Bangalore Parks are more ‘GREENER’
Paradise found!
Now the lush green
parks are self sufficient when it comes to meeting their water requirements in
Bangalore… read on….
Bruhat
Bangalore Mahanagara Palike has on area of around 825 sq.km. in the city
limits. The civic amenity open area includes bus-stops, play grounds,
educational institutions, recreation parks etc. There are around 1060 parks in
Bangalore. The total land cover dedicated for 1060 park is 770 hectares. Total
water requirement of these parks at the rate of 2 litre per sq.m. for around
253 non-rainy days is 3896 Million Liters.
The
rainwater harvesting proposed for parks in Bangalore is mainly planned to
harvest water from the open area including the paved walk paths and the
structures inside the park. It is planned to allow the rainwater to percolate
mainly in the green areas which are not paved and cemented. During heavy rains,
the excess flow from the saturated soil of the green area will flow into the
walk path which is paved. The rainwater which is flowing in this paved area is
guided to go out to the nearest storm water drain (following the natural
gradient).
The
rainwater harvesting interventions will intercept the outlet of the rainwater
channel which is carrying the storm water from the park (at the exit point of
the park). A silt trap is designed to collect the debris and the silt flowing
along with the rainwater. The relatively clean water flowing out of the silt
trap is systematically diverted into the infiltration gallery. The accelerated
infiltration galleries are the structures which are open wells created using
pre-cast cement rings.
The
accelerated recharge wells are the dug wells inside the park at the lowest
level (gradient). These wells are typically 1.5m, 2m and 3m in diameter with
depth of around 3 to 6m. Pre-cast cement rings which are of appropriate
diameter and height of around 0.3 to 0.5m. These rings are placed one above the
other without any cement mortar in between joints. Loose aggregates (stones)
are packed in the annular place between the cement rings and the excavated
well. The entire well inside the cement rings is kept empty without any filler
material. These cement ring wells will have a safety metal grill at the ground
level. The last cement ring of the well is placed over the safety grill to
prevent easy access into the well. These accelerated infiltration galleries –
cement ring wells are closed at the top with a cement slab. The silt traps
which are harvesting surface flow of rainwater from the parks will discharge
rainwater through a pipe into these wells. Most of the water percolates into
the soil and joins the ground water underneath.
A
shallow bore well / tube well is drilled closer to these accelerated
infiltration galleries to collect the harvested water underground. These bore
wells will supply water for the plants in the parks during the non-rainy days.
Some
of the parks which have larger paved areas, playgrounds or structures are
provided with underground sumps to harvest rainwater directly. The harvested
rainwater is used for the toilet blocks and also for watering the plants.
Details
|
Data
|
Units
|
Total area of parks in Bangalore (770 hectares)
|
77,00,000
|
Sqm
|
Number of Parks
|
1,060
|
No
|
Daily water requirement @ 2 lt per Sqm #
|
154,00,000
|
lt
|
Yearly water requirement for 253 days (less rainy days 56*2)
|
38962,00,000
|
lt
|
Average area of each park
|
7,264
|
Sqm
|
Annual potential of Rainwater from each park with collection
efficiency of 75%
|
50,45,951
|
lt
|
Water requirement of each park per year
|
36,75,660
|
lt
|
Cost of rainwater harvesting per park (@ Rs 125000=00 for 2500 Sqm)
|
3,63,208
|
Rs
|
# BBMP Bangalore is promoting tree based parks (less of lawn) and
organic manure for plants
|
