Lakes are static bodies of water surrounded by land on all sides and are always located on the land surface. The size of lakes may vary as some lakes are as small as ponds having a meager aerial extent of a few square meters while some lakes are as large as the Great Lakes. It comprises Superior, Michigan, Huron, Ontario and Erie Lakes of North America. These are also called the Great Lakes. The water in the lakes is supplied from different sources. Either it is replenished by rainfall or precipitation or from the underground water table. There are different types of lakes which are classified based on their origin.
Types of Lakes
Glacial Lakes
Glacial lakes are produced by various erosional and depositional actions of the glaciers. The erosive actions of valley glaciers usually create features such as cirques, U-shaped valleys and the irregular surface of glaciated lowlands and provide depressions for the development of lakes.
Examples of the glacial lakes are Reindeer Lake in Canada, Lake de Loux of Switzerland, Lake di Coma, Lake Lago Maggiore and Lake Lago di Garda in Italy, the Great Lakes of North America and Ladoga and Onega Lakes of USSR.
River Lakes
These lakes are created by both depositional and erosional activities of the rivers. These lakes are called ‘Oxbow lakes’. When a river meanders in its plain course, the flow undercuts the outside banks of the bends and silts are deposited on the inside narrowing the channel. With the passage of time, a breakthrough cut off the meander due to which an ox-bow lake is formed by the “Cut off of a loop”. Oxbow lakes generally do not exist for longer because they are cut off from the source of water i.e. the main river. Examples of such Oxbow lakes can be found in the middle and lower Ganga plains and in the Brahmaputra Valley.
Wind-Made Lakes
The Aeolian lakes are formed due to the erosive and depositional action of winds. Salt marshes, Oases, Playas and Salinas are examples of such lakes. These lakes are formed either due to the filling of the inter-montane valley depressions by flood water or due to tapping the water tables by wind deflation. The Qattara Depression westward from Cairo in Egypt is 125 m below sea level. Other examples of such oases in Egypt are Baharia, Farafra, Dakhla and Khargo. These are located above sea level.
Volcanic Lakes
Volcanic lakes are formed at the top of the volcanic mountains when the volcanoes become dormant and the materials within the volcanoes get solidified. This leads to the formation of the Caldera which gets filled up with water to form Caldera Lake. For Example, Crater Lake, of Oregon, USA occupies a Caldera which is about 10 km in diameter. It is formed by the collapse of a lofty composite cone volcano.
Chemical Action Based Lakes
The solvent action of rainwater on limestone regions usually produces hollows which form small lakes. Such lakes are formed when the solution in hollows becomes clogged by residual clays leading to the formation of the lakes after the accumulation of water in them. Karst Lakes are the fine examples of chemical action-based lakes. These lakes can also be produced by the collapse of the limestone roof which may produce long narrow lakes which were once underground. The Lac de Chaillexon in the Jura Mountains near the boundary between France and Switzerland is an example of such a lake.
Tectonic Lakes
Hollows in the earth’s crust formed due to large-scale warping or fracturing can lead to the formation of lakes. Such lakes as formed due to the tectonic movements of the earth are termed as tectonic lakes. Examples of such lakes include the Caspian Sea in the USSR, Victoria Lake in East Africa, Lough Neagh in North Ireland and Titicaca Lake in Peru/Bolivia. Such lakes are also formed by the back tilting of valley systems. Lake Kyoga in Uganda is classified into this type.
Rift Valley Lake: Rift Valley Lake is also an example of a tectonic lake. Rift valleys are the usual sites for lakes in their steep-sided linear depressions. The Jordan-East Africa rift valley is a striking example of such a type. The Dead Sea, Lake Tanganyika, Lake Nyasa (Malawi), etc., are also examples of rift valley-type lakes. These lakes appear elongated thus illustrating the elongated character of a rift valley.
Differential Faulting: Differential faulting can also lead to the development of lakes in the Great Basin in the western United States. The basin comprises Lake Baikal in the USSR. It was formed by faults. Lake Baikal (1,620 meters) is the deepest lake in the world.
