lake classification of lakes · lake – classification of lakes lakes are among the most varied...
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Lake – Classification of Lakes
Lakes are among the most varied features of the earth’s surface. A lake is a large body of natural water accumulated in a depression. Lake basins are formed due to endogenous geological processes like tectonism and volcanism and exogenous activities like landslides, glaciation, solution, river and wind action.
Lake and Its Classification
They vary tremendously in size, shape, depth and mode of formation. The tiny
ones are no bigger than ponds or pools, but the large ones are so extensive that
they merit the name of seas, e.g. the Caspian Sea. The Caspian Sea is the largest
lake regarding the area. The deepest lake in the Lake Baikal in Siberia.
Lakes occupy about 1.8 % of the earth’s surface. About 280 000 cu.km of water
exists on earth in the form of lakes. This is 0.19% of the total volume of water in
the hydrosphere.
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Advantages of lakes
The major role played by lakes and reservoirs is the regulation of stream flow.
Lakes provide water for drinking, factory, irrigation and generating hydel-
power.
Lakes are a good refuge for an enormous variety of flora and fauna.
The lives of the people, in a region, are greatly influenced by the presence of a
lake in that area.
In some places, lakes are good sources for water supply for drinking.
Lakes help in the growth of the fishing industry.
The salt lakes yield common salt. For example, Sambar lake
Lakes are helpful in controlling the weather and moderating local climate- Lakes
cool the air in summer and warm it during winter. They also enhance the
humidity.
Lakes have an aesthetic appeal and are helpful in recreation; tourists are
attracted due to lakes which have boating, swimming and a good landscape
around.
Lakes are used for navigation. For example the Great Lakes in North America
Lakes also help in flood control as rivers passing through the lakes in their
course seldom cause disastrous floods. The Wular lake and the Dal lake do not
allow the Jhelum river to be flooded and due to lack of such lakes, the
Brahmaputra is subjected to very great floods every year.
Lakes only a temporary feature?
Lakes are thought to be only a temporary feature of the earth’s crust. Eventually,
they will be eliminated by the dual process of draining and sitting up. In regions of
unreliable rainfall, lakes dry up completely during the dry season. In the hot
deserts, lakes disappear altogether by the combined processes of evaporation,
percolation and outflow. Though the process of lake elimination may not be
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completed within our span of life, it takes place relatively quickly regarding
geological time.
Classification of lakes
When there are a large number and variety of lakes, people tend to classify them.
There are several types, kinds and categories of lakes in the world. Classification
helps us to understand and visualize the relationships and helps us to
communicate. The most common classification of lakes is based on the size or
dimension of lakes, whether it is small, big or very large.
Lakes are mainly classified on the basis of:
a) Nature of Inflow-outflow
b) Origin
c) Trophic levels
a) Classification based on inflow-outflow
Temporary and Permanent Lakes
1. Temporary Lakes -These lakes may exist temporarily by filling up small
depressions of undulating grounds after a heavy shower. In such lakes rate of
evaporation is much greater than the rate of recharge through precipitation.
They are usually saline. They are subject to extreme fluctuations in water level.
Example – Badhkal Lake, Faridabad
2. Permanent lakes – Permanent lakes carry more water than could ever be
evaporated. These are very deep. They have some perennial source of inflow of
water such as a glacier. They are usually freshwater lakes. Example – Dal Lake
Freshwater and Salt lakes
1. Freshwater lakes – Most of the lakes in the world are freshwater lakes. They
are usually found in low lying areas and are fed from streams, rivers and runoff
from the surrounding area. e.g. Great Lakes of North America, Lake Baikal in
Russia, Lake Wular and Loktak Lake in India.
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2. Salt Lakes – Salt Lake is an inland body of water situated in an arid or semiarid
region, having no outlet to the sea, and containing a high concentration of
dissolved salt. These lakes exist in regions of low precipitation and intense
evaporation. Because of intense evaporation, the concentration of salts
increases in the water body, turning them saline. Playas or salt lakes are a
common feature of deserts. Example – Great Salt Lake of Utah, USA, Dead Sea
etc.
Great Lakes of North America
b) Classification based on origin or mode of formation
The following are the various ways in which lakes can be formed. Each of them is
placed in a different category, though in a few cases the lake could have been
formed by more than one single factor
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1) Lakes formed by earth movement
Tectonic Lakes
These lakes are formed by filling up with water in the tectonic depressions
created due to warping, sagging, bending and fracturing of the earth’s crust.
Such depressions give rise to lakes of immense sizes and depths.
Example – Lake Titicaca, Chile, the Caspian Sea etc.
Rift Valley Lakes
These lakes include some of the oldest, deepest and largest lakes around the
globe.
Due to faulting, a rift valley is formed by the sinking of the land between two
parallel faults, deep, narrow and elongated in character.
Water is collected in these troughs
Often their floors are below sea level.
The best example of this is the East African Rift Valley which includes such lakes
as Lake Tanganyika and the Dead Sea etc.
2) Lakes formed by Volcanism
Crater and Caldera Lakes
A natural hollow called a crater is formed by blowing off of the top of the cone
during a volcanic explosion.
Crater may be widened and enlarged by further subsidence into a caldera.
These depressions are normally dry.
In dormant or extinct volcanoes, due to rainfall straight into these depressions
which have no superficial outlet, a crater or caldera lake is formed.
Examples – Lonar crater lake in Maharashtra, India, Crater Lake in Oregon, USA
and Lake Toba in Sumatra etc.
