Environmental Engineering Reference
In-Depth Information
the metabolic rates of aquatic organisms, and the sensitivity of organisms to
toxic wastes, parasites, and diseases. Causes of temperature change include
weather, removal of shading stream-bank vegetation, impoundments (a body
of water confined by a barrier, such as a dam), discharge of cooling water,
urban stormwater, and groundwater inflows to the stream.
useful Conversions
20°C = 68°F
0°C = 32°F
100°C = 212°F
Sampling and equipment Considerations
Temperature in a stream varies with width and depth, and the temperature of
well-sunned portions of a stream can be significantly higher than the shaded
portion of the water on a sunny day. In a small stream, the temperature will
be relatively constant as long as the stream is uniformly in sun or shade. In
a large stream, temperature can vary considerably with width and depth,
regardless of shade. If safe to do so, temperature measurements should be col-
lected at varying depths and across the surface of the stream to obtain vertical
and horizontal temperature profiles. This can be done at each site at least once
to determine the necessity of collecting a profile during each sampling visit.
Temperature should be measured at the same place every time. Temperature
is measured in the stream with a thermometer or a meter. Alcohol-filled ther-
mometers are preferred over mercury-filled ones because they are less haz-
ardous if broken. Armored thermometers for field use can withstand more
abuse than unprotected glass thermometers and are worth the additional
expense. Meters for other tests, such as pH (acidity) or dissolved oxygen, also
measure temperature and can be used instead of a thermometer.
Hardness
Water hardness refers primarily to the amount of dissolved calcium and
magnesium in the water and their effects on scaling, corrosion, and soap.
With hard water, it is difficult to produce a soap lather. Hard waters leave
spots on glasses, a film on laundry and hair, and crusty deposits on bath-
room fixtures. The presence of hardness in water supplies contributes to
taste, odor, color, or turbidity, but water hardness has no health significance
(Hauser, 2002). Calcium and magnesium enter water mainly by leaching
of rocks. Calcium is the most abundant dissolved cationic constituent of
