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Meeting
Water Demands
in Water Stressed Regions
AVM S Sahni
ssahni@devalt.org
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Rainwater
harvesting, its conservation and sustainable utilization can remedy the
water shortages in most, if not all, drought prone areas of our country
quickly and cheaply with the active participation of the people. There
are three main sources of water viz. rain, surface water and ground
water, rain being the prime source of all water. India receives about
400 million-hectare meter (m. Ha. m) of rain and snow every year.
Another 20 M.Ha. M. of flow is added from the neighbouring countries.
Out of 420 M.Ha.M., the river flows account for approximately 180 M.Ha.M.,
ground water another 67 M.Ha.M. and remaining 173 M.Ha.M. merely
moistens the top soil or evaporates immediately from the soil. Out of
180 M.Ha.M. of river flows nearly 150 M.Ha.M. enters the sea and the
neighbouring countries thus hardly 30 M.Ha.M. of river water are
utilised. Capturing part of the flood waters of major rivers can
substantially increase the water availability. In addition, even if
20-25 M.Ha.M.of the 173 M.Ha.M., which merely moistens the top soil or
evaporates, can be captured through rainwater harvesting. We can
further augment the water availability and minimise the tremendous
pressure on the country’s ground water and river water resources.
Our ancestors,
realising the limitation of the number of soft water days/hours viz
hardly 100 hrs of rainfall per year and nothing in the remaining 8660
hrs. had devised various methods to harvest rainwater and its storage
such as :
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Roof top harvesting and storing in tanks built in
the courtyard/compound.
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From community and private lands, rainwater was
collected and stored in artificial wells.
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Part of monsoon run -off from overflowing streams
and rivers was tapped.
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Small / Medium check dams were built on streams.
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Water tanks were a normal feature in most
villages and lakes in some.
All this changed
in the last 100-150 years when we witnessed two major shifts in water
management in India. The first was that the State took over the role of
water management from individuals/communities. The second was that
simple technologies/practices of managing rainwater, in vogue since
long, was discontinued and over-exploitation of river and ground waters
through large dams-cum- canal network and tube wells became the norm in
its place. As ground and river waters constitute a small portion of the
total rainwater in our country over-exploitation is putting a severe
strain on it with its attendant ill effects.
Over 90% of the
rural population depends upon ground water for their drinking water
needs and over 50% of the cultivable land is irrigated by open/tube
wells. The rapid decline of water table due to excessive withdrawals is
posing a serious threat to our country's hard-earned food security and
the shortage of drinking water during the summer months is becoming
endemic.
Rapidly increasing
population, unplanned economic development and urbanisation is further
adding to the problem of water shortage. We have, thus, to augment the
surface and ground water on a war footing if we want to avert water
famines. Contamination of ground water brought about by human
activities is another area which has to be tackled as the highest
priority. Ground water charging will go a long way to mitigate the ill
effects of contamination as by the ingress of fresh water in the aquifer
the contamination levels of ground water get reduced.
Water harvesting
implies the utilization of rainwater to augment the surface and ground
water. The surface water is increased by constructing tanks, check dams
and impounding reservoirs. These, in turn, also raise the ground water
level as surface water seeps in the aquifer by the action of gravity.
In addition, an
integrated watershed development programme that implies the use of
mechanical and vegetative measures of soil/moisture conservation such as
bunding/gully plugging, percolation tanks, etc. and afforestation /
pasture development will greatly increase the quantum of ground water.
Similarly, roof-top water harvesting can provide water for household
use, especially in urban areas.
Despite the huge
investments made by the nation in drinking water schemes during the past
50 years and not withstanding the claims of most states, adequate
potable drinking water is still not available in nearly two lakh
villages of the country. Rainwater harvesting in most of these villages
can easily solve the drinking water problem. A village with an annual
rainfall of, say, 400 mm. can capture four million litres of water on a
plot of one hectare which at 30 litres per day per individual. This
would cater to the needs of nearly 360 people for the whole year.
Ground water is
the cheapest and most practical means of providing water for irrigation
and household needs in rural areas where nearly 70% of our population
live. Ground water is superior to surface water because the soil
provides a filtering medium, is generally free from pathogenic agents
and requires no/little treatment. Also, its supply is available on call
and even in dry seasons. Ground water reservoirs do not suffer seepage
losses like surface water and even evaporation losses are negligible.
Ground water reservoirs can be developed quickly, cheaply and near the
place of use whereas surface water storage/reservoirs require suitable
sites which are not easily available. In addition, they entail huge
costs and displacement of people, and a long gestation period. It has
been our experience that in most check dams, cost of developing assured
irrigation potential works out to Rs. 10,000/- to Rs. 15,000/- per
hectare whilst in the case of large dams and canal network, it would be
well over one lakh rupees per hectare. With the beneficiaries providing
“Shramdaan”, the cost of check dams can be reduced
substantially. A check dam can recover its cost of construction
through an increased agricultural production in one or at best two
seasons.
Case studies by
CSE in Gujarat, Rajasthan and MP have clearly revealed that three years
of continuous drought (1998-2000) in most part of these states which
adversely effected millions of humans and animals had little or no
adverse effect on those villages which had adopted rainwater harvesting
measures and its judicious use. Our experience in the last 10-12 years
also confirms that farmers in the vicinity of check dams constructed by
our organisation had enough water in their wells to take two to three
crops and meet the drinking water needs of humans and animals in the
three hot months of April, May and June.
Water holds the
key to ecological regeneration, which will ultimately lead to poverty
alleviation.
We can drought-proof the
nation during the next 15-20 years if we succeed in making it a
people's movement which will enhance local food security, provide
sustainable livelihoods by the millions and create a confidence in our
people especially, amongst the youths, that nothing is yet lost and
India can truly become a
self-sufficient, prosperous and strong nation in the next two to three
decades.
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