Rain water harvesting is the process of collecting, conveying, and storing rainwater for beneficial uses such as drinking water and irrigation. It helps address issues of temporal and spatial variation in water availability. The basic components are precipitation collection, water storage, and distribution. Rainwater harvesting has multiple purposes including increasing agricultural water supply, human consumption, groundwater recharge, reducing urban floods and loads on sewage systems. Methods include direct use storage tanks, rooftop runoff recharge into groundwater, and surface runoff recharge into aquifers using techniques like abandoned wells or sand filters. It provides advantages like self-sufficiency, lower costs, improved water quality, reduced soil erosion, and flood mitigation.

1. RAIN WATER HARVESTING
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2. INTRODUCTION
• Rain Water Harvesting – process of collecting,
conveying & storing water from rainfall in an
area for beneficial use.
• Storage – in tanks, reservoirs, underground
storage groundwater
• Necessity - Temporal & spatial variation of
rainfall & water availability

3. World Water Balance (WWB)
Total water distributed on earth = 1386Mkm cube
similar 1400 Mkm cube
97.5% ocean saline
2.5% that is35Mkm cube
 10.6 Mkm cube - liquid
 24.4 Mkm cube - frogen
About ¾ of earth is covered by water

4. Basic Components Of RWH
• Precipitation
• Collection of water from surface catchment
• Water storage
• Distribution of water

5. Water Demand

6. Comparative Graph Of Monthly
Demand And Runoff

7. Purposes of Rainwater Harvesting
• Two Major Purposes: Agricultural and human
consumption
• Increase groundwater recharge
• Reduce storm water discharges,
• urban floods and overloading of sewage
treatment plants
• Reduce seawater ingress in coastal areas

9. Rainwater Harvesting - Methodologies
• Storing rain water for direct use
• Recharging ground water aquifers from roof
top run off
• Recharging ground water aquifers with runoff
from ground areas

10. 1. Storing Rain Water For Direct Use

11. 2. Recharging Ground Water
Aquifers From Roof Top Run Off

12. 3. Recharging ground water aquifers
with runoff from ground areas

13. Methods of recharging subsurface aquifers
• Recharge through abandoned hand pump.

14. • Recharge through abandoned dug well/open
well

18. Sand filter

20. characteristics for drinking water

21. Advantages
• Provides self-sufficiency to water supply
• Reduces the cost for pumping of groundwater
• Provides high quality water, soft and low in minerals
• Improves the quality of ground water through dilution
when recharged to groundwater
• Reduces soil erosion in urban areas
• Rooftop rain water harvesting is less expensive
• Rainwater harvesting systems are simple which can be
adopted by individuals
• Rooftop rain water harvesting systems are easy to
construct, operate and maintain.