Click on a topic below for information about Lake Singletary's water quality.
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Mass
Water Watch Partnership - Volunteer Water Quality Monitoring
Mass WWP is a volunteer
water quality-monitoring organization based at U Mass, Amherst. Their mission is
to train and support volunteers to perform water quality sampling and analysis.
Our sampling program
began in 1994 and is still going strong! Our volunteers sample every month
between April and October for clarity, pH, alkalinity, dissolved oxygen,
temperature, phosphorus, and chlorophyll. Although the UMass Water Quality Lab
analyzes samples for phosphorus and chlorophyll, our volunteers perform all
other tests.
The data provides
important information about the condition of our lake. Over time we will be able
to look for trends to determine whether the water quality is changing.
Click on the links below
to see photos of our volunteers.
Interpreting
Water Quality Data
Our data has been used
to help us with our Lake Management Plan. Consultants such as Gerry Smith from
Aquatic Control Technology, Inc., Fugro East, Inc. (now ENSR), and Beta
Engineering, Inc., have used the data, and have provided us with valuable
information and interpretation to help us determine what course of action to
take to protect water quality.
This page was developed
to inform and educate Lake Singletary Watershed Association members about the
health of our lake. References used include "A Primer on Limnology",
by Bruce Monson, "Understanding Lake Data", by Byron Shaw, et al., and
"The Lake Book", by Libby Moore.
Trophic state is a
method to classify lakes and is an indicator of water quality. Common
characteristics used are clarity, chlorophyll (a measure of algae present), and
total phosphorus concentration.
Oligotrophic
lakes have low nutrient content, and thus are very clear, produce few weeds, and
do not support large fish populations. Eutrophic
lakes are rich in nutrients, are subject to frequent algae blooms, and support
large plant and fish populations. Eutrophic lakes, however, may be subject to
oxygen depletion resulting in fish kills. Mesotrophic
lakes lie between these two states. Lake Singletary is classified as
mesotrophic.
The transition from
oligotrophic to eutrophic is part of the natural aging process of a lake, but
human activities accelerate this process. The introduction of nutrients from the
watershed leads to algae blooms, oxygen depletion, and weed growth.
Nutrients are introduced
by non-point source pollution.
Rainfall and subsequent runoff carry nutrients and pollutants from the watershed
into the lake. Effluents from shoreline septic systems are an important
non-point source of nutrients. Soil erosion from construction sites also
introduces nutrients. In addition, erosion contributes to sedimentation and
turbidity, and can be harmful to fish and aquatic organisms.
Non-point source
pollution is difficult to control, because nutrients are introduced at
relatively small concentrations over large areas. Land-use management strategies
in the watershed must be implemented to control this type of pollution.
Clarity
is an important physical characteristic because it gives an indication of the
overall water quality. High levels of nutrients cause dense algae blooms in a
lake. The resulting brown or green color reduces water transparency
significantly. Clarity, however, is not an indicator of pure water. Many toxins
are invisible.
Clarity is measured
using a device called a Secchi disk.
This is a disk-shaped piece of plastic divided into four quarters, painted
alternating black and white. The disk is lowered into the water on the end of a
calibrated line. When the disk disappears from view the depth is measured. As it
is pulled up again, a second measurement is taken when the disk reappears. The
average is recorded as the Secchi depth.
Click
here to see Karen taking a Secchi disk measurement.
A Secchi depth value of
4.5 meters is used to characterize very good water quality. Swimming is not
recommended in water where the Secchi depth is less than 1.3 meters. Lake
Singletary’s Secchi depth is generally between 3 and 4 meters, which is
considered good, although we periodically experience clarity at or below 2
meters.
Subsequent to an algae bloom In September of 2001 the Secchi dropped
to 2.4 meters. In August and September of 1998, during a severe algae bloom, the
Secchi depth dropped to below 2 meters - the worst ever recorded at Lake
Singletary.
Click
here to see a summary of the Secchi disk readings.
The amount of chlorophyll
present is also an indicator of clarity. Chlorophyll is the photosynthetic
pigment in all green plants, and is an inexpensive measure of the amount of
algae present.
In 1999 we added chlorophyll to our monthly sampling program. Lake
water is filtered using special apparatus. The filter is then fan-dried and sent
to the U Mass lab, which performs the analysis.
Click
here to see a summary of chlorophyll results.
The main nutrient that
contributes to excessive weed and algae growth in lakes is phosphorus.
Major sources include human and animal wastes, soil erosion, fertilizer runoff
from farms and lawns, and detergents. Because phosphorus acts as a fertilizer,
it is important to prevent its introduction into the lake. Phosphorus levels
should be maintained below 30 micrograms per liter (m g/L) to prevent algae
blooms.
We currently sample the
lake for phosphorus at the surface and bottom, as well as three inlet streams.
The U Mass lab performs the analysis.
Click
here to see a graph of phosphorus data.
