Rivers

A river is a stream of water that flows over land. It is vital for people, plants and animals. Rivers offer routes for the transportation of people and goods. A river’s water shapes landscapes and produces electricity.

Parts of a River

Rivers usually begin high up in the mountains as a tiny flow of water that comes from rainfall or melting ice. Sometimes rivers originate in a lake or a layer of groundwater that comes up to the surface as a spring.
Rivers consist of three sections.

Upper Course

The upper course is the beginning of a river. It is also referred to as a stream. In this section, it is very small and transports very little water, which flows quickly down a steep hillside. As it moves downward, a stream gets bigger. Other streams, called tributaries, flow into it.
When streams carry more and more water they grow into rivers. They cut their way through landscapes and change the face of the earth. Erosion is caused by the flowing water that cuts into bedrock and makes a river’s bed deeper. Waterfalls, canyons and other landforms are typical of the upper course of rivers. Rivers transport rocks of different sizes and deposit them as they move along.

Middle Course

During the middle course, a river gets flatter. Water moves at a slower pace. This section of a river cannot transport very big rocks anymore; instead, soil, gravel, sand and silt sink to the bottom of the river. More and more material is deposited as sediments.

Lower Course

The lower course is the broadest part of a river. Huge masses of water flow slowly across flat plains. Such rivers do not transport any rocks with them; they deposit fine material and silt. As they wind their way towards the sea rivers start curving back and forth gently, creating meanders.

At its mouth, a river flows into the sea. Estuaries form in places where there are ocean tides. Rivers open themselves in triangular form to the vast ocean. Freshwater mixes with the salt water of the ocean. Deltas form in places where river water deposits sand and silt and gradually moves the coastline further into the sea. Many kilometers from the coast, rivers split up into several smaller rivers.
Many elements have influenced the form of rivers and valleys. Throughout the Ice Age, glaciers widened river valleys and shaped them as a U. In deserts, rivers dry up during certain months of the year when there is no rainfall. In karst regions, water trickles through cracks into the ground and rivers often flow under the surface.

River basins

A river basin consists of a main river and the tributaries that flow into it. Big river systems can have hundreds of tributaries and drain huge areas of land. The largest river basins are in the tropical rainforest. The Amazon River basin covers an area of almost 7 million square kilometers, about 40% of the South American continent. The Congo basin drains much of central Africa.

Every landmass on earth belongs to a watershed, the area that catches all the rain and leads it into rivers.

Rivers in history

Rivers have always played a dominant role in history. Many civilizations have been built along great rivers. Ancient Egypt developed along the Nile, Mesopotamia spread along the Euphrates and Tigris region. The Indus valley is among the oldest civilizations in history.

Rivers gave humans farmland to grow crops as well as a route to travel and trade their goods with other people. As time went on some rivers were turned into important waterways and used to transport goods to the inner parts of a continent. The St. Lawrence Seaway, for example, finished in 1959, connects the St. Lawrence River with the Great Lakes of North America, making it possible for cargo ships to travel as far as Chicago. A series of locks and canals helps rivers overcome differences in sea level.

Small towns have grown into big cities because they are situated on rivers: Paris on the Seine, London on the Themes, St. Louis on the Mississippi are only a few examples.

Humans have learned to use the power that moving water creates. Dams along rivers generate a large part of the electricity used in some countries. Engineers have regulated many rivers in order to stop flooding and prevent a river’s bed from cutting too deep into the soil.

Pollution of rivers

Human development has caused a lot of damage to rivers and their natural environment. Since the Industrial Revolution, factories have been dumping industrial waste into rivers. Especially paper and chemical plants need a lot of water for cleaning processes.

As cities grew larger and larger sewage systems had to be created to treat dirty water from the population. Nuclear power plants are often situated next to rivers because they need large amounts of cooling water. Pesticides and chemicals released through fertilizers can cause diseases and kill fish and other animals.

The 10 longest rivers of the world

Nile (Africa) - 6,600 km
Amazon (South America) – 6400 km
Yangtze (Asia) – 6,300 km
Mississippi-Missouri (North America ) 6,200 km
Yenisei-Angara (Asia) 5,500 km
Yellow River (Asia) 5,400 km
Ob-Irtysh (Asia) 5400 km
Paranà(South America) 4880 km
Congo (Africa) 4,700 km
Amur (Asia) 4,400 km

Words

amount = quantity
basin = flat area from which all the water around it flows into the same river
bed = the flat ground at the bottom of a river
bedrock = solid rock in the ground, below the soil
broad = wide
canyon = deep valley with very steep sides of rock; a river usually runs through it
cargo ship = ship that does not carry people but goods that we need
coastline = where sea and land meet
connect = link
consist of = made up of
crack = small line in an object
create = make
crops = plants, like wheat or rice, which farmers grow and sell as food
deposit = put, leave
desert = very dry area with little or no rainfall
develop = grow
development = growth
disease = illness
dominant = very important
downward = here: towards the sea
drain = to collect all the water of a region
dump = put, throw
electricity = power that is carried by cables and wires; it is used to give us light and heat and to make machines work
element = part, factor
engineer = person who plans and makes roads, bridges etc..
environment = the world around us
erosion = action by which landscapes or rocks are slowly destroyed by rain, wind or the sea
especially = above all
estuary = place where a river gets wider and wider and mixes with the sea
face = surface, top
fertilizer = substance that is put on the soil to make crops grow better
flow = to move steadily over an area
freshwater = water from rivers and lakes
further = more
generate = produce
gently = slowly , softly
glacier = large mass of ice that moves slowly down a valley
goods = products
gradually = slowly
gravel = small stones
groundwater = water that is below the earth’s surface , in rock formations
huge = very big
humans = people
influence = change
instead = in something’s place
karst = area which is made up of rocks that let water through them
landform = landscape
lock = part of a canal or river that is closed off by gates, so that the water level can be raised or lowered to move ships up or down
meander = to bend a lot and make curves
melt = when ice turns into water
mouth = where a river flows into the sea
nuclear power plant = building which makes electricity by splitting atoms
offer = give
originate = come from , start
overcome = here: to go past
pace = speed
pesticide = chemical used to kill insects and small animals that destroy farm crops
plains = large area of flat land
plant = factory
population = all the people who live in a place
prevent = stop
process = action, job
refer to = call, name
regulate = control, here: to make rivers flow smoothly
release = set free
sea level = the normal height of the sea; it is used for measuring how high other places are
section = part
sediment= material that slowly sets down to the bottom of a river
series = network, chain
several = many
sewage system = place where dirty water from people and factories is made clean again
shape = form
silt = sand, mud and soil that a river carries and deposits
situated = located
soil = the top layer of the earth, on which plants grow
split up = separate
spread = extend, become larger
spring = place where water comes up naturally from the ground
steep = not flat
stream = very small river
surface = the top layer of an object
throughout = in all of
tide = the natural rise and fall of the sea
tiny = very small
trade = buy and sell products
triangular = shape with three sides
tributary = stream or small river that flows into a larger one
trickle = drip
valley = area of low land between two mountains, usually with a river flowing through it
vast = very large
vital = very important
waste = unneeded material
watershed = high land that separates two river systems
waterway = river or canal that boats can travel on
wind = make curves

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