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Lava-blocked Lakes
In volcanic regions, it is common to find a stream of lava that flows across a
valley
This stream of lava may occasionally become solidified and block the valley thus
forming a lake basin
This basin may get filled up due damming up of the river due to solidified lava
Example – The Sea of Galilee which is an inland lake was created due to blocking
of the Jordan valley by lava flow
One more type of lake formed due to subsidence of a volcanic land surface is
included under this type. Under this type of lake, the crust of a hollow lava flow
may collapse. The subsidence leaves behind a wide and shallow depression in
which the lake may form. E.g. Myvatn Lake of Iceland
3) Lakes formed by Glaciation
Cirque or tarn lakes
Cirque, a common landform in glaciated mountains, is often found at the heads
of glacial valleys.
A glacier on its way down the valley leaves behind circular hollows.
These circular hollows, in the heads of the valley up in the mountain, are called
cirques.
Cirques are very deep, long and wide troughs or basins.
The head and sides of these cirques have very steep to vertically dropping high
concave walls
Often, a lake of water can be seen within the cirques after the disappearance of
the glacier. Such lakes are referred to as the Cirque or tarn lakes
They are also called as Ribbon lakes
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Example – Red tarn in the English Lake District and Chandra Taal (Himachal
Pradesh) in India
Cirque or Tarn Lakes
Kettle Lakes
These are depressions in the outwash plain left by melting of a large mass of
stagnant ice
They are irregular in shape, and also these lakes are not very large or deep
Example – Kettle-lakes of Orkney in Scotland
Rock-Hollow Lakes
These lakes are formed by ice scouring when valley glaciers or ice sheets scoop
out hollows or depressions on the surface
Such lakes are abundant in Finland
Two more types of a glacial lake are formed due to “damming up of valleys by
morainic debris deposited by valley glaciers” and “deposition of glacial drifts in
glaciated lowlands”.
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4) Lakes formed by Erosion
Karst Lakes
Karst lakes are formed in depressions, carved out by solvent action of rainwater
on water-soluble rocks such as limestone, gypsum and dolomite.
The collapse of limestone roofs of underground caves may result in the
exposure of long, narrow lakes that were once underground.
The shallow bed of these lakes is usually an insoluble layer of sediment so that
water is impounded, resulting in the formation of lakes.
Many karst lakes only exist periodically but return regularly after heavy rainfall.
Example – the Lac de Chaillexon in the Jura mountains
Otjikoto Karst Lake in Namibia
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Wind deflated lakes
These lakes are formed in arid regions and deserts
The depressions are created in deserts due to deflating action of winds
Groundwater may seep out in these depressions forming lakes
Excessive evaporation causes these to become salt lakes and Playas
Example – Great Basin of Utah, USA
5) Lakes formed by deposition
Ox-bow lakes
In large flood and delta plains, rivers rarely flow in straight courses. Loop-like
channel patterns called meanders develop over flood and delta plains
During a flood, a river may shorten its course by cutting across its meandering
loops, leaving behind a horse-shoe shaped channel as an ox-bow lake
Example – Ox-bow lakes are a common phenomenon in the floodplains of
Lower Mississippi, USA and Rio Grande (Mexico), Kanwar Lake Bird Sanctuary in
Bihar, India is one of Asia’s largest oxbow lakes.
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Meandering or river and Formation of Oxbow Lakes
Barrier Lakes
These lakes are formed by landslides, avalanches and such other processes
These processes cause damming up of the river by blocking the valleys
These lakes are short lived as the large piles of loose fragments soon give way
under the pressure of water. The sudden release of water from these lakes like
this can also cause floods
Example – Lake Gormire in Yorkshire, blocked by a landslide
6) Man-made lakes
Artificial lakes
Besides natural lakes, man has now created artificial lakes
Artificial lakes are created by erecting a concrete dam across a river valley
These dams help in creating a reservoir by impounding river water
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Guru Gobind Sagar Lake which supports the Bhakra Nangal Hydel Project is an
example of an artificial lake in India
c) Classification based on trophic level
Eutrophic Lake
Eutrophic lakes have very high levels of biological productivity.
The excessive level of nutrients, especially phosphorus and nitrogen gives rise
to an abundance of aquatic plants in these water bodies.
Usually, the water body will be dominated either by aquatic plants or algae.
Eutrophication might occur naturally or due to human impact on the
environment.
Some of Highly Eutrophicated Lake in India include Udaisagar Lake (Rajasthan)
and Dal Lake (Kashmir)
A Eutrophic Lake
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Mesotrophic Lake
Lakes with an intermediate level of productivity are called mesotrophic lakes.
The nutrients level of these lakes in medium or moderate.
They usually have clear water with submerged aquatic plants
Oligotrophic Lake
An oligotrophic lake is a lake with low primary productivity, as a result of low
nutrient content.
Algal production in these lakes is relatively low.
Often, they have very clear waters, with high drinking water quality
Paleolakes
A paleolake is a lake that existed in the past when hydrological conditions were
different.
Often, Paleolakes are identified based on relict lacustrine landforms such as
coastal landforms that form recognizable relict shorelines, referred to as paleo-
shorelines.
Paleolakes can also be recognized by characteristic sedimentary deposits that
accumulated in them and any fossils that these sediments might contain.
Evidence of prehistoric hydrological changes during the time of their existence
can be found from the sedimentary deposits of paleo-shorelines and paleo-
lakes.
Types of Paleolakes
Former Lake – A former lake is a lake which is no longer in existence. Former lakes
include prehistoric lakes and permanently dried up lakes resulting
from evaporation or human intervention. A good example of a former lake is
Owens Lake in California, USA.
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Shrunken Lake – A shrunken lake is a lake which has drastically decreased in size
over geological time. A good example of a shrunken lake is Agassiz Lake, once
covering much of central North America.
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