What is a Secchi Disk?

A Secchi disk is an 8-inch Diameter disk with alternating black and white quadrants. It is lowered into the water of a lake until it can be no longer seen by the observer. This depth of disappearance, called the Secchi depth, is a measure of the transparency of the water.

Transparency can be affected by the color of the water, algae, and suspended sediments. Transparency decreases as color, suspended sediments, or algal abundance increases.

Water is often stained yellow or brown by decaying plant matter. In bogs and some lakes the brown stain can make the water the color of strong tea. Algae are small, green aquatic plants whose abundance is related to the amount of plant nutrients, especially phosphorus and nitrogen.

Transparency can therefore be affected by the amount of plant nutrients coming into the lake from sources such as rain runoff, septic tanks, and lawn and agricultural fertilizer. Suspended sediments often come from sources such as resuspension from the lake bottom, construction sites, agricultural fields, and urban storm runoff.

Transparency is an indicator of the impact of human activity on the land surrounding the lake. If transparency is measured through the season and from year to year, trends in transparency may be observed. Transparency can serve as an early-warning that activities on the land are having an effect on its quality.

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TMDL Definition

What is a total maximum daily load (TMDL)?

A TMDL or Total Maximum Daily Load is a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards, and an allocation of that amount to the pollutant’s sources.

Water quality standards are set by States, Territories, and Tribes. They identify the uses for each waterbody, for example, drinking water supply, contact recreation (swimming), and aquatic life support (fishing), and the scientific criteria to support that use.

A TMDL is the sum of the allowable loads of a single pollutant from all contributing point and nonpoint sources. The calculation must include a margin of safety to ensure that the waterbody can be used for the purposes the State has designated. The calculation must also account for seasonable variation in water quality.

The Clean Water Act, section 303, establishes the water quality standards and TMDL programs

Reflecting on Lakes

How protecting your watershed can improve your lake

A high quality lake, valued for recreation and aesthetic appeal, can benefit all watershed residents (and nonresidents alike) by providing a healthy place to play and/or enjoy a quiet sunset. In other words, a high quality lake improves the quality of the community’s life. Property values, not only on the lakeshore, but throughout the watershed community, can benefit from a desirable lake.

Six keys to protecting lakes

  1. Valuing high quality lakes
  2. Understanding the link between the lake and its watershed
  3. Understanding in-lake processes
  4. Recognizing and preventing threats to lake quality
  5. Forming partnerships with lake-watershed members
  6. Knowing where to go for help

A lake is the reflection of its watershed (the land that drains — eventually — into it) and the everyday actions that take place on the watershed. The importance of the relationship between a lake and its watershed cannot be over emphasized when protecting, managing or restoring a lake. The lake-watershed “system” is a functioning unit with interacting biological, physical, chemical and human components.

If a lake suffers from problems such as extensive weed growth or algal scum, fish kills, or filling in with sediments, often the cause of the problem can be linked to a source or sources within the watershed.

The characteristics of lake-watershed interaction depend on a number of variables. Some variables include the ratio of drainage area to lake area, how the land is used, the climate, soils and geography, as well as existing conservation measures.

Sizes and shapes

The origin of a lake often determines the size and other characteristics of the lake. “Man-made” lakes, often referred to as impoundments or reservoirs, are those that were formed by damming a drainageway, stream or river. Man-made lakes can range in size and shape from the smallest farm pond to huge “run-of the-river” reservoirs such as Lake Mead formed by the Hoover Dam.

Lake-watershed size relationship

If a lake is small relative to its watershed, the potential is greater for the lake to fill in with sediment or be affected by nutrients tied to the soil particles, than a large lake with a relatively small watershed.

Climate and soils

Lakes in areas with more rainfall and steep, erosive, nutrient-rich soils will have greater potential for algae blooms and plant growth than those in dry climates with infertile soils.

Topographic

In general, the greater the slope of the land in the lake’s watershed, the greater the potential of pollutants reaching the lake.

