The presentation puts forward some examples of rooftop rainwater harvesting in rural and urban Karnataka State, India.
Rainwater harvesting is now part of policy at the National and State level. Cities are also making it mandatory to supplement water requirements
10. Indian Context: The “looming” crisis is now here Nation-wide 29% of the blocks are critical, semi-critical or over-exploited In some states as high as 75%
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12. Therefore the need to conserve every drop of rain Photo : Norma Angelica Hernandez Bernal
37. Bangalore need Bangalore Bangalore gets its water from the Cauvery 95 kms and 500 meters below the city
38. 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
44. How much water do I use in urban Bangalore? Consumption range : from 50 to 300 liters per person per day 135 Total 23 Gardening 20 Washing Utensils 25 Washing-clothes 40 Flushing 20 Bathing 4 Cooking 3 Drinking Litres/person Use
45. What is rainwater harvesting ? The collection and storage of rain for future productive use
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49. Rainfall pattern in Bangalore 30 years data 970.00 59.8 TOTAL 137.00 10.0 AUG 194.80 9.3 SEP 180.40 9.0 OCT 110.20 8.3 JUL 64.50 4.0 NOV 80.80 6.4 JUN 22.10 1.7 DEC 119.60 7.0 MAY 46.30 3.0 APR 4.40 0.4 MAR 7.20 0.5 FEB 2.70 0.2 JAN QUANTITY (mm) DAYS MONTH
55. 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
63. 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 : l ocality Borewell and recharge pit
64. Site identification The site should have a sufficient clean and large catchment. It should also permit fast infiltration and percolation.
Since 1975 Indian agriculture has emerged as the world’s largest user of groundwater (Shah, 2007) The lower # is 4X the annual public invetsment in irrrigation projects, and more than all expenditures in India on poverty alleviation and rural development programmes A typical gw dist in US has ~1000 users, in Asia 100,000 farmers (western US suffered more extensive depletion on GW and before anywhere else)
(not gwq or need for development) Concern: Rapid decline of groundwater levels in may regions =>focus on Irrigated agriculture (even when the concern is about RWS) C&C may be needed in select crisis situations, as well as large users or urban settings Futility of C&C slowly being realized, but still popular in many circles