S.Vishwanath
www.rainwaterclub.org
Twitter handle : zenrainman
Rainwater harvesting systems
Water Era in India� Rainwater + shallow aquifer < 1850
� Surface water + shallow aquifer+ rainwater 1850 - 1970
� Deep aquifer + surface water + rainwater 1970 --2015
� Rainwater + ….+… 2015 >
Rainwater harvesting� The method of collecting rainwater from purpose built catchments….. so for example rooftop rainwater harvesting…
Photo courtesy: Shree Padre
� Catchment
� Conveyance
� Filtration
� Storage
Good clean rainwater with a clean catchment and a good filter
The rainwater tank is a great place to do homework
..and is multipurpose , other waters can be stored. Storage is and is multipurpose , other waters can be stored. Storage is and is multipurpose , other waters can be stored. Storage is and is multipurpose , other waters can be stored. Storage is
access in areas of intermittent availabilityaccess in areas of intermittent availabilityaccess in areas of intermittent availabilityaccess in areas of intermittent availability Rooftop Rainwater harvesting is especially relevant in
Fluoride and Arsenic affected areas
� The ‘Sachetana’ project of the Government of Karnataka has put 10000 rainwater tanks in households across 105 villages. This provides drinking and cooking water for the whole year.
� The tank size is between 5000 litres and 8000 litres.
� It provides 20 litres of water per day per family for the whole year.
A ‘Sachetana’ rainwater harvesting system with details
painted on the wall
An above the ground storage tank RWH during Floods
RWH During non-flood situationQuality check- using the H2S strip test for e.coli
identification
Simple treatment using SODIS www.sodis.ch Urban Water and Sanitation
�The urban water footprint is increasing
Cities search for water
�Chennai: 235 km (Veeranam lake) and now planning to go farther 300 Km (Veeranam extension project).
�Bangalore: 95 km (Cauvery) pumping 300 m elevation.
�Delhi: from Tehri dam (450 km)
(Thanks to Gita Kavarana ).
Chennai
Veeranam
lake
Map of Tamil Nadu
Manjira dam
Hyderabad
Nagurjuna
105 km
100 km
Himayat Sagar
Osman Sagar
Vaitarna cum Tansa
90 km
105 km
Mumbai
Bhatsa
Narmada river
70 km
30 km
INDORE
INDORE
YASHWANT SAGAR
Indira Gandh
i canal
204 km
Rajivgandhi lift canal
Jodhpur
JODHPUR
The issue
• Exploding water demand in cities• Problems of urbanization : water shortage and flooding• Need to manage water in cities holistically
• New paradigm required
• Multiple sourcing of water
• Source control for flood management
• Institutional coordination
• People’s participation in solution’s
• More space for ‘softer’ solutions like education
Realities
Water tanker Bore well
With very little catchment management
Water in the city
Lakes and tanks :261 in 196081 in 199755 in 2000
Lake development authority created to preserve and enhance surface water bodies in city
Why harvest rainwater ?
• Provides supplemental water for city
• Recharges groundwater potential lost due to urban ‘crusting’
• Reduce ecological footprint of water (power/water nexus)
• Helps manage urban floods
• Prevents salinity ingress in coastal area
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
30 years data
Local hydrologic cycle – seeking bio mimicry with rainwater harvesting
Hydro-flows� Surface runoff 15 90
� Recharge 10 5
� Evapo-transpiration 75 5
� The aim of rainwater harvesting is bio-mimicry.
Rain barrel : easiest way to begin rainwater harvesting Details of a rain barrel
Aluminium basket filter
Plastic basket filter
.
Rain barrels at work
Rainwater harvesting in an industry
4 acres > objective 0% runoff
Rain Barrels harvesting rooftop rainwater
EVERY ROOF CAN BE A CATCHMENT
The new rainwater harvesting byeThe new rainwater harvesting byeThe new rainwater harvesting byeThe new rainwater harvesting bye----lawlawlawlaw
� By December 31st 2011 …� 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
About 50,000 buildings now have rainwater harvesting ..another 50,000 expected by year end.
Aerial View of Theme Park•Training for young plumbers
Creating groundwater banks – the use of the aquifer.A good hydro-geological study a prerequisite for artificial recharge using harvested rainwater
The other key objective of rainwater
harvesting is to keep the 500,000
bore-wells with a sunk cost of Rs 5000
crores alive and well
Excavation
The excavation should reach porous soil / weathered rock / fracture.
Digging the pit
Backfilling. Round hard material. Smaller stones on top
Filling of the pit Finished recharge pit
The pit has reach the silt layer
Pit and concrete rings
Placing of the rings
The making of a recharge well
Don’t forget the maintenance
Recharge wells in storm-water drains
Reflective paints but also potable rainwater A flourishing rainwater filter market
And a technology that helps
Reserving 5 % of any space for water
From a plot to the city