Rainwater harvesting

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Rainwater harvesting

  1. 1. Rainwater harvesting
  2. 2. What is rain water harvesting <ul><li>The collection and storage of rain water for </li></ul><ul><li>later productive use is defined as rainwater harvesting </li></ul>
  3. 3. How? Recharge if there’s excess The concept is simple Collect Store Use
  4. 4. Components of roof top rainwater harvesting <ul><li>Any rainwater harvesting system has three components </li></ul><ul><li>Catchment </li></ul><ul><li>Conveyance </li></ul><ul><li>Filters </li></ul><ul><li>Storage </li></ul>
  5. 5. ROOFTOP RAINWATER HARVESTING Catchment – rooftop Transportation – Down take pipes <ul><li>Filters – First flush device </li></ul><ul><ul><li>Leaf and grit filter </li></ul></ul>Storage – Tank / well Components
  6. 7. <ul><li>Catchment </li></ul><ul><li>Rooftops are favoured because of the large coefficient of run-off generated from them and relatively less likelihood of their contamination. </li></ul><ul><li>Conveyance </li></ul><ul><li>rooftops rainwater gutters and rainwater down pipes are conveyance systems </li></ul>
  7. 8. <ul><li>Storage </li></ul><ul><li>From the simplest ground level tank, surface lined ponds and large lakes storage options are many depending on the context of the rainwater harvesting design. </li></ul>
  8. 9. Catchment
  9. 10. The water that leaves the rooftop may be 65 – 90% of the water that falls on it Roof material absorbs some water More water loss if roof is flat Evaporation losses
  10. 11. Keep the roof clean <ul><li>Remove leaves, plant debris, bird and animal droppings, dead rodents or birds </li></ul><ul><li>No tar / bitumen on the roof </li></ul><ul><li>No chemical pesticides or fertilizers for rooftop garden </li></ul>
  11. 12. Conveyance
  12. 13. How much water can we harvest? Rain Water Collected From Both Sides of the Roof W Rain Water Collected From one Side of the Roof Amount of rainfall (mm) x = W Catchment Area (m2) Volume of water received (Litres)
  13. 14. Transportation Pipe size is calculated based on peak flow rates (rooftop area and peak rainfall rate) Gutter (open on top) Downtake pipe (cylindrical) PVC pipes preferred. Do not use lead pipes
  14. 15. Take care…. <ul><li>Clamp gutters and down take pipes well </li></ul><ul><li>Keep gutters clean of leaves </li></ul><ul><li>See that leaves do not clog a down take pipe </li></ul><ul><li>(Jaali or leaf filter may be needed at rooftop discharge point but this may also be a problem if leaf debris collects on it and water stagnates on the roof) </li></ul><ul><li>Gutters and down take pipes should be gently sloping towards the storage tank, so that there is no stagnation of water in the pipe </li></ul>
  15. 16. Filters
  16. 17. Filters Gravel Sand Inlet Out flow Over flow Gravel Recharge tank Filter Storage tank Down take pipes First flush Check and clean filters before and after each rainy season Make your own filter with sand, charcoal and gravel Or Buy a filter off the shelf
  17. 18. First flush <ul><li>The first rain carries with it a lot of filth from the rooftop and dissolved air pollutants </li></ul><ul><li>This rainwater should be diverted away from the storage tank using a first flush device. </li></ul><ul><li>Some filters have a first flush system integrated in them </li></ul><ul><li>Check and clean first flush devices regularly. </li></ul>First flush standpipe
  18. 21. Storage
  19. 22. Storage tank features <ul><li>Durable and no leaks </li></ul><ul><li>Built on a strong and stable substrate that can support the tank filled with water </li></ul><ul><li>Opaque – presence of light can cause algal growth in tank </li></ul><ul><li>Secure and impervious cover </li></ul><ul><li>Vents to be covered with insect proof mesh </li></ul><ul><li>Located as close as possible to demand and supply points to reduce plumbing </li></ul>
  20. 23. Storage tank features <ul><li>Overflow pipe should be provided close to the top, to reduce dead space. </li></ul><ul><li>Overflow pipe diameter should be equal to inlet pipe diameter </li></ul><ul><li>Overflow pipe should lead excess water away from the foundation of tank and other buildings. </li></ul><ul><li>Preferably the overflow should be led into a groundwater recharge system or a garden </li></ul><ul><li>There will be sedimentation in the tank. Taps and pipes to draw water from the tank should </li></ul><ul><li>not be very close to the bottom to prevent sediments from entering the plumbing system </li></ul><ul><li>and clogging it. </li></ul>
  21. 24. What can we use the rain water for? If used for drinking, it is absolutely necessary to check water quality in a lab and treat as required
  22. 25. Other factors <ul><li>Some changes may be required in plumbing, if retrofit </li></ul><ul><li>Clean rwh system regularly </li></ul><ul><ul><li>Rooftop everyday </li></ul></ul><ul><ul><li>Tank after a rainy season </li></ul></ul><ul><ul><li>Filter after a rainy season </li></ul></ul>
  23. 26. Rainwater Harvesting <ul><li>DO </li></ul><ul><li>IT </li></ul><ul><li>NOW! </li></ul>
