A river forms from water moving from a higher elevation to a lower elevation, 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 people have built a dam to hinder a river's flow, the lake that forms is a reservoir. The river serves many purposes, from drinking water to wildlife habitat to a recreation spot for the whole city. The phrase "river of life" is not just a random set of words. Rivers have been essential not only to humans, but to all life on earth, ever since life began. Plants and animals grow and congregate around rivers simply because water is so essential to all life.
It might seem that rivers happen to run through many cities in the world, but it is not that the rivers go through the city, but rather that the city was built and grew up around the river. For humans, rivers are diverted for flood control, irrigation , power generation , public and municipal uses, and even waste disposal.
Are rivers one of your favorite places? If so or if not, why not vote for your favorite water body in our Activity Center! Large rivers don't start off large at all, but are the result of much smaller tributaries, creeks, and streams combining, just as tiny capillaries in your body merge to form larger blood-carrying arteries and veins.
The mighty river featured in this image is called the Yarlung Tsangpo as it courses through the Tibetan Autonomous Region of China. Credit : NASA. The most simplistic answer is that all the water in a river comes from the sky—and that is certainly true, as streamflow is one part of the water cycle. It is also true that most of the water flowing in rivers comes from precipitation runoff from the surrounding landscape watershed.
But, the water in a river doesn't all come from surface runoff. Rain falling on the land also seeps into the Earth to form groundwater. 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. Groundwater seepage can sometimes be seen when water-bearing layers emerge on the land surface , or even on a driveway!
Look at the diagram below. The ground below the water table the blue area , is saturated, whereas the ground above the gray area is not. 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, 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.
Water from melted snow is fresh and that is why most rivers possess fresh water. On the other hand, a creek is a small river or a rivulet. Creeks have all the characteristics that rivers possess with a few differences between the two. A slender channel flanked by islands may also be called a creek. A creek does not usually drift out into a new channel or form a new branch or even have tributaries. A river, on the other hand, is more likely to branch out into different or multiple routes.
In addition, it is also more likely to have tributaries that connect. Since a creek can flow under the surface of the earth, it possible for the sea to be the origin of a rivulet.
A river is more likely to have its origins from a place with a high altitude which equates to rivers mostly having fresh water. From their definitions, it is possible to discern that a river is larger and deeper compared to the miniature creek. This is why most rivers have freshwater content. Many ancient civilizations, towns, and cities built near rivers flourished due to the fact that they can serve many purposes; soil on the banks of river is fertile, rich, and highly suitable for farming.
Rivers provided trade routes and were good sources of food. Today, hydroelectric energy can often be harnessed from running river currents, which can also sometimes be used to transport logs and other heavy materials downstream. There are times when a river connects to another river, and it can also branch out to tributaries such as brooks and creeks. A creek is usually smaller and shallower than a river.
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