  A septic system is a multi-step process to treat human wastes. Wastes flow into a tank where the solids settle out. The liquids then flow into a drain field where they are decomposed by soil microbes. These wastes are very high in nutrients. When properly maintained, septic systems can effectively reduce the amount of nutrients entering our lake.

Prevent the Spread of Invasive Species. An invasive species of plant or animal is often called an aquatic hitchhiker, because they spread by catching rides on boats and equipment moved from one lake to another.  Anglers, kayakers, canoeists, boaters and even swimmers with water toys can all unknowingly spread unwanted organisms.  Microscopic cells can cling to fishing gear, waders, boots and boats, and remain viable for months under even slightly moist conditions.  To prevent the spread of invasives, boaters and anglers must practice CHECK, CLEAN, DRY procedures on their boats and equipment. CT DEEP has a good brochure on this topic: 

Managing Your Shoreline. A properly managed shoreline filters out harmful pollutants in runoff, provides habitat for all sorts of creatures, and stabilizes the soil around the lake to reduce erosion.  We encourage lakefront property owners leave an unmanaged area of land, called a buffer zone, between their house and the water where appropriate grasses, plants, and shrubs can mature to promote a healthy shoreline.  Check out our references page, contact the Water Committee via our website to borrow a book that will assist you.   

Conserve Your Water. When you conserve water in your home and yard, you also reduce the amount of harmful substances that can find their way into your lake.  Make minor changes in your everyday routine: take shorter showers, install low-flow shower heads, repair leaky faucets, avoid washing your car or boat in areas that drain directly into your lake, and only run your washing machine and dishwasher when they are full.

Collect rainwater in a rain barrel to give your usual water supply a break.  This will, reduce water pollution by trapping water before it accumulates contaminants that can be transported to your lake. Consider creating a rain garden! These are gardens designed to have storm water drain into them. They act as a natural filter so harmful pollutants in runoff water are trapped

Discourage Canada Geese. Studies have shown that one average goose can generate three pounds of nutrient-rich waste every day.   It is important that we discourage these unwanted visitors from overstaying their welcome.  Easy steps include:

  • DO NOT feed the geese
  • Keeping a natural zone of vegetation between your grassy lawn and the lake shore
  • Creating a simple rope or wire barrier along your shoreline

Properly Dispose of Pet Waste.  Waste stations are provided around the lake to provide disposal bags for pet waste, which should then be placed in the trash.  Use them please!

Volunteer.  Our lake association organizes work parties to clean up beaches, drain basins, and other sources of sediment and nutrients.  These activities not only make our lake look better, but they alss reduce the amount of nutrients in the lake.  

Stay Informed.  Knowledgeable members make better custodians of our lake.  If you see an article in the paper, read it! Keep an eye on our website for any new information.
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