  24. 27. Why? <ul><li>At the city level </li></ul><ul><ul><li>Reduces water demand </li></ul></ul><ul><ul><li>Reduces energy demand – lesser energy required for water distribution </li></ul></ul><ul><ul><li>Improves groundwater situation </li></ul></ul><ul><ul><li>In coastal areas, it can counter saline water intrusion into freshwater aquifers </li></ul></ul><ul><ul><li>Prevents urban flooding </li></ul></ul>
  25. 28. Why? <ul><li>At the school level </li></ul><ul><li>Reduces water bills </li></ul><ul><li>Sets an example for students and parents </li></ul><ul><li>Improves groundwater table if rainwater is recharged </li></ul><ul><li>Improves groundwater quality by dilution </li></ul><ul><li>(rainwater has nearly neutral pH and zero hardness) </li></ul>
  26. 29. ROOFTOP RAINWATER HARVESTING Catchment – rooftop Transportation – Down take pipes <ul><li>Filters – First flush device </li></ul><ul><ul><li>Leaf and grit filter </li></ul></ul>Storage – Tank / well Components
  27. 30. How much water can we harvest? Rain Water Collected From Both Sides of the Roof W Rain Water Collected From one Side of the Roof Amount of rainfall (mm) x = W Catchment Area (m2) Volume of water received (Litres)
  28. 31. Transportation Pipe size is calculated based on peak flow rates (rooftop area and peak rainfall rate) Gutter (open on top) Downtake pipe (cylindrical) PVC pipes preferred. Do not use lead pipes
  29. 32. Take care…. <ul><li>Clamp gutters and down take pipes well </li></ul><ul><li>Keep gutters clean of leaves </li></ul><ul><li>See that leaves do not clog a down take pipe </li></ul><ul><li>(Jaali or leaf filter may be needed at rooftop discharge point but this may also be a problem if leaf debris collects on it and water stagnates on the roof) </li></ul><ul><li>Gutters and down take pipes should be gently sloping towards the storage tank, so that there is no stagnation of water in the pipe </li></ul>
  30. 33. Filters http://www.rainyfilters.com/rainwater.aspx Gravel Sand Inlet Out flow Over flow Gravel Recharge tank Filter Storage tank Down take pipes First flush Check and clean filters before and after each rainy season Make your own filter with sand, charcoal and gravel Or Buy a filter off the shelf
  31. 34. First flush <ul><li>The first rain carries with it a lot of filth from the rooftop and dissolved air pollutants </li></ul><ul><li>This rainwater should be diverted away from the storage tank using a first flush device. </li></ul><ul><li>Some filters have a first flush system integrated in them </li></ul><ul><li>Check and clean first flush devices regularly. </li></ul>First flush standpipe
  32. 35. STORAGE SIZE <ul><li>Depends on </li></ul><ul><li>Rainwater availability </li></ul><ul><li>Water requirement </li></ul><ul><li>Budget (storage tank is most expensive part of (rwh system) </li></ul><ul><li>Available space and aesthetics </li></ul><ul><li>Excess water can be diverted into a groundwater recharge system </li></ul><ul><ul><li>Do a water audit to check water requirement. </li></ul></ul>
  33. 36. STORAGE <ul><li>Above ground </li></ul><ul><ul><li>Ground level or Intermediate floor level </li></ul></ul><ul><ul><li>Just below roof </li></ul></ul><ul><li>Below ground </li></ul>Save on pumping cost
  34. 37. Storage tank features <ul><li>Durable and no leaks </li></ul><ul><li>Built on a strong and stable substrate that can support the tank filled with water </li></ul><ul><li>Opaque – presence of light can cause algal growth in tank </li></ul><ul><li>Secure and impervious cover </li></ul><ul><li>Vents to be covered with insect proof mesh </li></ul><ul><li>Located as close as possible to demand and supply points to reduce plumbing </li></ul>
  35. 38. Storage tank features <ul><li>Overflow pipe should be provided close to the top, to reduce dead space. </li></ul><ul><li>Overflow pipe diameter should be equal to inlet pipe diameter </li></ul><ul><li>Overflow pipe should lead excess water away from the foundation of tank and other buildings. </li></ul><ul><li>Preferably the overflow should be led into a groundwater recharge system or a garden </li></ul><ul><li>There will be sedimentation in the tank. Taps and pipes to draw water from the tank should </li></ul><ul><li>not be very close to the bottom to prevent sediments from entering the plumbing system </li></ul><ul><li>and clogging it. </li></ul>
  36. 39. What can we use the rain water for? If used for drinking, it is absolutely necessary to check water quality in a lab and treat as required
  37. 40. Other factors <ul><li>Some changes may be required in plumbing, if retrofit </li></ul><ul><li>Clean rwh system regularly </li></ul><ul><ul><li>Rooftop everyday </li></ul></ul><ul><ul><li>Tank after a rainy season </li></ul></ul><ul><ul><li>Filter after a rainy season </li></ul></ul>
  38. 41. Rainwater Harvesting <ul><li>DO </li></ul><ul><li>IT </li></ul><ul><li>NOW! </li></ul>
  39. 42. Pre-implementation guide for schools Rooftop Rainwater Harvesting

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