Water is vital to all life on Earth. The
water in a stream sustains aquatic organisms
such as fish and insects as well as organisms
that live throughout the entire watershed. That
includes humans. Entire cities may depend on
the water in a single medium-sized river. Water
is used for drinking, washing, watering and
irrigation, and many commercial and industrial
processes. The same water transports the
effluent of wastewater treatment.
Because water is vital to life, it is
accurate to say that poor water quality equals
a poorer quality of life.