(The Gist of Kurukshetra) FLOODS AND DROUGHTS IN INDIA:


On an average, every year India gets 4,000 billion cubic meters of water
mostly through rainfall and some snowfall. However, this is the average, over a
large number of years. In any given year, the rainfall, and hence the river
flow, may vary from this average, on the lower side, or on the higher side. Such
rainfall instances, very low or very high, are called hydrologic extremes.
Floods and droughts, both are a result of hydrologic extremes. This short
article explains the phenomenon of floods, and droughts, why these occur, and
to manage them.


The term ‘floor’ is commonly used to describe any inundation by water. But
here are two distinct mechanisms that can cause inundation. A rainfall takes
place somewhere in the upstream catchment, and consequent high flow in the river
may spill out in to the habitation are some where downstream. This is called
flood. In India, 33.5 m.Ha (million Hectares)
of area is floor prone, and out of this, on an average, some or 7.5 m.Ha is
affected by floods every year. The floods are most common in Ganga and
Brahmaputra river basins.

Causes of Floods

• A very heavy rainfall in the upstream catchment causes a very large river
flow. The width of the river through the city downstream is not adequate to
carry that flow, and the water spills over, beyond the usual river banks.
• Nature lake Burst: A landslide takes place in the river and acts like a
dam.Water accumulates behind it, creating a lake.
• Breach of Embankments: Embankments are constructed along both banks of the
river to protect human habitation. If the embankment breaches, the river flow
enters the habitation.
• Dam Break: This is very rare, but a man made dam many burst releasing a large
quantity of water and causing a flood.

 Managing Floods

 Floods can’t be entirely prevented. The approach to flood management is
a combination of protection from floods of less severity, reducing the damage by
flood forecasting and disaster relief in case of floods of larger severity.
Flood management options are typically divided in two types, structural – i.e.
comprising some construction of embankments, and flood control reservoirs; and
non-structural,,comprising flood forecasting, flood plain zoning, and disaster

Embankments are low bunds constructed along the river bank, to “contain” the
river flow and prevent it from spilling in to the areas of human activity.

Finally, if a flood does occur, relief operations are needed to rescue
marooned people and provide them with shelter, food and water, and medical help.

Draining Congestion

Inundation in cities is usually due to the inability to drain out the rain
water fast enough. Construction of buildings impends the flow of water over the
land; solid waste may choke the storm water drains, which are in any case not
adequate, and in coastal cities, the problem is compounded if a heavy rainfall
coincides with high tide. Mumbai was inundated on 29th August 2017. And at the
same time, the city of Houston in USA was also inundated, for worse than Mumbai,
due to the same mechanisms. It may sound harsh, but short duration inundation
due to drainage congestion, is a problem the cities many have to live with.


Like floods, droughts are also a hydrologic extreme. But drought neither have
a clearly defined beginning, nor a clearly defined end. At times, it may not be
even possible to say with certainty that a droughts has set in. drought I a
phenomenon that extends over a long duration. Droughts are divided in three

Meteorological drought is when the rainfall is deficient.
Hydrological drought is when there is inadequate water in the rivers
and or aquifers.
Agriculture drought is when there is inadequate water supply to crops
start wilting.

About 153 mha area of the country is drought prone. Till about 1900, drought
meant famine and widespread deaths. As many as 11 famines were recorded between
1769 and 1901 with an estimated 20 million deaths. However, not it is possible
to transport large quantities of food grains to drought affected area, and to
some extent also transport water, and the famine deaths are avoided.
Nevertheless, drought brings serve distress to rural people even in this age.

Inter Basin Water Transfer (IBWT)

The geographical area from which the rainfall accumulates and drains out
through a river, is called its river basin. By an ingenious design of canals,
and at times by pumping, it is possible to take water from a surplus basin to a
deficit basin. Such water transfer is called inter basin transfer of water. The
earliest plan to construct canals to link certain rivers, was in the year 1858
by Sir Arthus Cotton, a British engineer. However, the purpose of his plan was
inland water transport, and not water distribution. Around the same time,
as a means of transport became feasible, and his plan of interconnecting the
rivers was set aside.

• Irrigation to an additional area of 35 mHa;
• Generate 34,000 MW of hydro power;
• Provide drinking water to a large number of villages and towns;
• Drought mitigation in Andhra Pradesh, Karnataka, Tamil Nadu,M.P., W.B., Bihar,
U.P., Haryana, Rajasthan, Jharkhand and Gujarat.
• Flood control in Ganga, Brahmaputra, Mahanadi and Godavari basins;
• Facilitate inland navigation;
• Development of fisheries;
• Infrastructure development;
• Employment generation
• Improve aquatic environment by improving EFR, during lean season.

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