Method
A - Utilisation of dried up wells
Lowering
of groundwater levels in the last 2 to 3 years, led to
the drying up of many of the open and some shallow tubewells.
Instead of discarding, these dried up wells can be utilised
as recharge wells by connecting them to the water outlet
pipes from the roof tops. This cost effective process
not only saves the precious rainwater going as waste,
but also helps in restoring the local ground water availability.
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Method
B - Decentralised percolation through water spreading
and longitudinal trenches.
In this
method, applicable to houses having larger open areas,
the run off water from the roof top can be diverted into
the bare soil or garden in the premises of the households.
The top soil may be loosened before monsoon, for better
recharge. Apart from this, a longitudinal trench of 1.0
to 1.5 m. depth with a width of 0.5 to 1.0 m., may be
dug and filled with well rounded pebbles, gravel and sand
in order to store excess run off water during rainy days
that will eventually percolate.
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Method
C - Centralised percolation through pits.
Pits are
dug deeper and away from the building foundations, where
the soil is more pervious. The pits may be back filled
with permeable material like pebbles, gravel and sand
for better percolation. The top sand layer need to be
cleaned and relaid once in two years to remove the settled
silts for restoring the percolation. Commonly, pits with
1.0 m. dia. and 2 to 3 m. depth are recommended. The combination
of water spreading and pit recharge is better for more
groundwater recharge.
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Method
D - Recharge through shafts
Groundwater
recharge through shafts is recommended for steep slope
areas. The shafts are deep pits with a width of one meter,
length of two meters and depth of 10 to 15 m. preferable
terminating above the aquifer (water bed) level. The shafts
may be cased or uncased on the top, but are back filled
with permeable soil, which facilitates more effective
and faster percolation and mitigation of biological and
chemical pollutions.
Typical
filter units and Recharge Well/Shaft
Recharge
through Tube Well in hand rock area
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Direct
recharge of the aquifer through open wells will be an
easier and less expensive process in the shallow aquifer
region. The roof top run off water can be directed into
the open wells through pipes and settling pit, to avoid
possible turbidity. The tubewells used for groundwater
drawal can also be used for recharge with a valve control
between the storage tank/settling pits and tubewell. In
addition to the run off from roof top, part of the run
off from paved and other open area, can also be diverted
to the recharge pits/trenches.
The rain
water, from the roof tops, can be used directly for washing
purposes and for storing the water temporarily in settling
sumps for later use. This method is less expensive but
more effective. Industries, multistoried buildings and
Government Organisations can implement it, as they depend
mostly upon groundwater sources for all purposes. Depending
upon the size and configuration of the plot area, the
dimensions and location of the trenches and pits are to
be planned. In general, trenches are recommended with
a minimum width of 0.5 m. to a depth of 1.5 m. all along
the compound wall with a number of pits of 2 to 3 m. depth
and 1Êm. dia. The combination of trenches and pit
recharge is better for more groundwater recharge.
Method
E - Recharge through wells
Recharging
through wells involves direct discharge of rain water
through a settling sump to the underground water bed.
These wells can be used both as production wells and recharge
wells. The advantages of direct injection of roof top
run off water are:
- harvesting more roof top rain water
- relatively high rate of recharge
- utilisation of ground water during non rainy days
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Method
F
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