Lake productivity stages

In-lake factors combined with the lake-watershed relationship, determine how “productive” a lake will be. The biological productivity of a lake is based on the availability of plant nutrients and is referred to as the lakes “trophic” condition. Extremely high or low productivity usually limits aquatic life. High productivity leads to lots of algae and other aquatic plants. Low productivity leads to very little aquatic life.

The trophic condition of lakes ranges from the least productive (oligotrophic) to moderately productive (mesotrophic) to highly productive (eutrophic). Hypereutrophic lakes are the most productive of all. The process of moving from an oligotrophic state to a eutrophic state, is a natural process that can take thousands of years, as sediment from the watershed carries nutrients slowly into the lake.

However, where human activity has affected a watershed, lake productivity can dramatically increase over a relatively shorter period of time. This type of eutrophication–as a result of watershed disturbance by humans — is known as “cultural” eutrophication.

People, Lakes and Land

People, Lakes, and Land: Puzzling Relationships

In the early years of what is now called “lake management”, scientists and citizens alike focused on restoring the quality of degraded lakes through a myriad of in-lake techniques and activities in the near-shore area. Simple predictive models were used and goal-setting tended to be neglected. If goals were mentioned, they often were wishful comparisons with pristine environments elsewhere. Often, similar management techniques were used from lake to lake forgetting that “lake management is lake specific”.

As the science of lake management evolved it became obvious that focusing exclusively on a lake was not enough — we had to consider the watershed as well. This expansion of focus created not only new partners in lake management but new challenges as well. It improved our predictive tools, enhanced our understanding of the relationships between lakes and watersheds, and created opportunities to involve more people in lake management.

The evolution of lake management continues. Today, we are building broader relationships that look at regional and national lake and landscape patterns. This has improved our understanding of the potential relationships between lakes and the broader patterns of our landscape. This new vision has improved our ability to set resource goals and increase the emphasis on protecting lakes rather than expensive restoration efforts.

However, at each step in the evolution of lake management, it has become increasingly important to take into account the people who are involved, be they lakeshore residents, local planning and zoning authorities, university staff, consultants, or government resource managers. Developing good working relationships between these and all other groups involved ultimately will do the most to protect our lake resources.

Thus, the people side of lake management has become increasingly important. It means we have had to improve our skills for dealing with each other as individuals or organizations, and for managing and nurturing volunteers, educating people on lake and land stewardship, and working to change attitudes on how lakes should be used or shoreline areas managed.

It seems safe to say the continuing development of relationships between people, lakes, and land will create new and challenging problems for lake management. But, by building partnerships, and remembering that “lake management is lake specific”, these challenges will be puzzling but not impossible.

Lake Restoration

Lake Restoration Versus Lake Management?

A complex and potentially controversial topic that can mean various things to different lake user groups. Lake restoration often connotates attempting to return a lake to an original or previous condition – usually with a desire for clearer water (less algae) and fewer vascular plants, by the recreational user.

Management, on the other hand, typically refers to action(s) taken to produce a desired condition. Once the ecological balance has been altered, either through human intervention or acts of nature, the lake system can never truly be “restored” but only “managed.” Prudent “management” of our valuable pond/lake resources is a shared responsibility between the lake user/owner, professional lake managers and the regulatory community.

Dredging Not Always a Solution to Lake Problems

Dredging is often an appropriate lake management technique to provide added water depth and volume and potentially remove nutrient reserves that continue to support nuisance vascular plants and algae. In some situations, dredging will also reduce the abundance of rooted aquatic plants, primarily through limitation of light penetration and to a lesser extent by changes in bottom substrate.

During the 1970’s and 80’s USEPA and state agencies funded a number of New England dredging projects, each to the tune of several hundred thousand dollars or more. Specific dredging projects that come to mind include: Nuttings Lake (Billerica, MA), Morses Pond (Wellesley, MA) and 1860 Reservoir (Wethersfield, CT). A primary goal in dredging all of these waterbodies was to provide long-term control of nuisance rooted vegetation and/or algae. Within roughly 1-2 years from completion of dredging, however, these same lake communities experienced severe nuisance weed/algae conditions.

