Rivers have always been indispensable to the establishment of human settlement
in any area. One of the main benefits of a river is that it provides water to vast
areas around it, which is the basic element for plant and animal life. Water from the rivers is harnessed by man for agriculture (growing crops) and to perform daily activities such as cooking and bathing. As a river flows, it carries with it particles of clay and other mineralised soils, which deposit in the area around the river, making it rich and fertile. Also, rivers contain several plants, animals and aquatic life which are used by man for food and commercial benefits.
A major advantage of rivers is that of navigation (transportation) via them. Men have used rivers to travel from one land to another since ancient times. Discoveries of new places happened as men invented various types of boats and ships, suited to
the nature of the river they were crossing, and travelled far from their native lands
along the rivers' paths. Majority of North and South America and Africa have
been discovered this way. Today rivers serve as important trade routes and
transport channels between cities and countries. Ports and harbours dot the banks
of big and small rivers where carriers transport items like livestock and lumber.
Rivers provide energy in the form of hydroelectricity. A large amount of energy is
trapped in the rivers, created by the motion of the water as they flow from higher to lower points. This energy is abundant in fast moving mountain rivers and waterfalls. It is harnessed by turbines and energy-plants, producing electricity, which accounts for about 25% of all energy generation in the world. The biggest advantages of this energy are that it is non-polluting and created from a renewable source. On a smaller scale, river water is used to turn water-wheels which produce sufficient energy to sustain smaller communities such as riverside villages.
|A lake is a body of water enclosed on all sides by land. Lakes usually have fresh |
water, though some lakes like the Caspian Sea and Aral Sea have salty water. The
term "lake" comes from the Greek word "lakkos" meaning a "hole" or a "pond".
Lakes are formed mainly by the action of glaciers on the land around them. When glaciers move, they cut deep valleys into the surrounding land. At the same time, the glacial deposits (rocks, gravel, soil) act as dams around the edges. When the glacier melts, the resulting water collects in within the 'dams', forming lakes.
Some lakes form in limestone regions when rainwater, which is slightly acidic, eats
through the rock. This forms tunnels and passages. These holes cause the tops of
the passages to collapse, causing depressions known as sinkholes. The edges of some of these sinkholes get lined with clay, which does not allow the rainwater to flow away. This forms a lake.
Lakes are formed in a number of other ways as well. Sometimes when a volcano explodes, it blows away the top of the mountain, leaving a crater behind. Once the lava (molten rock) cools, it forms a basin that seals the crater's surface. Rainwater collects in this basin and forms a lake. Movements of the Earth's crust known as
| faulting cause the ground to split into two. This causes a gap in between which a lake may form. Rain or groundwater fill craters left by meteorites to form lakes. Oxbow lakes are born when a river changes its course, leaving behind some part of it collected in a basin. Lakes made artificially by building dams are called reservoirs. |
|An oxbow lake formed by a river changing its course >|
| Lakes usually have no outlets or inlets. They are fed by underground streams or|
springs. Sometimes rivers run into lakes and feed them. Rain is the third source of
water for lakes. When there are long periods of drought, lakes dry up and leave
behind soil that is rich in minerals and salts and hence very fertile.
Lakes have thriving ecosystems of their own, with numerous plants, insects and
animal species living in and around the waters. Water-plants exist on the banks and
in the waters of the lake. Common dwellers include bugs, snails, fish, frogs and a
variety of birds like flamingoes, storks, cranes and kingfishers. Land animals also
frequent lakes as a source of food and water.
|Lakes are important to the environment. Large lakes help keep the temperature of the places around it at moderate levels. This is because the waters remain cooler |
than air in summer, and warmer than air in winter. Water, moisture and fertile soil from the lakes help irrigation and crop-growing in the neighbouring areas. Dams are built on rivers to form artificial lakes which are then used for irrigation or for generating hydroelectric power (energy from falling water).
Larger lakes also provide a means of travel between places and connect cities forming trade routes. Ships, barges, freighters and boats are used to navigate lakes. Lakes also serve as sources of fish and other important flora and fauna, used as food and for various industries. Last but not the least, lakes provide recreation to people who can boat, swim, fish, and even ice-skate when lakes freeze over!
rnFollowing are some of the greatest freshwater and saltwater lakes in the world :
Lake Baikal, or Baykal, is the deepest lake in the world, with its deepest point at 1,620 metres below the sea level. It is located in Siberia in Russia. It is also one of
the oldest lakes in the world, formed about 25 million years ago by faulting of the Earth's crust. Baikal has the largest volume of fresh water of all the lakes. It is fed by 336 rivers, while only one river, the Angara comes out of it. Baikal and its surrounding area is now a protected national park.
