Childrens Illustrated Encyclopedia

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TribuTaries

The streams and rivers

that flow into a big river

are called its tributaries.

rapids

Fast, swirling currents form

where water flows down a steep

slope. These parts of the river are

called rapids.

Floods

rivers can overflow with heavy

rain, or when water surges up

from the sea. Flooding is severe

in low-lying places, such as parts

of brazil in south america,

which are often hit by tropical

storms. destruction of

surrounding forests may be

increasing the flow of water,

making floods worse.

uses oF rivers

Great rivers that flow across whole countries carry boats

that take goods from place to place. some rivers have dams

that build up huge stores of water in reservoirs. This water is

used to supply towns and cities, irrigate crops, and generate

electricity in hydroelectric power stations. rivers are also a

source of fish, but many rivers are now

polluted by farms and factories.

WaTer runs doWn from high ground, cutting out a channel in

the rock as it moves. This flowing water forms a river, which can be

fed by a melting glacier, an overflowing lake, or a mountain spring.

rivers shape the landscape as they flow: the water sweeps away soil

and eventually creates deep valleys in the land. one of the world’s

deepest valleys, cut by the Kali Gandak river through the Himalayas,

is 3.4 miles (5.5 km) deep. rivers also flow deep underground, slowly

wearing away limestone rocks to form caves.

rivers are important for transportation and as a source of

water, which is why most big cities lie on rivers. The longest

rivers are the nile river in africa, which is 4,145 miles

(6,670 km) long, and the amazon river in south

america, which is 4,007 miles (6,448 km) long.

river sysTem

small rivers and streams feed a large river with

water. a river system consists of the whole

group of rivers and streams. a watershed,

or high ridge, separates one river

system from another. streams

flow in opposite directions

on either side of a watershed.

delTa

The river sometimes

fans out into separate

streams as it reaches

the sea. The streams

dump mud, which

forms an area of

flat land called

a delta.

WaTerFall

The river plunges over a shelf

of hard rock to form a waterfall.

GorGe

The waterfall

slowly wears away the

rock, cutting a deep gorge.

river valley

The river carries along stones and mud,

which grind against the riverbed and

sides, deepening and widening

the v-shaped valley.

Flood plain

Farther down the river, the

valley flattens out. This area,

called the flood plain, is

sometimes submerged during

floods. The river runs through the

plain in loops called meanders.

niaGara Falls

The niagara river plunges almost

180 ft (55 m) at niagara Falls,

which is situated on the border of

the united states and Canada.

rHine river

The rhine river is an important

trade route. barges carry goods

between towns in northern europe.

Rivers

oxboW laKe

The river cuts

through the neck

of a loop by

wearing away the

bank. material is

deposited at the ends

of the loop, eventually

forming a lake.

Some rivers do not form

deltas but flow into the

sea through a single

wide channel called

an estuary.

Weathering on the valley sides

breaks up soft rock and soil. This

material falls into the river and

is carried away by the current.

Rain feeds the

river system.

Find out more

dams

Glaciers and ice caps

lake and river wildlife

lakes

rain and snow

Water

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