At Morses Pond, there is a reason to believe the pond dredging actually spread the plant (milfoil) infestation. What went wrong with these projects? To some extent, the potential benefits of dredging were “oversold” by the project proponents particularly in light of the limits imposed by funding and disposal options. Seldom will dredging alone, control invasive plants like milfoil through changes in bottom substrate.

Groundwater & Surface Water

Understanding the Interaction

Test your groundwater IQ.

1. Which ways can groundwater move?

a. Up / b. Down / c. Sideways / d. All of the above

2. How is the speed of groundwater movement measured?

a. Feet per day / b. Feet per week / c. Feet per month / d. Feet per year

3. How is stream flow usually measured?

a. Feet per second / b. Feet per minute / c. Feet per hour / d. Yards per hour

4. What determines how fast groundwater moves?

a. Temperature / b. Air pressure / c. Depth of water table / d. Size of materials

5. Can the water table elevation change often?

a. Yes / b. No

Does aquifer storage capacity vary?

a. Yes / b. No

Answers:

1. d. All of the above Although most movement is lateral (sideways), it can move straight up or down. Groundwater simply follows the path of least resistance by moving from higher pressure zones to lower pressure zones.

2. d. Feet per year Groundwater movement is usually measured in feet per year. This is why a pollutant that enters groundwater requires many years before it purifies itself or is carried to a monitored well.

3. a. Feet per second Water flow in streams/rivers is measured in feet per second.

4. d. Size of materials Coarse materials like sand and gravel allow water to move rapidly. (They also form excellent aquifers because of their holding capacity.) In contrast, fine-grained materials, like clay or shale, are very difficult for water to move through. Thus, water moves very, very slowly in these materials.

5. a. Yes Water table elevations often fluctuate because of recharge and discharge variations. They generally peak in the winter and spring due to recharge from rains and snow melt. Throughout the summer the water table commonly declines due to evaporation, uptake by plants (transpiration), increased public use, industrial use, and crop, golf course and lawn irrigation. Elevations commonly reach their lowest point in early fall.

6. a. Yes Just like the water level in rivers and streams, the amount of water in the groundwater supply can vary due to seasonal, weather, use and other factors.

Groundwater: A Hidden Resource

Groundwater is a hidden resource. At one time, its purity and availability were taken for granted. Now contamination and availability are serious issues. Some interesting facts to consider… Scientists estimate groundwater accounts for more than 95% of all fresh water availablefor use.Approximately 50% of Americans obtain all or part of their drinking water fromgroundwater.

Nearly 95% of rural residents rely on groundwater for their drinking supply. About half of irrigated cropland uses groundwater. Approximately one third of industrial water needs are fulfilled by using groundwater. About 40% of river flow nationwide (on average) depends on groundwater. Thus, groundwater is a critical component of management plans developed by an increasing number of watershed partnerships.

Groundwater ABCs

Groundwater is the water that saturates the tiny spaces between alluvial material (sand, gravel, silt, clay) or the crevices or fractures in rocks.

Aeration zone: The zone above the water table is known as the zone of aeration (unsaturated or vadose zone). Water in the soil (in the ground but above the water table) is referred to as soil moisture. Spaces between soil, gravel and rock are filled with water (suspended) and air.

Capillary water: Just above the water table, in the aeration zone, is capillary water that moves upward from the water table by capillary action. This water can move slowly in any direction, from a wet particle to a dry one. While most plants rely on moisture from precipitation that is present in the unsaturated zone, their roots may also tap into capillary water or into the underlying saturated zone. Aquifer: Most groundwater is found in aquifers-underground layers of porous rock that are saturated from above or from structures sloping toward it.

Aquifer capacity is determined by the porosity of the subsurface material and its area. Under most of the United States, there are two major types of aquifers: confined and unconfined. Confined aquifers (also known as artesian or pressure aquifers) exist where the groundwater system is between layers of clay, dense rock or other materials with very low permeability.

