Harbor Watch, a Program of Earthplace Report on Norwalk Harbor Juvenile Benthic Marine Fish May through October 2014
View water quality report for the Silvermine River and the lower Norwalk River storm drains - May through August 2014
View water quality report for the Silvermine River and the lower Norwalk River storm drains - May through August 2013
View water quality reports (Upper Watershed) for the months of Sept 2011 through March 2012
View water quality reports for the months of October 2011 through April 2012
View water quality reports for the months of May 2011 through September 2011
View water quality readings for the months of October 2010 through April 2011
View water quality readings for the months of May 2010 through September 2010
View water quality readings for the months of October 2009 through April 2010
Dick
Harris - Water Quality Conditions in the Norwalk River May
2009 thru September 2009
Dick
Harris - Water Quality Conditions in the Silvermine / Lower
Norwalk River Summer 2009
Dick
Harris - Water Quality Conditions in the Norwalk River Winter
2009 thru Spring 2009
View
water quality readings for the months of May 2008 through
Sept. 2008
View
water quality readings for the months of October 2007 through
April 2008
View
water quality readings for the months of May through September
2007
View
water quality readings for the month of August 2004
Historic
Readings:
The
Trends at Perry Avenue...
The
best published record of the water quality in the Norwalk
River comes from a 17-year series of sample measurements recorded
by the USGS at near the Perry Avenue bridge in Norwalk. Perhaps
the most important component of riverwater is dissolved
oxygen. Fish, insect larvae, and all other forms
of animal life in the river die if the oxygen is depleted.
The typical amount of oxygen in riverwater is about 10-12
mg/l (milligrams per liter), and Connecticut requires the
amount of oxygen to remain above 5 mg/l except in the most
extreme droughts. In a 17-year series of data collected
by the USGS near the Perry Avenue bridge in Norwalk, the dissolved
oxygen had an average value of 11.7, and a minimum reading
of 6.04. A slight downward trend may be due to the fact that
in recent years a larger percentage of the measurements were
made in the summertime when the oxygen levels are low.
Any discussion of Connecticut's riverwater is officially divided
into five distinct categories:
AA |
Water
for public reservoirs |
A |
Other
drinkable river water |
B |
Undrinkable
but satisfactory |
C |
Unsatisfactory |
D |
Very
unsatisfactory |
How
can we decide whether a river's water is "good"? The
most direct approach would be to drink a large quantity of
the water and discover any consequences a short time later
(but don't try that!) Two variations on this approach
are used for actual tests of riverwater:
The first method is to start with a list of waterborne
materials that are known to be good or bad, and then, rather
than drinking the water sample, analyze it scientifically
to determine how much of these good and bad ingredients it
contains. The results of these tests can give a wealth
of information about the dangers posed by the water and the
trends over time in a positive or negative direction.
The second method is to examine the health of all the
tiny river-dwelling animals that "drink" the water continuously.
If they are numerous and thriving, it tells us that certain
minimal conditions must be present in the water. If
the river is polluted by a series of severe episodes (like
the weekly discharge of a load of poisons), the tiny animals
might all be dead, but most water samples would indicate an
excellent water quality (except during the brief episodes).
Method
1: Water Samples
The
United States Geological Survey (USGS) tests water samples
from many of the Nation's rivers on a regular basis.
The most important results are published once a month, and
the entire set of results is released to the public annually.
For the Norwalk River, the USGS has performed tests approximately
once per month since 1980 at a site near the Perry Avenue
bridge in Norwalk. The entire set of USGS data is held
in an archival database (STORE-T) administered by the US Environmental
Protection Agency (EPA). The archival data from the
EPA has been combined here with the more recent data from
the USGS's Connecticut website to give a complete picture
of the sampling data.
Many other organizations beside the USGS have made important
measurements of the water quality of the Norwalk River.
One organization that is particularly active in this field
is the Nature Center for Environmental Activities in Westport.
It has earned governmental certification for its rigorous
quality control standards and has begun an ambitious program
to sample the watershed at many points to get a map of the
water quality. We would be happy to publicize that data
or any other significant datasets that have been collected
within the Norwalk River watershed. If you have any
such data, please contact
us. Thanks!
1.
