bu Hilary Stevens and Liam Pott
The Androscoggin River water quality news is good. Last summer,
the Council conducted a water quality testing program for temperature,
dissolved oxygen, suspended solids, and E. Coli bacteria on the
Androscoggin River from Gorham, N.H., to Brunswick, Maine.
Although the water was warmer than usual, it was not warm enough
to cause any serious problems. The temperature of rivers naturally
changes during a year. Snowmelt in the spring causes high flows
of very cold water, while the summer and fall sun warm the water.
Fish and other species have adapted to this cycle, and have
trouble with too much variation. Very warm water is particularly
difficult on fish. They are cold-blooded, and they have trouble
regulating their metabolism if their body temperature gets too
high.
To compound the problem, water chemistry changes with temperature.
The amount of oxygen that will dissolve in the water decreases
as the water gets warmer, just like soda or beer will go flat
if left warm. Just when a fish needs more oxygen because of the
higher metabolic rate, there is less
available. Our measurements show that this year was warmer than
usual.
The oxygen measurements show that there is enough oxygen in
most areas, most of the time.
The dissolved oxygen in the water changes when temperature
changes. The water also has to be mixed up to keep oxygen in the
water. This mixing happens when water runs over rocks or a dam,
but when water is still, such as in a lake or behind a large dam,
it doesn't get mixed enough.
Water organisms need oxygen just like land organisms. One area
of the river fell below the minimum standard goal in July, when
the air and water are warmest. Some other areas upriver fell below
their section goals, but the level of oxygen was above the level
considered the lowest acceptable in Maine.
The Androscoggin River has very little suspended material in
most areas. The standard is exceeded on one sample, but for most
of the time, this is not a problem.
In addition to dissolved gases, water also carries a lot of
particles with it. Water that carries a lot of suspended particles
can begin to look clouded and brown. Usually, that happens when
something near the river is causing a lot of erosion. The water
is hard to see through and hard to breath.
Fish and other animals that hunt by sight can have difficulty
finding enough food. Also, fish have trouble with their gills
if there is too much matter in the water, just like people can't
breathe very well in smoky or dusty air.
This year's measurements for E. Coli are much lower than previous
measurements. As with any natural system, rivers contain a wide
variety of bacteria. Most fish and animals that live in and around
the water have natural defenses to these bacteria.
People, however, are more susceptible to diseases from exposure to them, either by drinking the water or swimming in it. In particular, the E. Coli bacteria can cause infections and other illnesses.
It usually enters the waterway from untreated sewage or pet
and livestock wastes. The bacteria only live a few days in water,
so the problem is worse close to the source, or right after a
storm that brings waste to the water.
There are several ways to measure the bacteria to try to determine
if there is a risk to human health. The first standard is in instantaneous
maximum - that is, the bacteria count should never exceed this
level. The bacteria count is usually highest right after a big
storm, so that's when it is most
likely to reach this max.
The other standard is a geometric mean. This measure takes
into account the range of measurements, that whether or not it
has a peak value that is too high, the entire range of counts
is too high.
Our measurements this year never exceeded the instantaneous
value. One site is very close to the geometric mean max, which
means that there is probably some slow, steady source of bacteria
in the area.
Last year's water quality monitoring effort was successful
on two counts. The record of water quality indicators was expanded,
and we can say that water quality is in pretty good shape.
There are a few points where water quality standards are exceeded,
but never for more than one week's measurement. In some cases,
the data look better than last time: E.Coli counts are lower overall,
and dissolved oxygen levels are good despite high temperatures.
The river is in reasonably good health now, and if current trends continue, the Androscoggin River will continue as a healthy habitat and resource in years to come.
Hilary Stevens and Liam Pott worked as summer interns for the Council. They are recent graduates of, respectively, the Yale School of Forestry and Princeton.