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Q: The hydrologic cycle, rivers, streams, and lakes. ( Answered,   2 Comments )
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 Subject: The hydrologic cycle, rivers, streams, and lakes. Category: Science Asked by: chuckie1-ga List Price: \$15.00 Posted: 12 Apr 2003 22:42 PDT Expires: 12 May 2003 22:42 PDT Question ID: 189832
 ```How does a river system change from upstream (i.e. in the mountains) to downstream?Why do streams meander? How in meandering related to the velocity of water flow within a meandering stream?```
 ```Hi Chuckie1, I tried to answer your query point by point. Simply press the "Shift" key before clicking on a link so it will open a new window or right-click on the link and choose "Open in New Window" for your convenience. "How does a river system change from upstream (i.e. in the mountains) to downstream?" When you say upstream, it means the direction that is contrary to the flow of a river or stream. All flowing body of water flow in one direction only and as such, none can flow against its natural direction. As an example, you cannot find a waterfall flowing up or a stream or river flowing up a mountain. Given these, I take your question as, "How does water flow down from the mountain to the river and eventually, to the sea?" Water don't just appear high up in the mountain so there should be a source. Here's a simple explanation of how it starts: Water from the ocean is vaporized by the heat of the sun. This is called evaporation. The vaporized water condense high up in the sky to form clouds. When too much water vapors are added to the cloud, it becomes heavy and saturated. Soon, water falls down as rain. Rain will fall down the mountain which will fall down as streams which become bigger and merge into a river, which eventually flows out to the sea. Then the cycle repeats again. Here are links to help you better understand this cycle: U.S. Environmental Protection Agency THE WATER CYCLE http://www.epa.gov/OGWDW/kids/cycle.html The University of Washington THE WATER CYCLE http://www-k12.atmos.washington.edu/k12/pilot/water_cycle/grabber2.html KidZone THE WATER CYCLE http://www.kidzone.ws/water/ "Why do streams meander?" There are many reasons why streams meander or flow in a winding course. One cause is diversion. No matter how straight water flows down a mountain, it will eventually encounter a rock, stick, or any other body that will cause it to become diverted from its original path. Other reasons are the angle of the surface where it flows, the speed of flow, etc. The hardness or softness of a surface is also a factor. Water will erode softer surfaces than hard ones and will eventually form a natural channel where water water will flow. Streams tend to meander naturally and vary in width, depth and velocity based on the surface on which it flows. Older, flatter streams meander more than younger, steeper streams. Here are some links that can help you understand this subject: Conservation Commission of Missouri UNDERSTANDING STREAMS http://www.conservation.state.mo.us/fish/streams/under/ Beall High School Science Classes INVESTIGATION : A MINI-VIEW OF A RIVER http://www.geocities.com/bhwater2000/StreamInv.html "How is meandering related to the velocity of water flow within a meandering stream?" I believe this has been covered in the links above. As explained before, water will erode softer surfaces than hard ones and will eventually form a natural channel where water water will flow. This means that the faster the rate of flow (velocity ) water, the faster it erodes a surface. So you can imagine a surface where water flows exactly between a soft surface and a hard surface -- both will be eroded, but since the rate of erosion will be faster on the softer side, water will eventually veer away from the harder surface. Here are more links to assist you: National Park Service (NPS) on the Web CHANGING LANDFORMS IN MIDSTREAM http://www.nps.gov/brca/Geodetect/Landfroms/stream%20channels.htm You can still fine additional references from the last three links below. Search strategy: "water cycle" ://www.google.com/search?q=%22water+cycle%22&cat=&hl=en "streams meander" http://www.fish.washington.edu/naturemapping/water/1qualnv.html meandering "water flow" streams ://www.google.com/search?q=meandering+%22water+flow%22+streams&hl=en&lr=&ie=UTF-8&oe=UTF-8 I hope this helps you. Should you have any comments/questions, please feel free to post your clarification before rating this and I'll attend to you as soon as possible. Thanks for asking. Best regards, Feilong```
 ```When felong said water in a body of water can flow in one direction only, I was challanged. Whirlpools occur and tide direction change does not occur at the same instant in all parts of a body of water. Also the wind can cause surface water to move in a different (even opposite direction) to water at mid depth. This is not important to the question or the answer which is otherwise excellent. Neil```
 ```Meandering is not thought to be caused by differences in resistance to erosion. Meanders occur in regions where the stream's velocity is insufficient to keep its sediment load in motion and it begins depositing coarser material. At any point where astream is following a curved path, the water on the inside of the bend is moving slower than the water on the outside, so deposition of features called "point bars" is occurring on the inside of the curve at the same time that the water on the outside of the curve is eroding the bank. Thus through time, the curve becomes increasingly sharp, giving rise to the typical "snakey" shape of a meandering stream. As point in fact, a meandering stream is almost always cutting back and forth across its own floodplain, eroding the stream deposits that it, itself, laid sometime earlier in its history. For more information see http://daac.gsfc.nasa.gov/DAAC_DOCS/geomorphology/GEO_4/GEO_CHAPTER_4.HTML http://www.gcrio.org/geo/channel.html http://www.geog.ouc.bc.ca/physgeog/contents/11j.html```