Important "basic" components
The
following components of riverwater can be measured relatively
easily by students or "volunteer monitors" and play a vital
role in determining a river's condition.
OXYGEN. Fish, insects,
and all other forms of animal life require oxygen to survive.
The amount of oxygen dissolved in a river's water is one of
the most important indicators of the river's overall health.
It can be expressed as a total amount
of dissolved oxygen per liter of water or as a percentage
of the maximum amount that can be dissolved in still water
at the ambient temperature. Agitated water can have percentages
over 100%, as can water with active chemical or biological
processes.
NITROGEN. When excess
nitrogen pours from a river into a confined region such as
Long Island Sound, it often creates algae blooms which deplete
the water's oxygen and kills aquatic life. Consequently,
this element is watched very closely. It occurs in three
main forms in riverwater: nitrites, nitrates, and ammonia,
and it can be separated into organic and inorganic components.
The USGS currently measures (or used to measure): total
nitrite, dissolved nitrite, total
nitrite plus nitrate, dissolved nitrite
plus nitrate, dissolved ammonia,
total ammonia plus organic, and dissolved
ammonia plus organic.
PHOSPHOROUS.
Excess phosphorous produces rapid plant growth which can choke
off waterways. The following variables have been recorded:
total phosphorous, dissolved
phosphorous, and dissolved ortho phosphorous.
pH. The concentration
of hydrogen ion activity (essentially the opposite of acidity)
dictates a solution's pH. Neutral water has a pH value
of 7.0, and the value decreases as the water's acidity increases.
Every aquatic organism has a certain range of pH values that
it can tolerate. Considering all of the problems with
acid rain, many people are surprised to learn that our rivers
tend to be more base than acidic. The variable comes in two
forms: pH (Field Measurement)
and pH (Lab Measurement).
ALKALINITY. A
water's alkalinity refers to its capacity to neutralize acids.
Since this acid "buffering" capacity is often produced by
bicarbonates in the water, the alkalinity
parameter is related to the bicarbonates,
and the carbonates. Three other carbon
measurements are also made: total organic
carbon, dissolved organic carbon,
and organic suspended carbon.
CHLORIDE. The presence
of excess chloride in riverwater can
indicate a source of salt (perhaps roadsalt) entering the
river. A closely related element, but important mainly in
drinking water, is fluoride.
2.
Other basic measurements
The
following measurements are usually collected whenever a water
analysis is made, though they do not involve specific materials
in the water. Three other parameters, the color, taste, and
odor of the water, are mentioned in Connecticut's water-quality
regulations but are not quantified in the USGS data.
FLOW RATE. Officially
listed as instantaneous discharge,
this is the amount of water flowing past a fixed point on
the shoreline per unit of time. The flow rate in South Wilton
is recorded daily by an automatic measurement device, and
a graph of that data for any calendar period can be obtained
from this site.
TEMPERATURE.
Both water temperature and air
temperature are recorded.
ELECTRICAL CONDUCTANCE.
Officially listed as specific conductance,
this indicates the presence of salts and other impurities
in the water.
TURBIDITY. The
opaqueness or non-clarity of the water. Since opaqueness is
often caused by suspended solids, the turbidity
parameter is related to suspended sediments,
fine suspended sediments, total
solids, and dissolved solids.
3.
Advanced measurements.
The
following measurements are not usually included in a "basic"
set, suitable to be done by students or volunteers. Many of
them require complex equipment or intricate procedures.
BACTERIA. Bacteria
give a warning of possibly dangerous biological contaminents
in the water. These measurements are exceedingly important
but are difficult to perform reliably. The following bacteria
counts are provided by the USGS: enterococci,
fecal coliform, and fecal
streptococci.
METALS. Many different
metals can create medical problems if they're ingested even
in small amounts. Consequently, the USGS measures and reports
trace quantities of all of the following elements:
aluminum, antimony,
barium, beryllium,
cadmium, calcium,
chromium, cobalt,
copper, iron,
lead, magnesium,
manganese, molybdenum,
nickel, potassium,
silver, sodium,
uranium, and zinc.
NON-METALS. The
following components of the water are also measured:
silica, sulfate,
total hardness, and cal
hardness.
Method
2: Aquatic Animals
The
small animals that live in streambeds, often clinging to the
bottom surfaces of rocks, are called benthic macroinvertebrates.
