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In the Aurbindo Ashram area the first Layer of clay and
kankar extends to depth of 14m bgl. This is followed by layer of kankar
and silt from 14 to 25m below ground level. This is again underlain
by layer of clay and kankar which extends even beyond 40m bgl.
A comparative
study of water level map of 1960 and 2002 shows in Aurbindo Ashram
the water level which was at 5 to 10m below ground level has gone
down to 20 to 30 mts below ground water level.
In
Aurbindo Ashram fresh water occurs at all depths.
IV.CASE STUDIES
SRI AURBINDO MARG |
RAINWATER AVAILABLE FOR HARVESTING
Total area: 95, 870 square metres (Sq m)
Average annual rainfall in Delhi: 611 millimetre (mm)
Total volume of water harvested: 16, 366 cubic metre (m³) or
1,63,65,879 litres
This represents 43 per cent of the total rainwater harvesting potential.
WATER SUPPLY SOURCE
The water requirement is met through three tubewells and is supplemented
by Municipal water supply.
RAINWATER HARVESTING SYSTEM
In this campus the rainwater from various catchments, including rooftop,
surface runoff from open areas, is harvested. Rooftop rainwater harvesting:
a) Mirambika school
The rooftop rainwater from the northern part of this building is diverted
to a dry open well of 18m depth and 2m depth through a network of
pipes and collection chambers. The silt from the rooftop rainwater
is filtered by using a desilting chamber of 0.6 m x 0.6m x 2.5m depth.
b) Mother's International school
The rooftop rainwater from the northern part of this building is drained
to the playground located on the northern part of the building. This
roof water, in addition to the surface runoff is harvested by two
recharge wells of 1m x 1m x 2m in dimension with a recharge bore of
16m depth. The rooftop rainwater from the southern part of the building
is canalised using a network of interconnecting pipes and collection
chambers to a recharge well near the existing borewell. The recharge
well is 1.5m x 2m x 2.5m in size with a recharge bore of 150mm diametre
and 16m depth. A layer of pebble and sand is used to ensure proper
filtration.
c) Tapsya building
The rooftop rainwater from this building is collected through a network
of pipes and chambers and diverted to the dry open well of 15 m depth
and 2m in dia. The rooftop rainwater passes through a desilting chamber
before it is diverted to the recharge well.
d) Office block
Rooftop rainwater from the office block is diverted to an abandoned
borewell, which was converted to a recharge well by making a pit of
1m x 1m x 2m around it. The recharge well is filled up with pebbles
and which acts as filtering media. Filtered water enters the borewell
and recharges the subsurface aquifers.
Surface water harvesting:
a) Near Mirambika School
Part of the rooftop rainwater from the Mirambika School and the surface
runoff from the unpaved areas are collected in two collection chambers
which are provided with perforated slabs. This surface runoff is diverted
to a recharge well 1.5 m x 2 m x 2.5m in size with a recharge bore
of 150 mm in diametre and of 16m depth. The recharge well is filled
with filtering materials to ensure good water quality used for recharge.
b) Playground area
The surface runoff from the playground area is collected in collection
chamber constructed at the northwest corner of the playground. This
collection chamber was converted to a recharge well by drilling a
recharge bore of 150 mm diametre of 18 m depth. The recharge wells
are filled with a layer of pebble and sand for filtering the surface
runoff, which also improve the quality of water harvested.
c) Power station area
Surface runoff on the eastern side of the Mother's International school
building is collected in a open drain and diverted to a recharge well
adjacent to the power station near the existing borewell. The recharge
well is of 2.5m x 3m x 3m in size with a recharge bore of 20 m depth.
d) Near Ashram building
Rooftop rainwater, along with the runoff from the paved areas surrounding
the Ashram building are collected in a recharge well of 2.5m x 1.5m
x 2m in size with a recharge bore of 20m depth. The recharge well
is filled with a layer of pebble and sand for filtering the surface
runoff that improves the quality of water harvested. The implementation
was completed in January 2003 and the water level as on February 2003
was recorded at 27.4m below ground level (bgl).The cost of the entire
rainwater harvesting system was Rs 4.0 lakh.
| V.RECOMMENDATION FOR AUGMENTATION
OF GROUNDWATER |
In
this area the rainwater can be diverted to a depth of 15 to 20mts.
By doing this the rainwater will under go a natural filtration in
the subsoil before it reaches the main aquifer. The recharge bore
in the recharge well should be of 15 to 20mts bgl.
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