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Rainwater harvesting- 2 case studies


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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.

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Rainwater harvesting- 2 case studies

  1. 1. Rainwater Harvesting In India A rural and urban case study S.Vishwanath
  2. 2. In a water scarce world we need to conserve every drop of water Photo : Norma Angelica Hernandez Bernal
  3. 3. Rainwater harvesting <ul><li>Collecting and storing rainwater for future productive use. Storing can also be in aquifers through artificial recharge systems </li></ul><ul><li>A rainwater harvesting system consists of catchment , conveyance, filtration and storage or recharge structure. </li></ul>
  4. 4. India- Policy recognition for rainwater harvesting <ul><li>The National Water Policy and the State Water Policy recognize the role of rainwater harvesting </li></ul><ul><li>.. 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. </li></ul><ul><li>Source : </li></ul>
  5. 5. Rural rainwater harvesting <ul><li>Rainwater from rooftops is collected in above the ground brick masonry tanks of 2000 litres capacity each in a 1000 villages </li></ul><ul><li>Rainwater harvesting has been implemented in 23683 schools in rural Karnataka State </li></ul><ul><li>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. </li></ul>
  6. 6. A simple traditional rainwater harvesting system
  7. 7. An above the ground rainwater 2000 litre rainwater storage tank
  8. 8. Quality check- using the H2S vial test for e.coli identification Put sample water in bottle and observe for 36 hours Brown colour indicates no e-coli, black water would indicate e-coli
  9. 9. Simple treatment for e-coli in rainwater using SODIS Keep water in a bottle for 5 hours in the sun
  10. 10. Rainwater harvesting in Bangalore city <ul><li>At the city level rainwater is collected in many lakes and allowed to infiltrate and recharge the groundwater </li></ul><ul><li>At individual buildings, rainwater is harvested either by storing in sump tanks or by recharging through small wells. </li></ul>
  11. 12. Local hydrologic cycle – seeking bio mimicry with rainwater harvesting
  12. 13. Hydro-flows from a small plot <ul><ul><ul><li>Before building After building </li></ul></ul></ul><ul><li>Surface runoff 15 % 90% </li></ul><ul><li>Recharge 10 % 5% </li></ul><ul><li>Evapo-transpiration 75 % 5% </li></ul><ul><li>The aim of rainwater harvesting is bio-mimicry. To restore the local hydrology on a plot as before building </li></ul>
  13. 14. A rain barrel is the simplest way to harvest rainwater
  14. 15. The new rainwater harvesting bye-law for Bangalore City <ul><li>For every plot create recharge or storage </li></ul><ul><ul><li>@ 20 litres per square metre of roof area </li></ul></ul><ul><ul><li>@ 10 litres per square metre of paved area </li></ul></ul><ul><ul><li>Minimum depth of recharge well 3 metres </li></ul></ul>
  15. 16. How to harvest rainwater ? <ul><li>Understand rain (quantum/pattern/intensity) </li></ul><ul><li>Cascade capture </li></ul><ul><li>House/Apartment/Institution/Industry/Park </li></ul><ul><li>Storm water harvesting in ‘tanks’/lakes </li></ul><ul><li>Ground water recharge </li></ul>
  16. 17. Rainfall pattern in Bangalore Maximum rainfall intensity 90 mm/hour 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
  18. 19. Rainwater harvesting in an underground tank
  19. 20. A first rain separator and a sand filter
  20. 21. Harvested rainwater in underground tank
  21. 22. Site identification FOR RECHARGE with rainwater The site should have a sufficient clean and large catchment. It should also permit fast infiltration and percolation.
  22. 23. Excavation The excavation should reach porous soil / weathered rock / fracture. Digging the pit
  23. 24. Back-filling. Round hard stones Smaller stones on top Filling of the recharge pit with large stones first than small stones
  24. 25. Finished recharge pit with coarse sand filling over the small stones
  25. 26. Recharge pit around bore wells
  26. 27. 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
  27. 28. Recharge wells details Silt and leaves trap in a storm-water drain Covers : steel grill or perforated RCC
  28. 29. Rainwater going inside a recharge well Re-charging a bore well Outlet pipe in recharge well
  29. 30. Procedure <ul><li>Locate recharge well in the storm water channel or just off the channel </li></ul><ul><li>Make arrangements to remove silt and leaves before water enters recharge well </li></ul><ul><li>Monitor the rate of recharge and decide on the number of recharge wells necessary for the catchment </li></ul>
  30. 31. Don’t forget the maintenance
  31. 32. Recharge wells in storm-water drains
  32. 33. A landscaped recharge well in an office
  33. 34. We need rainwater harvesting for the Blue Planet Every drop counts