- Frozenwaterfoundinicebergshasnotbeenfoundtobeareliablewatersource. Glacier
runoff is a source for surface water.
Introduction
While water may seem limitless and everywhere – after all, you can turn your faucet and out
it comes, without appearing to dry up – in fact, in the United States it is a limited resource,
and in many parts of the world, even scarce. Add to this the necessity of having water
without pollution and you can see that unpolluted water is even harder to find (Figure
25.8).
Waterpollutionisthecontaminationofwaterbodiesbycontaminants,mostlyanthropogenic,
and causing a harmful effect on living organisms. As you explore in this lesson how water
pollution affects living things, you will see the urgency in preventing water pollution and
discover ways to save water. Perhaps you will be inspired to think of how your household,
community, and even world can be a model to others to not take clean water for granted!
Sources of Water Pollution
Although natural phenomena such as storms, algal blooms, volcanoes, and earthquakes can
cause major changes in water quality, human-caused contaminants have a much greater
impact on the quality of the water supply. Water is considered polluted either when it does
not support a human use (like clean drinking water) or undergoes a major change in its
ability to support the ecological communities it serves.
The primary sources of water pollution can be grouped into two categories, depending on
the point of origin:
A.Point source pollutionrefers to contaminants that enter a waterway or water body
through a single site. Examples of this includes discharge (also called effluent) of either
untreated sewage or wastewater from a sewage treatment plant, industrial effluent,
leaking underground tanks, or any other discrete sources of nutrients, toxins, or waste.
B.Nonpoint source pollutionrefers to contamination that does not originate from a
single point source, but is often a cumulative effect of small amounts of contaminants
(such as nutrients, toxins, or wastes) gathered from a large area. Examples of this in-
clude runoff in rainwater of soil, fertilizers (nutrients) or pesticides from an agricultural
field, soil from forested areas that have been logged, toxins or waste from construction
or mining sites, and even fertilizers or pesticides from your own backyard!
Specific contaminants causing water pollution include a wide variety of chemicals, and
pathogens (disease-causing substances). While many of the chemicals and substances that