Water in confined aquifers may be very old, arriving millions of years ago. It’s also under more pressure than unconfined aquifers. Thus, when tapped by a well, water is forced up, sometimes above the soil surface. This is how a flowing artesian well is formed. Unconfined aquifers are more common and do not have a low-permeability deposit above it. Water in unconfined aquifers may have arrived recently by percolating through the land surface. This is why water in unconfined aquifers is often considered very young, in geologic time. In fact, the top layer of an unconfined aquifer is the water table. It’s affected by atmospheric pressure and changing hydrologic conditions. Discharge and recharge rates depend on the hydrologic conditions above them.

Saturation zone: The portion that’s saturated with water is called the zone of saturation. The upper surface of this zone, open to atmospheric pressure, is known as the water table (phreatic surface). How Groundwater and Surface Water connect. It’s crystal clear. Groundwater and surface water are fundamentally interconnected. In fact, it is often difficult to separate the two because they “feed” each other. This is why one can contaminate the other.

A closer look.

To better understand the connection, take a closer look at the various zones and actions. A way to study this is by understanding how water recycles … the hydrologic (water) cycle. As rain or snow falls to the earth’s surface: Some water runs off the land to rivers, lakes, streams and oceans (surface water). Water also can move into those bodies by percolation below ground.

Water entering the soil can infiltrate deeper to reach groundwater which can discharge to surface water or return to the surface through wells, springs and marshes. Here it becomes surface water again. And, upon evaporation, it completes the cycle. This movement of water between the earth and the atmosphere through evaporation, precipitation, infiltration and runoff is continuous.

How groundwater “feeds” surface water.

One of the most commonly used forms of groundwater comes from unconfined shallow water table aquifers. These aquifers are major sources of drinking and irrigation water. They also interact closely with streams, sometimes flowing (discharging) water into a stream or lake and sometimes receiving water from the stream or lake. An unconfined aquifer that feeds streams is said to provide the stream’s baseflow. (This is called a gaining stream.) In fact, groundwater can be responsible for maintaining the hydrologic balance of surface streams, springs, lakes, wetlands and marshes.

This is why successful watershed partnerships with a special interest in a particular stream, lake or other surface waterbody always have a special interest in the unconfined aquifer, adjacent to the water body.

How surface water “feeds” groundwater.

The source of groundwater (recharge) is through precipitation or surface water that percolates downward. Approximately 5-50% (depending on climate, land use, soil type, geology and many other factors) of annual precipitation results in groundwater recharge. In some areas, streams literally recharge the aquifer through stream bed infiltration, called losing streams.

Left untouched, groundwater naturally arrives at a balance, discharging and recharging depending on hydrologic conditions. Common boundaries.

Aquifers are often difficult to delineate. It requires someone with an understanding of the aquifer, the geology, the surface above it, and the land that drains toward the surface. An unconfined aquifer area often extends to the surface waterbody’s (i.e. lake, river, estuary) watershed. When determining an aquifer protection area, pumping (working) wells are not considered. The biggest risk to an unconfined aquifer is contaminated water moving through the permeable materials directly above it. This area is known as the primary recharge area. Depending on the depth and overlying geologic characteristics, travel time from the surface to the aquifer can be relatively short.

When pumping wells are located near a stream or lake, infiltration can be increased. Infiltrating streams typically provide an aquifer with large quantities of water and a pathway for bacteria, viruses and other contaminants.

A confined aquifer area may be limited to the outcrop of the aquifer unit and its immediate contributing area. This area may actually be isolated from the location of water supply wells within the aquifer. Semi-confined aquifers may receive water from both outcrop areas and overlying aquifers. Delineating the aquifer protection area can be extensive and complex. Sole-source aquifers are delineated based on aquifer type – confined, semi – confined or unconfined – and local geologic and hydrologic conditions. Defined as providing a minimum of 50% of the water for its users, sole-source aquifers usually exist only where there simply are no viable alternative water sources.

