| What Is A Watershed?
A
watershed describes an area of land that contains a common set of streams
and rivers that all drain into a single larger body of water, such as a
larger river, a lake or an ocean. For example, the Mississippi River watershed
is an enormous watershed. All the tributaries to the Mississippi that collect
rainwater eventually drain into the Mississippi, which eventually drains
into the Gulf of Mexico. Rainwater that falls on more than half of the
United States subsequently drains into the Mississippi.
 A
watershed can cover a small or large land area. In the St. Louis vicinity,
for instance, the Meramec River is a small river draining a relatively
small amount of land. Small watersheds are usually part of larger watersheds.
The Meramec River watershed, which is supplied by even smaller watersheds
from dozens of streams, drains into the Mississippi River. All the streams
flowing into small rivers, larger rivers, and eventually into the ocean,
form an interconnecting network of waterways.
Not only does water run into the streams and rivers from
the surface of a watershed, but water also filters through the soil, and
some of this water eventually drains into the same streams and rivers.
These two processes, surface runoff
and
infiltration are important for a number of reasons.
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| A Stream in Washington
State |
The network of streams and rivers that drain our watershed
and carry water pollution ultimately empty into larger bodies of water,
such as lakes and oceans. As the larger rivers carrying water pollution
from the land flow into lakes and oceans, all of the pollution that was
in the rivers now is concentrated into these other bodies of water. The
oceans of the world become the final resting place for tons of pollution.
Through our watersheds, pollution is distributed far away from its original
source. And oviously, polluted water affects water quality.
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Botanical Garden
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