"Benthic" refers to the location, at the bottom of a body
of water, and "macroinvertebrates" refers to simple organisms
that are large enough to be seen by the unaided eye.
Some of these organisms are very sensitive to pollution, while
others are only moderately sensitive and a third group is
largely insensitive. When a survey is made of these creatures,
the best result is to find a large variety of species including
many of the pollution-sensitive types. The actual count of
the individual specimens is not nearly as important as the
diversity.
Back in 1982, a detailed report was published giving the results
of a benthic macroinvertebrate study on the Norwalk River
["Derivation of Site Specific Water Quality Criteria for the
Norwalk River at Georgetown, Ct." by L.E. Dunbar and E. Pizzuto].
It listed 38 different varieties (taxa) that were observed,
and several of them were pollution sensitive. Other studies
have generally produced good or borderline-good results. A
new study is currently in preparation, and we hope to publish
the results when they are available.
So??
Is it Good or Bad?
Connecticut's
riverwater is officially divided into five distinct categories:
AA |
Water
for public reservoirs |
A |
Other
drinkable river water |
B |
Undrinkable
but satisfactory |
C |
Unsatisfactory |
D |
Very
unsatisfactory |
The
water at the Perry Avenue bridge should fall into category
B. This quality of riverwater is defined in a CT-DEP document,
Water Quality Standards (effective April 8, 1997),
which places requirements on 13 different parameters. These
requirements can be characterized (in part) as follows:
1. |
Aesthetics |
Good
to excellent. |
2. |
Dissolved Oxygen |
Not
less than 5 mg/l at any time. |
3. |
Sludge |
Essentially
none. |
4. |
Color |
Essentially
no visible discoloration. |
5. |
Suspended Solids |
None
which would impair the most sensitive uses. |
6. |
Silt and Sand |
Normal
roadsand is allowed "provided all reasonable controls
or Best Management Practices are used." |
7. |
Turbidity |
Shall
not exceed 5 NTU over ambient levels. |
8. |
Bacteria |
Fecal
coliform shall not exceed a geometric mean of 200 colonies
per 100 ml in any group of samples nor shall 10% of
the samples exceed 400 colonies per 100 ml. There are
also limits on enterococci in established bathing waters. |
9. |
Taste and Odor |
None
that impair the water's uses. |
10. |
pH |
6.5
to 8.0 |
11. |
Temperature |
No
increases that impair water's use. |
12. |
Chemicals |
None
that impair the water's use. |
13. |
Benthic Invert. |
Water
quality shall be sufficient to sustain a diverse macroinvertebrate
community of indigenous species. |
The
most troublesome entry on this list is item 8, which specifies
the limits on bacteria. Comparing these limits with the
fecal coliform measured on the Norwalk
River, it seems that the river fails this test. Item 10,
pH, is generally in the specified
range, and item 2, dissolved oxygen,
is always above the required 5.0. (Lower DO values were
measured at some points on the river during a severe drought
in 1995, but the regulations allow for bad readings in major
droughts.)
Is
it Getting Better or Worse?
In
the area of bacteria, the data seem
to show an improvement around 1990 followed by a worsening
in the later 1990's. This subject is currently being addressed
very agressively by several organizations, and we should have
more definite information when the current studies are complete.
In the areas of nitrogen and phosphorous
(which are potentially damaging to the waters of Long Island
Sound but are not mentioned in the official class-B criteria)
there has been a statistically significant improvement,
at least from 1980 to 1992. This is documented in a USGS report
on 14 Connecticut rivers. The Norwalk River is the only one
that has a significant improvement in all of the studied variables.
Two modern wastewater-treatment plants went online along the
Norwalk River in the mid-1990's (in Ridgefield and Georgetown),
so the apparent improvement that extends into the 1990's is
probably real, though small.
By far the most conspicuous trend in the data lies in the
trace metal measurements (lead, copper,
and many others), where a dramatic improvement has occurred,
but starting from extremely bad initial levels. The river's
chloride and electrical
conductance measurements seem to be increasing, indicating
possible salt problems in the river.
View
water quality readings for the months of October 2007 through
April 2008
View
water quality readings for the months of May through September
2007
View
water quality readings for the month of August 2004
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