Rivers are large natural bodies of water that flows from a source high above to a either a sea, lake or an ocean at a lower level. The water is usually fresh water, that is without salt. Small rivers are often called creeks, brooks or other terms. Rivers can be a good source of fish for food.
Rivers have influenced where people site places to live. They use them to transport goods from place to place. London was built by the Romans because of its location, that is not too wide that a bridge could not be built across it. The River Ganges is highly revered in the Hindu Religion and has been personified by the goddess Ganga. Hindu's flock to bathe in the river even though it has been highly polluted by industry on the banks of the river. As most river are fresh and contain limited or not at all salt, they are used by many people as a source of water. Water is removed from the river, cleared of impurities and then pumped into houses for use. It is said that water could be used at least four times before it finishes the end of its journey. Water would be pulled from the river, purified, used, returned to the river and then pulled again for use.
In olden days and to a lesser extent nowadays, water provides energy for a mill through a wheel which as it turns, produces the momentum needed for the task (e.g. flour, textile production). Nowadays, rivers are dammed so that they can be used to provide electricity for the local population. When a dam is built, land on the side closest to the source is flooded and water is let through to generate turbines. As land has to be flooded, damming is highly controversial and can result in loss of land used by animals and humans alike. The largest dams in the world including the number one, The Three Gorges Dam are in China. The Hoover Dam in America has been designed to work without minimal if any human interaction. If humans were to disappear in a blink of an eye, the dam would continue producing electricity long after other electricity producers have ceased.
River start up high then flow down to the end which can either be a Delta or a Mouth. A river can have multiple sources which later merge into one. The River Nile is a good example of this. It has two main contributory rivers called the Blue and the White Nile. The source is usually where the rain water collects or where ice has melted. Along the way, smaller rivers known as tributaries can run into the main river. The tributary River Lea starts from Luton and discharges into the River Thames. Along the way, the river can drop many feet which is known as a waterfall. As mentioned above, the river can be used as a means of electricity through dams or water turbines placed on the river. Rivers can change their route and eventually break off part as it curves so much causing an ox-bow lake. This can take place over tens or hundreds of years. The river will either end at a mouth or a delta which is where the river splits into smaller rivers before ending in a lake, sea or ocean.
The largest waterfall is the Angel Falls in Venezuela, 3212ft high. It is not named because of religious angels but named in honour of American pilot James Crawford Angel who landed on top of the mountain where the water runs off. He spent 11 days climbing down leading his party including his wife to safety. The next largest is the Victoria Falls, named after Queen Victoria of Britain by Scottish explorer Dr. David (I presume) Livingstone. Its volume is much greater than that of the Angel Falls. It is located on the borders of Northern Zimbabwe and Southern Zambia. Some waterfalls can cause the corrosion of the rock and force the creation of a canyon as what the River Colorado has done with the Grand Canyon. The canyon took over six million years to create.
When rivers become too full, water will spill over onto the land. Flooding can happen after a period of ice thawing at the end of winter or when it has rained for a long period of time. The ground can only soak up so much of the water so it overspills onto the land. Properties that are built on flood plains are worst hit.