Nitrogen is
second only to phosphorus as a nutrient for weeds and algae. Nitrogen may come
from fertilizer, animal wastes, and septic systems.
The ratio between
nitrogen and phosphorus determines which nutrient is the limiting factor for
weed and algae growth. As with most lakes in this region, phosphorus is the
limiting nutrient in Lake Singletary. This means that we can prevent, to some
degree, excessive weed growth and algae blooms by reducing the flow of
phosphorus into the lake.
Highly acidic water can
be harmful to fish and can leach a variety of metals out of the sediments. pH
and alkalinity
are important because they can determine the effect of acid rain on a lake.
Click
here to see a pH meter in use.
pH
is a measurement of the acidity of water. A pH value of 7 is neutral. Lower pH
values indicate acid conditions, and higher values indicate alkaline conditions.
Every 1 pH unit indicates a 10-fold change in acid concentration; therefore,
water with a pH of 6 contains 10 times more acid than water with a pH of 7. pH
is measured using an electronic device called a pH meter. The recommended
minimum pH for a healthy lake is 6.5. Lake Singletary is slightly acidic.
Click
here to see a graph of pH results.
Alkalinity
is a measurement of the lake’s ability to "buffer" or neutralize
acidity. Minerals in the soil and watershed affect a lake’s alkalinity. Lakes
with alkalinity between 2 and 10 mg/L are considered moderately sensitive to
acid rain. Alkalinity is measured by chemical analysis, which can be performed
by trained volunteers using a test kit. Alkalinity measurements show that Lake
Singletary has some buffering capacity, but is somewhat sensitive to acid rain.
Alkalinity
data shows some buffering capacity, but indicates that Lake Singletary borders
on being sensitive to the effects of acid rain.
Click
here to see alkalinity data.
Temperature
and Dissolved Oxygen Profiles
Temperature and
dissolved oxygen (DO)
profiles give us important information about the lake. After the ice leaves in
the spring the water is fairly uniform in temperature and density, allowing the
lake to mix completely. This spring "turnover" recharges the bottom
water with oxygen and brings nutrients to the surface. As summer approaches and
the water surface warms it becomes less dense and "floats" on the
colder layer underneath. Between the two layers is a region called the thermocline,
where the temperature changes rapidly. This "layering" phenomenon,
known as thermal stratification,
inhibits mixing.
The
steep “slope” represents the thermocline region, where the warm and cold
layers meet. Note that in spring and fall - when the lake is “mixed”- there
is no thermocline.
Click
here to see the thermocline graph for 2003.
During stratification
the oxygen in the bottom layer gets depleted due to decay of material in the
bottom sediments. This decay releases nutrients into the water. Stratification
traps these nutrients and enriches the bottom layer of water. Fish kills may
result if DO levels fall too low.
The following graph represents the dissolved oxygen concentration at the lake
bottom. Fish kills may result if DO levels fall below 5 milligrams per liter.
During the summer months Lake Singletary commonly experiences DO under this
threshold at depths below 5 meters.
Click
here to see graph of dissolved oxygen at the lake bottom.
As the weather cools
again in the fall, the density of the surface layer increases, and it gradually
sinks towards the bottom, allowing mixing. During the fall "turnover",
the nutrient-rich bottom layer mixes with the top layer, often resulting in a
fall algae bloom.
Our lake association
purchased an electronic DO / temperature meter using funds from the 1995 DEM
Grant Program. DO and temperatures are measured using a digital electronic meter
with a probe suspended on a calibrated line. As the probe is lowered the DO and
temperature are measured at various depths from the surface to the bottom. The
resulting DO and temperature profiles provide information about stratification.
On the temperature profile chart below a near-vertical line signifies
uniform temperature. The thermocline is the "plateau" region of the
graph. You can see that as summer progresses the thermocline moves deeper and
gets more pronounced. As fall approaches the water mixes and temperature becomes
more uniform again.
Click
here to see the temperature profile chart.
Click
here to see the DO profile chart.
Actions
You Can Take to Protect Lake Singletary
Keep phosphorus out of the lake:
o
Reduce fertilizer use or use low-phosphorus
"lake-friendly" fertilizer
o
Keep a vegetated "buffer" between the
shore and developed land
o
Build responsibly- obtain necessary permits, use
erosion-control barriers such as hay bales and silt fence, minimize disturbed
areas, and mulch and replant as soon as possible
o
Use phosphate-free detergents
o
Maintain your septic system – pump frequently
and conserve water
Protect the view:
o
Maintain low visibility – leave a natural
"buffer" along the shore to protect water quality and wildlife habitat
o
Limit tree cutting within 100 feet from shore
o
Leave the shoreline in its natural state –
existing rocks prevent erosion by stabilizing the shoreline
Practice responsible boating:
o
Choose a boat the fits the size of the lake
o
Avoid spilling gas - fix all leaks
o
Watch your wake – large wakes cause erosion and
damage wildlife habitat
o
Know and obey boating laws