DO YOU KNOW ? : RAIN WATER HARVESTING
What is rainwater harvesting?
Rainwater harvesting is the
storing and collection of rain water that runs off from tops of roofs, open
spaces like parks and roads or especially prepared ground. This water can be
used variously for purposes like drinking (after treatment), household use,
livestock or even irrigation. It is also used for recharging groundwater,
that is replenishing the water that has been extracted from the aquifers.
Why should rainwater be
Much of the water that we
receive as rain simply runs off and gets wasted. In a country like ours
where there is so much of pressure on water resources due to growing
population pressures, it makes immense sense for us to store up this water
and put it to good use. This water can be a useful supplement to the water
available from other sources, thereby augmenting the total water
availability. In fact, in some regions, rain is the only source of water
available, and that too, in highly erratic spurts. In such regions
harvesting of rainwater is the best option available to people, and has been
known to bring about marked betterment in their living conditions, for
example in many parts of Gujarat and Rajasthan.
Rainwater harvesting is also
very important for recharge of groundwater as there has been massive over
extraction of ground water in many parts of the country. Rainwater
harvesting not only replenishes the store of underground water, it also
improves its quality by effecting dilution of pollutants and other harmful
Besides these, rainwater
harvesting also prevents local flooding in many areas, caused by the run off
How can rainwater be harvested?
A major point in favor of
rainwater harvesting is that the structure for this can be made from
inexpensive, locally available material. It works both in individual
households and for small communities. Rainwater harvesting structures can be
made anywhere - individual homes, apartments, offices, institutions, slums,
cities, villages - and ~y anyone - individuals or small communities.
Rainwater harvesting structures
can be simple or complex. The main components in a rainwater harvesting
system consist of a catchment area from where water is collected -
this could be either from the ground like parks, playgrounds, roads,
pavements, agricultural field etc, or from the rooftops - the channel or
conduit through which water passes from the catchment structure into the
storage area - these could be drains, pipes, rectangular or semi circular
gutters or channels made of PVC material, galvanized iron sheets or even
bamboo trunks cut vertically into two and the storage tank or other
structures where the water gets collected. The size of tanks would
depend on the amount of water available and the amount needed for use. The
tanks can be made from RCC, plastic, galvanized iron etc. Even dried bore
wells, tube wells etc can be used for collecting water. If rainwater is
being harvested for recharge purposes, there need to be appropriate
structures for this, for example subsurface dykes built into an aquifer,
recharge of abandoned wells, service tube wells, recharge pits etc. Besides
these the rainwater harvesting structures also requires arrangements to
maintain the quality of water. Thus there have to be arrangements to ensure
that the first flush of rainwater which would contain contaminants, is
allowed to flow out. Filters made of cloth, charcoal, sand etc are put in
place to filter out pollutants.
Is rainwater harvesting a new
concept in India?
No, Indians have been
harvesting rainwater since ancient times. Some of the traditional systems
include Tankas which were small underground tanks built in houses in
Rajasthan, especially Bikaner; Khadim or Dhora, which are embankments
built along low hills lopes lying under rocky uplands for collecting water
that runs down the slopes and using it for agricultural purposes later on;
Bao/is or stepwells of Gujarat and Rajasthan, TheAhar Pynes of
South Bihar- Ahars are catchment basins embanked from three sides and
pynes are channels leading off from the third side; canals of West
Bengal; Tanks, Phads and Bhandaras of of Maharashtra, Keres or
tanks of Kama taka or Zings of Ladakh which were tanks for collecting melted
glacier .Most of these traditional structures are now defunct, but efforts
have been initiated by many communities to revive these.
What rainwater harvesting
technique is most popular in urban areas?
The technique for collecting
rainwater from rooftops is most popular in urban areas. Many state
governments have passed laws making rainwater harvesting mandatory for all
new buildings/ apartment etc. Some are even giving incentives in the form of
rebate on property taxes.
How is rainwater harvesting
being done in rural areas?
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