INTRODUCTION - Water Quality Engineering in Natural Systems - page 6

Point sources are most easily controlled since they
have identifiable discharge locations; the quality of
these discharges can usually be monitored, and appro-
priate treatment can be preformed prior to discharge.
In contrast to point sources, nonpoint sources are not
easily identifiable and the discharges from these sources
cannot be easily monitored. As a consequence, control
of nonpoint sources of pollution is usually accomplished
by instituting best management practices at the water-
shed level. Ideally, watershed-scale fate and transport
models can be used to simulate the movement and
attenuation of pollutants from their terrestrial source to
the receiving water body, and such modeling can be
helpful in establishing the link between watershed con-
trols and water quality in the receiving water body.

once a water body is polluted, then there is an added
dimension of remediation. The design of an effective
remediation scheme requires a fundamental under-
standing of the fate and transport of pollutants in the
water body, and an understanding of how the pollutant
will respond to various modifications within the water
body. Any effective remediation approach must be
accompanied by pollutant source controls that are con-
sistent with the water-quality requirements being met.
This topic presents the tools and concepts required
for water-quality control in natural waters. These include
an understanding of water-quality criteria, the funda-
mentals of fate and transport in natural waters, estima-
tion of pollutant loading, and the design of remediation
systems.