Wellhead protection areas (also known as zone of contribution and contributing areas) are the surface and subsurface areas surrounding a well or field of wells (wellfield) supplying a public water system.

Threats to quantity.

When an increased quantity of groundwater is being withdrawn to meet the demands of a growing population, typical threats such as overdraft, drawdown and subsidence can occur. Overdraft occurs when groundwater is removed faster than recharge can replace it. This can result in a permanent loss of a portion of its storage capacity. A change that can cause water of unusable quality to contaminate good water. Generally, any withdrawal in excess of safe yield (the amount that can be withdrawn without producing an undesirable result) is an overdraft.

Drawdown differs significantly from overdraft. It results in a temporarily lowered water table generally caused by pumping. In this situation, the water table recovers when the supply is replenished. Subsidence is one of the dramatic results from overpumping. As the water table declines, water pressure is reduced. This causes the fine particles that held water to become compacted. In addition to permanently reducing storage capacity, the land above the aquifer can sink … from a few inches to several feet … causing a sinkhole. This can damage property and fields.

Eutrophication

What is Eutrophication?

The term eutrophication is now generally used, even by most scientists, to describe both nutrient levels (the amount of foodstuff available for plant growth) and the natural “aging” of a lake. Eutrophication is the process of increased nutrient input to a lake over the natural supply. From the instant that a lake is created, the aging process, or filling-in, begins. Material is carried from the watershed by streams, wind and direct runoff to become deposited in the lake. They also age at different rates because of differences in geology, runoff and watershed characteristics.

Bungay is considered a eutrophic lake, one which is shallow with a soft mucky bottom. Rooted plant growth is abundant along the shores and out into the lake, while algae blooms are not unusual. The water is often colored, with suspended and organic matter reducing its clarity. Eutrophic lakes support only warm water fisheries such as perch, horned pout and bass.

Any activity in which man increases the rate of incoming materials (such as land clearing, and watershed development) or increases the nutrient loading (septic leaching, fertilizers, etc.) will hasten this aging process. This is often called cultural eutrophication.

Why has Bungay filled in or “aged” so much over the past 40 years?

As we learned above, all lakes gradually fill in over time. If a lake is experiencing a nutrient overload, it will fill in much faster that one that isn’t. At one time, Bungay Lake used to be 90% summer cottages. Over the past 30/40 years, we’ve reversed that to 90% full time residences. This results in nutrient overload that is nearly 6 to 10 times the previous amount. The chart below shows typical phosphorus levels for cottage living compared to year round living.

Cottage Living

-Human Waste = 534 grams, -No Dishwasher = 0 grams, -Doesn’t Fertilize = 0 grams, -Wooded Lot = 17 grams, -Phosphate Free Household Products = 0 grams, -Total = 551 grams

Year Round Residence

Human Waste = 1534 grams, -Dishwasher, Powdered Detergent = 651 grams, -Fertilizes Lawn Twice per Year = 1962 grams, -Clears Lot = 29 grams, -Household Products Containing Phosphates = 180 grams, -Total = 4356 grams

Bungay Lake is the way it is today mostly because of the way we have been treating it over the past several years. See articles on nutrient reduction in this archive to discover what YOU can do to help prevent nutrient overloading.

Dredging Defined

What Is Meant By Dredging?

Dredging is basically the removal of sediment and other material from a lake or pond and there are two basic types. “Dry dredging” is a process of draining the lake completely and using heavy machinery to remove the sediment and gravel. “Wet dredging” removes the material while it’s still under water, using a barge and vacuum pumping system, allowing the lake to still be partially used. Either way you get there, dredging has its benefits and detriments.

Benefits:

  • Increasing the depth of shallow lakes has long-term advantages. Adequate depth promotes fish growth, discourages weed growth, lowers water temperatures, increased oxygen levels, and recreational boating opportunities.
  • Dredging can effectively remove plants, organic matter and nutrients. The removal of nutrients and sediment will reduce the internal nutrient loading, and help to discourage further growth of some types of algae and weeds.
  • dredging can be site specific and directed at target areas.

