What is a River System?
Every river is part of a larger system—a watershed, which
is the land drained by a river and its tributaries. Rivers are
large natural streams of water flowing in channels and emptying
into larger bodies of water. This diagram shows some common characteristics
of a river system. Every river is different, however, so not all
rivers may look exactly like this illustration.
The river source, also called the headwaters, is the beginning
of a river. Often located in mountains, the source may be fed
by an underground spring, or by runoff from rain, snowmelt,
or glacial melt.
A tributary is a smaller stream or river that joins a larger or
The main river is the primary channel and course of a river.
A fully-developed floodplain is relatively flat land stretching
from either side of a river, which may flood during heavy
rain or snowmelt. Built of materials deposited by a river,
floodplain soil is often rich in nutrients and ideal for
A meander is a loop in a river channel. A meandering river
winds back and forth, rather than following a straight course.
Upstream is in the direction of or nearer to the source
of a river
Wetlands are low-lying areas saturated with water for long enough
periods to support vegetation adapted to wet conditions. Wetlands
help maintain river quality by filtering out pollutants and sediments,
and regulating nutrient flow.
The river mouth is the place where a river flows into a larger
body of water, such as another river, a lake, or an ocean.
A watershed boundary, also called a drainage
divide, marks the
outer-most limit of a watershed. A watershed is a tract of land
drained by a river and its tributaries. Anything that affects
a watershed may eventually impact its tributaries and river as
well as the water body at the mouth of the river. People's actions
within a watershed can affect the overall quality of its rivers.
Downstream is in the direction fo or nearer to the mouth of a
What is a River System? (Adobe PDF document)