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.
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.
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!
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.
While you're here .. care to vote for your favorite water body?
Investigate the water cycle: streamflow (in many languages!)
Rivers and sediment
River lengths
Streamflow patterns
Measuring streamflow
Floods Q&A
A water monitoring site
U.S. Department of the Interior | U.S. Geological Survey
URL: http://ga.water.usgs.gov/edu/earthrivers.html
Page Contact Information: Howard Perlman
Page Last Modified: Monday, 28-Aug-2006 14:56:21 EDT
