Water
is the most precious natural element. Not surprisingly, it is also the most
used and therefore, the fastest depleting resource.
While
water is being used in several ways, urban cities mostly depend on groundwater
consumption, owing to its wide availability and easy accessibility. From
small-scale users like domestic households, to larger industries and
agricultural farms, groundwater is needed on a daily basis. This has led to its
indiscriminating extraction and use, facing the human population with a major
crisis, which, if not dealt with in time, can result in catastrophic
consequences.
The
high rates of usage and limited natural recharge have led to the severe
depletion of the water table, resulting in acute dearth of drinking water in
several parts of the country. The problem escalates during summer, when the
yield of several groundwater wells and tube wells often comes down to zero.
Today, more than seventy-two percent of the country falls under the ‘crucial
zone’ due to groundwater over-exploitation.
Groundwater levels in India. Red indicates depletion and
blue indicates recharge
What’s the solution?
One
compelling solution to combat groundwater depletion is artificial recharge, a
method of manually augmenting the amount of groundwater. This method has been
prevalent in India for some 30-40 years and has been successful in various
parts of the country.
The
first phase of artificial recharge was before 1960, during the Green Revolution,
when groundwater was still abundant. The second phase was between 1960 and
1990, and the third phase is from 1990 till date, when groundwater depletion
rate has risen to an alarming rate (Todd, 1980).
However,
artificial recharge is not a new phenomenon. This method of conserving water
has been in use since the ancient times and even now, tanks and ponds are found
all over peninsular India that are used for drinking, washing, bathing and
irrigation.
Methods of Artificial Recharge
Artificial
recharge of groundwater can be done in either direct or indirect ways or a
combination of both.
Direct Methods
Flooding: In this method, water is spread
as a sheet on flat topography. This water then vertically infiltrates to
replenish the amount of groundwater. This works well when the aquifer is
shallow.
Basins: Another method for shallow aquifers, this involves filling basins with
water. This water percolates into the soil and adds to the level of
groundwater. The amount of water entering the aquifer depends on the
infiltration rate, the percolation rate and the capacity for horizontal water
movement. (Todd, 1980)
Source: www.nicra-icar.in
Natural wastewater treatment can
also be used to recharge groundwater by allowing treated waste water to
percolate into the soil.
Source: www.nicra-icar.in
Ditches and Furrows: In
areas with irregular topography, ditches and furrows provide maximum water
percolation. This technique requires less soil penetration and is less
sensitive to silting. (0’Hare, at al 1986)
Recharge Wells: This
works like a tube well and is used to pump in treated surface water. These
wells can also be used as pumping wells during summer. This is a costlier
method of artificial recharge as it requires a special kind of tube well
construction. (Image below: bore well recharge. Source: sswm.info)
Indirect Methods
The
indirect groundwater recharge is done by setting up pumping stations near
hydraulically connected water bodies, like lakes and streams. The amount of
surface water depends on natural factors like the amount of rainfall and its
frequency. (0’Hare, et al1986)
Modular rain water harvesting can
also be classified as a form of indirect recharge as this water is stored in an
underground water storage tank and
then diverted to existing wells. Water conservation can also be done by
creating rooftop gardens that not
only combat pollution and increase rainfall but also help in storm water management, resulting in
less erosion and floods.
Source:
sswm.info
Success Stories
Andhra
Pradesh: The Andhra Pradesh Farmer Managed Groundwater System has taken
voluntary steps to reduce groundwater pumping, successfully.
Gujarat:
Several water conservation and recharge projects have been highly successful in
Gujarat, like the Sardar Patel Water Recharging Programme, that built check
dams in association with the villagers, and Gujarat Green Revolution Company,
that propagated sprinkler and drip irrigation technology.
Check dam
Chennai:
Rainwater harvesting was made mandatory by an ordinance in July 2003 and all
buildings were required to have rainwater harvesting structure.
The Last Word
It is
not too late to save Nature and prevent groundwater depletion. We cannot stop
the use of water but we can take measures to stop indiscriminate and
unsustainable exploitation of groundwater. Artificial recharge is a movement in
India, promulgated by the government, NGOs, community leaders, farmers and
local people. The challenge now is to carry it into the future with the help of
research and development programmes that will resolve the water depletion
problem to a great extent.
References:
Central Ground Water Board (1994), Manual on Artificial Recharge of Groundwater, Government of India
Todd, D.K. (1980), Groundwater Hydrology, Wiley, New York
O’Hare, M.P., Fairchild, D.M., 1986, Artificial Recharge of Groundwater
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