 |
Earth's Water:
|
If people had to pick their favorite water body
(vote for yours in our opinion survey), they'd probably
choose a crystal-clear lake nestled in the mountains (my opinion, or
course!). Not all lakes are clear or are near mountains, though. The
world is full of lakes of all types and sizes.
A lake really is just another component of Earth's surface water. A lake is where surface-water runoff (and maybe some ground-water seepage) have accumulated in a low spot, relative to the surrounding countryside. It's not that the water that forms lakes get trapped, but that the water entering a lake comes in faster than it can escape, either via outflow in a river, seepage into the ground, or by evaporation.
A reservoir is the same thing as a lake in many peoples' minds. But, in fact, a reservoir is a manmade lake that is created when a dam is built on a river. River water backs up behind the dam creating a reservoir.
Here's a question for you: when a beaver dams a creek, is the pond that it creates a lake or a reservoir?
The Earth has a tremendous variety of freshwater lakes, from fishing ponds
to Lake Superior (the world's largest), to many reservoirs. Most lakes
contain fresh water, but some, especially those where
water cannot escape via a river, can be salty. In fact, some
lakes, such as the Great Salt Lake, are saltier
than the oceans. Most lakes support a lot of aquatic life, but
the Dead Sea isn't called "Dead" for nothing -- it is
too salty for aquatic life! Lakes formed by the erosive force of ancient
glaciers, such as the Great
Lakes, can be thousands of feet deep. Some very large
lakes may be only a few dozen feet deep -- Lake Pontchartrain in
Louisiana has a maximum depth of only about 15 feet.
Some of the salty lakes were formed in ancient times when they were connected to seas and when rainfall may have been heavier. These lakes have been shrinking since the last ice age. The ancient Lake Bonneville in the United States was once as big as Lake Michigan, and the Great Salt Lake was once about 14 times as large as it is now.
Sources and more information • Lake Tahoe Data Clearinghouse - Information and data pertaining to Lake Tahoe
• Crater Lake Data Clearinghouse - Information and data pertaining to Crater Lake
• Great Lakes Science
• Great Salt Lake, Utah
The water cycle: Freshwater storage
U.S. Department of the Interior | U.S. Geological Survey
URL: http://ga.water.usgs.gov/edu//earthlakes.html
Page Contact Information: Howard Perlman
Page Last Modified: Wednesday, 13-Aug-2008 07:18:52 EDT
Vote for your