Why do rivers have their source at top of hills and mountains?

Question

as opposed to starting out of springs or other at sea level. I cannot understand how enough water goes to the top of hills to create rivers. It is not melting snow because the rivers continue in summer. Something scientific must make the water rise underground to form the springs.

Answer 1

Because the water flows down hill due to gravity, forming a river or stream.

Answer 2

The answer, very simply is rainfall. In the UK (and elsewhere) the highest rainfall is in mountainous areas. Once it has fallen, there are three possible routes for the water:

evaporation

absorption into the soil and then rocks

run off

It is the last of these - where the water simply runs away down hill on the surface that causes streams and then rivers to form. They start off as small trickles, but additions on the way down soon swell the flow. Even some of the water which has been absorbed into the soil will slowly trickle out into the water flow. This is not necessarily a fast process and hence the water continues to flow even when there has not been much rain. You also have to remember that rivers collect their water from very large areas, which contain a lot of water.

Answer 3

In order for water to flow like a river it needs to go from a higher elevation to a lower elevation using gravity, otherwise you have a lake. But rivers don't always start in a mountain or a hill. Some start out at a lake at higher elevation, but not a mountain or a hill, and travel to a lower elevation.

And travel to the source of rivers that do start out in the mountains, and as the summer progresses the river starts to dry up starting at the source which could be the snow pack. I know of several rivers in my area that are dry at the source in the middle of summer but if i travel down the bed i start to encounter more feeder streams and the quantity and volume of these streams usually increase further down the river i go.

Rivers are part of the groundwater system, eg the closer to the river one gets the closer to the ground surface the water table gets. There wouldn't be a river if the water table was below the ground surface.

Answer 4

The Hydrological Cycle

(also known as the water cycle) is the journey water takes as it circulates from the land to the sky and back again.



The sun's heat provides energy to evaporate water from the earth's surface (oceans, lakes, etc.). Plants also lose water to the air - this is called transpiration. The water vapour eventually condenses, forming tiny droplets in clouds.



When the clouds meet cool air over land, precipitation (rain, sleet, or snow) is triggered, and water returns to the land (or sea). Some of the precipitation soaks into the ground. Some of the underground water is trapped between rock or clay layers - this is called groundwater. But most of the water flows downhill as runoff (above ground or underground), eventually returning to the seas as slightly salty water.



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I hope this is helpful.

Answer 5

Good Lord, have you never heard of rain.



Mountains make rain by forcing air up over them - air rises, cools and drops its moisture.



Therefore mountains are generally much more rained on (or snowed on) than lowlands.



The Amazon is fed from the high Andes catchment.



The Nile from Ethiopian highlands



The Mississippi from the Rockies.



Rain Rain Rain - not springs.

Answer 6

Water tables tend to follow the elevations of the land. Remember that not all rock has the same permeability; thus, water is trapped above some layers of rock.

http://coastgis.marsci.uga.edu/summit/images/aquiferdiag.jpg



http://www.waterencyclopedia.com/images/wsci_02_img0238.jpg



http://www.maine.gov/doc/nrimc/mgs/explore/water/facts/aq-01.gif