rainwater harvesting- 2 case studies
DESCRIPTION
This slide show depicts how rainwater harvesting has been accommodated in policy and legislation in India and specifically in the state of Karnataka. It gives example of projects in rural areas and in the city of Bangalore.TRANSCRIPT
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Rainwater Harvesting In IndiaA rural and urban case study
S.Vishwanathwww.rainwaterclub.org
www.ircsa.orgwww.youtube.com/zenrainman
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Photo : Norma Angelica Hernandez Bernal
In a water scarce world we need to conserve every drop of water
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Rainwater harvesting
• Collecting and storing rainwater for future productive use. Storing can also be in aquifers through artificial recharge systems
• A rainwater harvesting system consists of catchment , conveyance, filtration and storage or recharge structure.
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India- Policy recognition for rainwater harvesting
• The National Water Policy and the State Water Policy recognize the role of rainwater harvesting
• .. The efficiency of utilization of water will be improved and awareness about water as a scarce resource fostered. Rainwater harvesting and water conservation will be encouraged. Conservation consciousness will be promoted through education, regulation incentives and disincentives.
Source : http://waterresources.kar.nic.in/state_water_policy-2002.htm
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Rural rainwater harvesting
• Rainwater from rooftops is collected in above the ground brick masonry tanks of 2000 litres capacity each in a 1000 villages
• Rainwater harvesting has been implemented in 23683 schools in rural Karnataka State
• In Fluoride affected areas more than 6000 underground rainwater tanks of capacity 5000-8000 litres each has been built through Government funding to provide water at 20 litres a year for the whole year.
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A simple traditional rainwater harvesting system
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An above the ground rainwater 2000 litre rainwater storage tank
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Quality check- using the H2S vial test for e.coli identificationPut sample water in bottle and observe for 36 hours
Brown colour indicates no e-coli, black water would indicate e-coli
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Simple treatment for e-coli in rainwater using SODIS
Keep water in a bottle for 5 hours in the sun www.sodis.ch
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Rainwater harvesting in Bangalore city
• At the city level rainwater is collected in many lakes and allowed to infiltrate and recharge the groundwater
• At individual buildings, rainwater is harvested either by storing in sump tanks or by recharging through small wells.
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Local hydrologic cycle – seeking bio mimicry with rainwater harvesting
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Hydro-flows from a small plot
Before building After building
• Surface runoff 15 % 90%
• Recharge 10 % 5%
• Evapo-transpiration 75 % 5%
• The aim of rainwater harvesting is bio-mimicry. To restore the local hydrology on a plot as before building
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A rain barrel is the simplest way to harvest rainwater
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The new rainwater harvesting bye-law for Bangalore City
• For every plot create recharge or storage– @ 20 litres per square metre of roof area– @ 10 litres per square metre of paved area
Minimum depth of recharge well 3 metres
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How to harvest rainwater ?
• Understand rain (quantum/pattern/intensity)
• Cascade capture
• House/Apartment/Institution/Industry/Park
• Storm water harvesting in ‘tanks’/lakes
• Ground water recharge
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MONTH DAYS QUANTITY (mm)
JAN 0.2 2.70
FEB 0.5 7.20
MAR 0.4 4.40
APR 3.0 46.30
MAY 7.0 119.60
JUN 6.4 80.80
JUL 8.3 110.20
AUG 10.0 137.00
SEP 9.3 194.80
OCT 9.0 180.40
NOV 4.0 64.50
DEC 1.7 22.10
TOTAL 59.8 970.00
Rainfall pattern in Bangalore Maximum rainfall intensity 90 mm/hour
30 years data
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EVERY ROOF IN A CITY CAN BE A CATCHMENT
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Rainwater harvesting in an underground tank
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A first rain separator and a sand filter
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Harvested rainwater in underground tank
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Site identification FOR RECHARGE with rainwater
The site should have a sufficient clean and large catchment. It should also permit fast infiltration and percolation.
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Excavation
The excavation should reach porous soil / weathered rock / fracture.
Digging the pit
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Back-filling. Round hard stones Smaller stones on top
Filling of the recharge pit with large stones first than small stones
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Finished recharge pit with coarse sand filling over the small stones
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Recharge pit around bore wells
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The pit has reach the silt layer
Pit and concrete rings
Placing of the rings
The making of a recharge well – to put rooftop rainwater or stormwater into the aquifer. In Bangalore city, typically 6 metres deep and 1 metre diameter
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Recharge wells details
Silt and leaves trap in a storm-water drainCovers : steel grill or perforated RCC
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Rainwater going inside a recharge well
Re-charging a bore wellOutlet pipe in recharge well
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Procedure• Locate recharge well in the storm water
channel or just off the channel
• Make arrangements to remove silt and leaves before water enters recharge well
• Monitor the rate of recharge and decide on the number of recharge wells necessary for the catchment
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Don’t forget the maintenance
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Recharge wells in storm-water drains
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A landscaped recharge well in an office
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We need rainwater harvesting for the Blue Planet Every drop counts