The lake has numerous plants and animals despite the
|^ A NASA satellite picture|
showing the great fault
that contains Lake Baikal.
|extreme cold of the Siberian winters. Several species|
|are found only in and around the lake, such as a fish named golomyanka. The surface of the lake is frozen from January to May. The Baikal area produces timber, cellulose, fish and paper. Hydroelectricity is generated by a dam on River Angara. |
|Lake Tanganyika of Africa is the longest fresh water lake in the world, and the second deepest. It is located in east-central Africa. It is bordered by Burundi and |
Tanzania on the East, and Congo and Zambia on the West. Tanganyika is fed by the River Rusizi. River Lukuga drains out of it. Dr. Livingstone, the 'lost explorer', was found by Henry Stanley on the banks of Lake Tanganyika in 1871, when Henry asked the now-famous question, "Dr. Livingstone, I presume?"
|^ A NASA satellite photo |
of Lake Tanganyika.
Lake Titicaca is the highest navigable lake in the world. It is situated in the Andes range on the border of Peru and Bolivia in South America. It is located at 3,812 metres above sea level. The Desaguadero River flows out of Lake Titicaca and empties into Lake Poopo in Bolivia.
Titicaca is the seat of many ancient Indian towns, whose ruins are found on the islands present in the lake. Several Indian villages exist on the river banks. Lake Titicaca is a good location for fishing, especially trout.
|^ An ancient Indian gate stands|
over a pathway leading to the
calm expanse of Lake Titicaca.
|Lake Victoria in east-central Africa is the world's second-largest fresh water lake. It |
is the largest lake in Africa and is traversed by the equator. It is the biggest source of water for the world's longest river, the Nile. Lake Victoria lies partly in the three countries of Tanzania, Kenya and Uganda. It is named after Queen Victoria of Britain.
|The Great Lakes are a group of five lakes situated on the U.S.-Canada border. They form the world's largest group of fresh water lakes. They are the most important|
inland waterway in North America. The five lakes are Lake Michigan (the only lake entirely in the United States), Lake Erie, Lake Huron, Lake Ontario and the largest, Lake Superior. The last four lakes are shared by the U.S. and Canada. The Great Lakes were formed about 250,000 years ago by the melting of a glacier.
|^ A NASA satellite photo|
shows the Great Lakes.
Lake Superior is the world's largest fresh water lake. The Lakes remain covered by ice in winter, and during summer experience some violent storms.
The Lakes have contributed greatly to the development of industry and water-travel in North America. They are connected by three sets of canals, the Welland Canals, the Soo Canals and the St. Lawrence Seaway. The Great Lakes drain into the St. Lawrence and Chicago rivers. A large number of large ports lie on the banks of the Lakes, from which ships travel to all parts of the world.
|^ A busy port on lake Michigan|
The Caspian Sea is the world's largest lake. It is called a sea as it has salt water, but as it has land on all sides, geographers also call it a lake. The Caspian Sea is located
between Asia and Europe in the Caucasus Mountains. It lies below sea level. The most important rivers running into it are the Volga, Ural, Emba, Terek and Kura.
The Caspian Sea has deposits of petroleum and natural gas, and abundant fish of both freshwater and saltwater species. But it is becoming smaller because the rivers that carry water to it bring in less water than it loses due to evaporation and extensive irrigation.
|The Caspian Sea >|
|One of the most beautiful lakes in the world is Lake Geneva. It is situated in central |
Europe between Switzerland and France. It was formed by a natural damming of
River Rhone. It is surrounded by the Jura Mountains in the north and the French
Alps to the south. The Lake has a crescent (curved Moon) shape. Major cities on the lake are Geneva, Lausanne, Vevey and Montreux, all in Switzerland. Lake Geneva is one of the biggest tourist attractions of Europe.
|Part II of Rivers And Lakes focuses on the most prominent rivers on the Earth.|
|An imaginary line called a |
watershed or a drainage
divide separates the drainage
basins of major rivers.
|Lake Victoria is known as Victoria Nyanza in the African language, Bantu. |
| Indians residing around |
Lake Titicaca in the Andes
navigate the Lake using
canoes made of reeds
and named totoras.
|^ A secluded shore of Lake Huron in North America.|