Drinking Water Monitoring - The Drinking Water - page 187

TAble 10.2
Fecal Coliform Bacteria per 100 mL of Water

Desirable Permissible Type of Water Use

0 0 Potable and well water (for drinking)

<200 <1000 Primary contact water (for swimming)

<1000 <5000 Secondary contact water (for boating and fishing)

1. To identify whether waters are meeting designated uses . All states have
established specific criteria (limits on pollutants) identifying what
concentrations of chemical pollutants are allowable in their waters.
When chemical pollutants exceed maximum or minimum allowable
concentrations, waters may no longer be able to support the bene-
ficial uses—such as fishing, swimming, and drinking—for which
they have been designated (see Table 10.2 ). Designated or intended
uses and the specific criteria that protect them (along with antideg-
radation statements that say waters should not be allowed to deterio-
rate below existing or anticipated uses) together form water quality
standards. State water quality professionals assess water quality
by comparing the concentrations of chemical pollutants found in
streams to the criteria in the state's standards and judge whether
or not streams are meeting their designated uses. Water quality
monitoring, however, might be inadequate for determining whether
aquatic life needs are being met in a stream. Whereas some constitu-
ents (such as dissolved oxygen and temperature) are important to
maintaining healthy fish and aquatic insect populations, other fac-
tors (such as the physical structure of the stream and the condition
of the habitat) play an equal or greater role. Biological monitoring
methods are generally better suited to determining whether or not
aquatic life is supported.

2. To identify specific pollutants and sources of pollution . Water quality mon-
itoring helps link sources of pollution to stream quality problems
because it identifies specific problem pollutants. Because certain
activities tend to generate certain pollutants (bacteria and nutrients
are more likely to come from an animal feedlot than an automotive
repair shop), a tentative link to what would warrant further investi-
gation or monitoring can be formed.

3. To determine trends . Chemical constituents that are properly moni-
tored (i.e., using consistent time of day and on a regular basis using
consistent methods) can be analyzed for trends over time.

4. To screen for impairment . Finding excessive levels of one or more
chemical constituents can serve as an early warning for potential
pollution problems.