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Rivers? Streams? Creeks? They are all names for water flowing on the
Earth's surface. As far as the Water Science site is concerned, they
are pretty much interchangeable. I tend to think of creeks as the
smallest of the three, with streams being in the middle, and rivers
being the largest.
What is a river?A river is nothing more than surface water
finding its way over land from a higher altitude to a
lower altitude, all due to gravity. When rain falls on the land, it
either seeps into the ground or becomes runoff,
which flows downhill into rivers and lakes, on its journey towards the seas. In most landscapes the land
is not perfectly flat -- it slopes downhill in some direction. Flowing water finds
its way downhill initially as small
creeks. As small creeks flow downhill they merge to form larger streams
and rivers. Rivers eventually end up flowing into
the oceans. If water flows to a place that is
surrounded by higher land on all sides, a
lake will form. If man has
built a dam to hinder a river's flow, the lake that forms is a
reservoir.
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Where does the water come from? |
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The water in a river doesn't all come from surface runoff. Rain
falling on the land also seeps into the earth to form
ground water. At a certain depth below
the land surface, called the water table
,
the ground becomes saturated with water.
If a river bank
happens to cut into this saturated layer, as most rivers do, then water will seep out
of the ground into the river. Ground-water seepage can sometimes
be seen when a road is built
through water-bearing layers
 ,
and even on a driveway
!
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| Look at the diagram below. The earth below the water table, the aquifer (the purple area), is saturated, whereas the earth above (the pink area) is not. The top layer (unsaturated soil/rock material) is usually wet, but not totally saturated. Saturated, water-bearing materials often exist in horizontal layers beneath the land surface. Since rivers, in time, may cut vertically into the ground as they flow (as the river cuts into the purple section in the diagram), the water-bearing layers of rock can become exposed on the river banks. Thus, some of the water in rivers is attributed to flow coming out of the banks. This is why even during droughts there is usually some water in streams. |
Rivers and the landscape
Rivers and sediment
River lengths
Surf your watershed (EPA)
Earth's water
Water Science home page
USGS Water ResourcesThe URL for this page is http://ga.water.usgs.gov/edu/earthrivers.html Comments? Contact Howard Perlman Last Modified: May 28, 2003 |
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