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In the Janakpuri the first sand formation exists upto a
depth of 28m below ground level (bgl), which is followed by layer
of Kankar and silt which exists upto a depth of 36m bgl, which is
followed by impermeable layer of clay and kankar from 36 to 40m bgl.
This clay layer is followed by layer of Kankar and silt upto 50m depth
A
comparative study of water level map of 1960 and 2002 shows in Janakpuri
the water level which was at 2 to 5m below ground level has gone down
to 10 to 20 mts bgl.
In
Janakpuri the occurrence of fresh water in alluvium formation is limited
to shallow depth. The groundwater from tubewells are saline to brakish
in nature.
IV.CASE
STUDIES
1.MIRA
MODEL SCHOOL |
RAINWATER AVAILABLE FOR HARVESTING
Total rooftop and surface area: 16,200 Square metres (Sq.m). Average
annual rainfall in Delhi : 611 millimetres (mm). Total volume of rainwater
harvested : 4,454 cubic metres (m³), or 44,54,000 litres. This
is 45 per cent of the total water harvesting potential.
WATER SUPPLY SOURCE
The non-potable water requirement is mainly fulfilled by the two borewells
in the campus. The municipal water supply takes care of the drinking
water requirements.
RAINWATER HARVESTING SYSTEM
Rooftop rainwater and surface runoff harvesting
WESTERN SIDE OF THE BUILDING
A part of the rooftop along with the surface runoff from the paved
area near the playground is intercepted in a drain that is connected
to a desilting chamber. The silt-free water from the chamber (measuring
300mm x 300mm
x 300mm) enters a recharge structure of 1m x 1m x 1m. To facilitate
recharge, a 15m deep borewell of 100mm diameter is provided inside
the recharge well. A layer of pebbles and sand filled inside the recharge
well acts as filtering media, ensuring the quality of runoff that
is being recharged.
EASTERN SIDE OF THE BUILDING
Rooftop rainwater and surface runoff in the eastern side of the building
is channelised through a stormwater drain to a recharge structure
measuring 2m x 2m x 3m. To facilitate recharge, an 8m deep borewell
of 100mm diameter is provided inside the recharge well.
THE FOOTBALL GROUND
Runoff from the playground is captured on the northwestern corner
of the playground in a recharge well of 1.5m x 1.5m x 1.5m by means
of a trench filled with pebbles surrounding the pit. The 14m deep
borewell provided inside the recharge well facilitates recharging
of the aquifer. Overflow from this structure drains into another recharge
well of dimensions 2m x 2m x 2m through a network of pipes linked
through chambers.
The project was implemented in June 2001. The cost of the entire rainwater
harvesting system was Rs 1.20 lakhs.
RAINWATER AVAILABLE FOR HARVESTING
Total area (Ward 1 and Ward 13): 4125 square meters (Sq m)
Average annual rainfall in Delhi: 611 millimeters (mm)
Total volume of water harvested: 1280 cubic meter (m³) or 12,80,000
litres
This represents 50.78 per cent of total rainwater harvesting potential.
WATER SUPPLY SOURCE
Water supply in these wards is fulfilled by two borewells located
inside the jail premises.
RAINWATER HARVESTING SYSTEM
Rooftop rainwater and runoff from unpaved areas:
Ward 1
In Ward 1, the rooftop rainwater from the barracks and the surface
runoff from the unpaved area are collected in a low-lying area between
the buildings. This water is collected by a collection chamber measuring
0.5m x 0.5m x 0.5m, which is covered by a perforated RCC slab. The
water collected in the chamber is diverted to recharge well measuring
1m x 1m x 2m with a recharge bore of 150mm diameter and 10m deep.
The recharge well is filled with layers of pebbles and coarse sand,
which act as filtering media to improve the quality of the water harvested.
Ward 13
The rooftop rainwater from the buildings and the surface runoff from
the open areas are collected in a low-lying area located at southwest
corner of the ward. This water is collected in a collection chamber
measuring 0.5m x 0.5m x 0.5m, which is covered by a perforated RCC
slab. The water collected in the chamber is diverted to a recharge
well measuring 1m x 1m x 2m in size with a recharge bore of 150mm
diameter and 10m deep. The recharge well is filled with layers of
pebbles and coarse sand, which act as filtering media to improve the
quality of the water harvested.
The implementation was completed in November 2002 and the water level
on February 2003 was recorded at 9.40m bgl.
The cost of the entire rainwater harvesting system was Rs 0.2 lakh.
| V.RECOMMENDATION FOR AUGMENTATION
OF GROUNDWATER |
The intake capacity of recharge structures will be low
in shallow water table condition. Hence in Janakpuri where the ground
water level is below 8m rainwater harvesting can be taken up.
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