Detriments:

  • cost
  • depending on the method used, you may temporarily displace or kill some of the living organisms including fish and bethnics.
  • portions of the use of the lake for human activities are precluded during dredging.
  • disposal of the dredged spoils is costly and may pose environmental impacts.
  • dredging should not be viewed as a viable method for managing aquatic weed and algae growth. Only about 10% of the ponds that have been dredged in New England for the purpose of managing plant growth have effective management for more than two years. Most lakes experience a regrowth of aquatic vegetation quite readily after dredging.
  • because dredging does nothing for the nutrient overload being imposed on the lake by its residents, high concentrations of algae is a post-dredging problem.

As with any lake management technique or project, there are advantages and disadvantages to consider.

Effective lake managers must focus on the results and not the activities.

Chapter 91

On May 2nd, 1996, a letter was received from The Commonwealth of Massachusetts Executive Office of Environmental Affairs (Department of Environmental Protection, One Winter Street, Boston, Ma 02108, 617- 292-5500) addressed to the North Attleboro Board of Selectmen. They were asked whether or not Bungay Lake was considered a “great pond” and therefore had to comply to Chapter 91 Regulations (the registering of all docks, retaining walls, etc.)

The following was their response:

“Dear Sir/Madame:

The Department of Environmental Protection, Waterways Regulation Program is responsible for administering and enforcing M.G.L. Chapter 91. Recently, the Program completed an initial review of maps and documents relating to Great Ponds of the Commonwealth. A Great Pond is a lake or pond which was ten acres or more in it’s natural state.

As a result of our preliminary findings, we have determined that there are no Great Ponds within your municipality. However, should anyone have evidence that a Great Pond does lie within the boundaries of your municipality, we will revise the draft list to include that pond.

Sincerely,

Jill E. Provencal, Cartographer, Waterways Regulation Program”
Thanks to all who got involved!

P.S. These findings have nothing to do with Boat Registration! Regulations by the Commonwealth of Massachusetts require registration for all vessels equipped with propulsion. This is enforced by the Massachusetts Environmental Police (as you may have seen!). The Board strongly recommends complying to these regulations. Please call us with any questions.

Bungay Drawdown Comments

During our lake level discussion at the 1998 annual meeting, we had a questions come up about lake drawdown. What effect would lake drawdown have on the non-native species, the desirable native plants, fish and wildlife, etc.?

I posted this questions and our situation up on the internet into some lake and pond management discussion groups. I received some excellent feedback from many professionals in the field including:

  • Scott Seymour, Aquatic Systems Inc., Butler WI, (30 years of Environmental pond and lake management).
  • Dr. Mark D. Mattson, Water resources Research Center, University of Massachusetts.
  • Steve DeKozlowski, South Carolina Department of Natural Resources.
  • Richard S. McVoy, Ph. D., DEP, Office of Watershed Management, Worcester, MA
  • Robert Hartzel, Mass DEM, Office of Water Resources, Boston, Ma, Lakes and Ponds Program.

Below is a summary of all their comments:

To have any effect on the nuisance non-native species (Cobomba and WaterMilfoil), you would have to drawdown the lake low enough for the roots to freeze. Because these roots reside in the sediment or “muck”, this would mean a drawdown of 6 to 8 feet. In a lake that’s only 12 to 15 feet deep, this would have adverse effects in many other areas.

The native plant Vallisneria (eel grass), which is very desirable, grows in the shallows and could potentially get wiped out in the process. This plant (which is seed germinating) actually acts as a barrier and helps keep out many non-native species (which reproduce by fragmentation). This much drawdown would also deplete the dissolved oxygen supply resulting in a potential winter fish kill. It would not have any impact on the algae condition since this is a nutrient overload issue.

Many studies show that even after such a drawdown, there’s no guarantee that the non-native plants won’t come back the following year. Your best bet is to keep the lake at it highest maintainable level year round and look into other forms of nuisance plant management control.