This is a talk given at an Engineer Association meet on the role of rainwater harvesting in rural and urban areas in the current context of India's water situation.

1. Urban water management in India
The role of rainwater harvesting
Case studies and technical feasibilities

7. Groundwater
• India has the single largest exploitation of
groundwater in the world with over 20
million bore-wells
• 65 % of the net irrigated land gets water
from bore-wells
• 85 % of rural habitations depend on
groundwater

9. Photo : Norma Angelica Hernandez Bernal

10. Rainwater harvesting
• Collecting and storing rainwater for future
productive use.
• System consists of catchment ,
conveyance, filtration and storage

17. The issue
• Exploding water demand in cities
• Problems of urbanization : water shortage and flooding
• Need to manage water in cities holistically
Case study of a city as an example

18. • 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

19. Law of the jungle

20. Old forest release water or do they?

21. The Cauvery river basin Bangalore

22. Bangalore need
Bangalore
Bangalore gets its water from the Cauvery 95 kms and 500 meters below the city

23. Water in the city
Lakes and tanks :
261 in 1960
81 in 1997
55 in 2000
Lake development authority created to
preserve and enhance surface water
bodies in city

24. Bangalore need : limitations
• Production cost of water is very high at Rs 18/ ( Rs23.47)- a kilo-liter. It will
become Rs 26/- a kilo-liter.
• Ceiling on the availability : 1,500 mld. Good enough for 7 million people only
i.e. by the year 2011.
• Surface and groundwater on the decline.

25. 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

27. The new rwh bye-law
• 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

28. Local hydrologic cycle

29. Hydro-flows
• Surface runoff 15 90
• Recharge 10 5
• Evapo-transpiration 75 5
• The aim of rainwater harvesting is bio-
mimicry.

30. How much water do I use ?
Use Litres/person
Drinking 3
Cooking 4
Bathing 20
Flushing 40
Washing-clothes 25
Washing Utensils 20
Gardening 23
Total 135
Consumption range :
from 50 to 300 liters per person per day

31. What is rainwater harvesting ?
The collection and storage of rain for future productive use

32. Capital cost – in Bangalore
• Piped water supply :
1,500 Million Litres per Day
Investment Rs.60,000 million ($ 1500 million)
• Rainwater :
3,000 Million Litres per Day
Rs. “0.00”(zero) ?
Can a better balance be reached ??

33. 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

34. 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

35. EVERY ROOF CAN BE A CATCHMENT

36. Gutters
Gutter-for sloping roof transmitted through
- PVC
- Polycarbonate
- GI
- Aluminium
- Stainless steel
PVC GUTTER

37. Downpipes
Down water pipes made of
- HDPE
- PVC
-AC PIPES ARE OK TOO

40. Double drums filter
When the roof area is bigger than 100 m², it is possible to use two drums as filter.
Drum filter of the roof top harvesting system of an appartment
Collecting pipes
from the roof
Overflow pipe to
the recharge well
Pipe to the sump
tank

41. Water harvesting and water reuse in a house

42. Rain barrel : easiest way to begin rainwater harvesting

43. Rain barrels at work

44. Details of a rain barrel
Aluminium basket filter
Plastic basket filter

45. Rainwater harvesting in an industry
4 acres > objective 0% runoff
Rain Barrels harvesting rooftop rainwater

46. .

50. Site Selection for Infiltration
Many factors affect the suitability of a site as an infiltration facility for the
disposal of stormwater. Among these, the following are most important:
• Depth to groundwater
• Surface soil type
• Underlying soil type
• Vegetation cover of the infiltrating surface
• The uses of the infiltrating surfaces
• The ratio of tributary impervious surface to the infiltrating surface

51. If the pit aims to recharge a borewell, it should be built as close to it as possible.
Ideally it should be in the valley of the surface layout.
The making of a recharge pit : locality
Borewell and recharge pit

52. Site identification
The site should have a sufficient clean and large catchment.
It should also permit fast infiltration and percolation.

53. Excavation
The excavation should reach porous soil / weathered rock / fracture.
Digging the pit

54. Backfilling. Round hard material. Smaller stones on top
Filling of the pit

55. Finished recharge pit

56. Recharge pit around bore wells

57. The pit has reach the silt layer
Pit and concrete rings
Placing of the rings
The making of a recharge well

58. Recharge wells details
Silt and leaves trap in a stormwater drain
Covers : grilled or
perforated RCC

59. Rainwater sent for recharge
Recharging a bore well
Outlet pipe in recharge well

60. Procedure ….. continued
• Locate recharge well in the channel or 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

61. Don’t forget the maintenance

63. Chikkabettahalli ..
...and provides for
the poor

65. Stormwater collected into a sump and used for the garden
> 10 lakhs litres of water stored every year

66. Increasing soil moisture
Swales

67. The storm drain
keep it clean make a recharge well

68. The electric line put conduits on electric lines

70. The road address road cutting
prevent damage
Keep an eye on the contractors work

71. The roadside trees
Make saplings, Plant trees,Take care of them

72. Roofs and Terraces.............

73. Most of the time are
• Sterile,
• Uninteresting
and
• Heat sinks

74. Roof
• 100 sq. mt. 100,000 litres of water
• 100 sq. mt 200 kgs of rice and vegetables
• 100 sq. mt. All the grey water –100 ltrs/day
• 100 sq.mt All the urine 1500 litres / year
• 100 sq. mt All the solid waste generated
• 100 sq mt 32 different species of birds
• 100 SQ mt heat 100 litres daily
• Light 12 bulbs
• Cook for 4 people lunch and dinner

75. Can they be smarter ????
– Since they receive----------
– maximum sunlight and heat
– all the rain
– lots of wind and
– a whole bunch of birds, butterflies and bees
– Can they solve Bangalore’s water, wastewater, energy,
sewage, food and bio-diversity problem ?

76. Can they be smarter ????
– Since they receive----------
– maximum sunlight and heat
– all the rain
– lots of wind and
– a whole bunch of birds, butterflies and bees
– Can they solve Bangalore’s water,
wastewater, energy, sewage, food and bio-
diversity problem ?

77. How about?
A roof that grows rice

80. So what can a smart roof do?
• Provide
– Food security… and grow rice, banana,
vegetables
– Water security .. and treat waste water
– Energy security… and keep the house cool
– Ecological security… and help save the
sparrow

81. Harvests rain

82. Uses the Sun

83. Uses treated grey water to grow it

84. Where do the children play?

85. 2007 – moved out
2005 GOOGLE IMAGE 2007 GOOGLE IMAGE

86. 2009 – nowhere to go

87. No pavement, no play space
But barbed wire and parking

88. thankyou