Competitive Exams: Lakes

Lakes are static bodies of water, usually but not necessarily fresh water on the land's surface which is surrounded by lands on all sides.

Lakes are not permanent features on the earth's surface. Lakes are formed, developed and ultimately obliterated due to silteration and upliftment of lake beds due to diastrophic movements. For example, several lakes have disappeared in the Kumaon region like SukhaTal and SarraiyaTal around Nainital. The highest lake of the world Tso Sekuru (Tibetan plateau) is located at the height of 18284 ft and the lowest is the Dead sea-1300 ft below the sea level.

Charateristics of a Lake

  • Are variable and changes with time

  • Height has nothing to do with

  • Some lake have greater depths-e. g Baikal lake of Siberia is more than 1.6 km deep (1600); some are shallow and almost become dry during the summers and hence are called seasonal lakes. Size does not matter. It can be as big as the Caspian Sea and csn also be as small as Tarn Glacier lake (very small).

Preconditions of a Lake

Basins, depressions and troughs are the most ideal places for the development of lakes. Troughs:

  1. A system of low atmospheric pressure; characterized by much greater length and width.

  2. A valley that has been overdeepened by glacial erosion.

  3. The lowest part of the wave formed between two crests. There should be proper and regular supply of water. The water table should be high.

Classification of Lakes

  1. On the basis of salinity:

    1. Fresh Water Lakes: Very low amount of salt flow of water; Eg. Kumaon (U. P). Dal and Wular lake of Kashmir.

    2. Saline Lakes: Are also called salt lakes and are relatively common. These are found mainly in semi-arid and arid regions of warm climate where the rate of evaporation is very high. These are of four types

      1. Alkaline lakes: Having the dominance of salts of Sodium and Potassium Carbonate:

      2. Bitter lakes: Contains salts ofSpdium Sulphate

      3. Borax lakes: Have high proportion of Borax

      4. Mixed lakes: Have a mix-ture of different salts. Examples of saline/salt lakes: Sambhar and Panch-bhadra lakes (Rajasthan), salt lakes of Lingtzi Tang (Kashmir), Chilka lake (Orissa), are all in India. Examples of saline/salt lakes (outside India) Great Salt lake (Utah-USA) -a remnant of Bonneville lake, a fresh water lake.

Lake Classification

  1. Curstal lakes, Waker and Honey lakes in USA, Lahontan, Caspian Sea, Aral Sea, Dead Sea.

  2. Diastrophic lakes: Lakes. Examples, Crater lakes of Oregon in USA, Tana lake (Ethiopia), Nicaragua (Central America).

  3. Lakes formed due to mass translocation of Rock Waste-This includes land slides etc. Examples: San CristoBal, Slumgullion Mudflow (Colorado, USA). In 1968, a landslide took place in Darjeeling and two lakes were formed due to damming of Tantakhola-a tributary of Jaldhaka river.

  4. Glacial lakes: These are also called moraine lakes. Examples: Grand lake of Colorado (USA), Naini/Nainital lake (UP). Lakes of Canada, Norway, Sweden and Finland.

  5. FluviaI lakes: These are formed due to rivers. They are of two types:

  6. Oxbow lakes: e. g. Wjilar lake in Kashmir.

  7. Delta lakes: Godavari Delta, Ganga Delta called beels. Ponchastrian lake of Mississippi, Mayeh lake of Nile Delta, Marigot lake of Niger Delta.