Meteorite Lakes
The impact of giant meteorites can cause large scars on the earth’s crust. These are called Astroblems (star wounds). The crater formed by the meteorite impact is almost circular in striking contrast with the irregular outlines of the ice-eroded depressions occupied by the other lakes. These craters are filled with water and become lakes. Lonar Lake in Maharashtra, India is a fine example of such a lake. The largest known crater lake is the Ashanti Crater (Lake Bosumtwi) in Ghana. It has a diameter of over 9.5 km.
Man-Made Lakes
There are many man made lakes which have been made by man for various purposes such as electricity production, irrigation etc. Govind Ballav Pant Sagar, Govind Sagar Lake etc. are fine examples of man-made lakes in India. Mead Lake above the Hoover (Boulder) Dam on the Colorado River USA, Powell Lake above the Glen Canyon Dam on the Colorado River USA, Kariba Lake above the Kariba Gorge Dam on the Zambezi River, on the border between Zambia and Zimbabwe and Govind Ballav Pant Sagar above the Rihand Dam on the Rihand river are examples of manmade lakes..
Abandoned-Mine Lakes
The abandoned open cast mines sometimes are filled with water to form lakes. The Norfolk Broads mines in the Netherlands were flooded and abandoned by the peat cutters. As these depressions could not be drained in the course of time they became lakes. Similar lakes have been formed in the abandoned diamond mines in Kimberley, South Africa.
Oceanic Lakes
The lakes which are formed by the depositional and erosional activities of the sea waves are usually termed oceanic lakes. The lagoon is a fine example of an oceanic lake. The waves which approach towards the shore and pass into shallow water, topple over or break. The line of such breaker waves may be several hundred meters from the shoreline.
These waves wash forward loose bottom materials and drop them just landward of the line of breakers forming a submarine ridge almost parallel to the coast. These ridges grow in height and appear first above sea level as a series of narrow islands. The process of deposition by waves fills up the gaps and connects them to form off-shore bars. Between the off-shore bars and the mainland, there is a shallow body of water which is known as lagoons.
Formation of oceanic lakes due to sand dunes: Sands which are largely composed of minute fragments of marine shells migrate from the seafloor to the beach where the prevailing winds are on shore. This drifting sand is blown landwards and piled up to dunes. Such sand dunes can be found along the Kerala coast where they are locally called Teris. These dunes have led to the formation of a large number of shallow lagoons and backwaters which are called Kayals in Kerala.
Importance of Lakes
There are a large number of ecosystem services which are provided by these lakes. They are:
Reservoirs of Water: Lakes are reservoirs of water and provide a number of services such as availability of water for drinking, factories, irrigation and generating hydel-power.
Equitable Climate: Lakes provide the maritime climate to its nearby surroundings by making summers cool and winters mild. Hence, the annual range of temperature around lakes is narrow.
Flood Control: Rivers which pass through the lakes in their course seldom cause disastrous floods. For Example, the Wular Lake and the Dal Lake do not allow the Jhelum River to be flooded. However, the rivers such as the Brahmaputra are subjected to very great floods every year due to the lack of such lakes.
Fisheries: The inland fisheries are an important source of fish across the world. Lakes are hence important sources of inland fish production. Currently, 70% of India’s fish is produced by the inland fisheries.
Source of Common Salt: Many inland lakes which are usually located in arid and semi-arid regions are great sources of common salt. Sambhar Lake, Didwana Lake, Pachpadra Lake and Kuchman Lake are major lakes from where the salts are obtained.
Transport: Lakes can be used for navigation. The Great Lakes-St. Lawrence Waterway of the USA and Canada is a fine example.
Tourists’ Hotspots: Lakes are also revered as iconic tourist hotspots. The Valley of Kashmir is a fine example of such a lake where tourists throng in large numbers due to the large number of lakes.
Note for UPSC Aspirants: For UPSC aspirants interested in exploring further, here are some keywords to guide your research:Glacial lakes, River lakes, Wind-made lakes, Volcanic lakes, Chemical action-based lakes, Tectonic lakes, Rift Valley lakes, Differential faulting, Meteorite lakes, Man-made lakes, Abandoned-mine lakes, Oceanic lakes, Reservoirs of water, Equitable climate, Flood control
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