This document discusses rainwater harvesting. It begins by explaining the water cycle and how rain is formed. It then discusses the key components of a rainwater harvesting system, which includes the catchment area, collection devices, conveyance systems, and storage tanks. The most common techniques are described as roof top rainwater harvesting and surface runoff harvesting. Advantages include reducing water usage and costs, while disadvantages include installation costs and potential for mosquito breeding. Facts provided include amounts of rainwater collected from roofs and how much water common appliances use.

1. RAIN WATER HARVESTING
ENVIRONMENT STUDIES

2. OUTLINES:
• Rain water
• Water cycle
• Rainwater Harvesting
• Components
• Rainwater Harvesting Techniques
• Advantages
• Disadvantages
• Water Facts
• Refrences

3. RAIN? HOW IS RAIN MADE?
• Rain is liquid water in the form of droplets that have condensed from
atmospheric water vapor and then precipitated—that is, become heavy
enough to fall under gravity
• When the sun shines, it heats the water in the rivers and seas.
• The water changes into water vapour. This water vapour rises up into the
sky.
• The water vapour cools into droplets and becomes a cloud.
• When there are too many droplets in the cloud, they fall towards the
ground as rain.

4. WATER CYCLE:
• Evaporation:
• Heat from the Sun causes water on Earth (in oceans, lakes etc) to evaporate (turn from liquid into gas)
and rise into the sky. This water vapor collects in the sky in the form of clouds.
• Condensation:
• As water vapor in the clouds cools down it becomes water again, this process is called condensation.
• Precipitation:
• Water falls from the sky in the form of rain, snow, hail, or sleet, this process is called precipitation.
• Collection:
• Oceans and lakes collect water that has fallen. Water evaporates into the sky again and the cycle
continues.

5. WATER CYCLE:
• Transpiration:
• In a process similar to sweating, plants lose water which is absorbed into the atmosphere much like
evaporation. The combination of evaporation and transpiration is known as evapotranspiration.
• Sublimation:
• It is possible for a solid to transform into a gas directly (without becoming a liquid). The most common
example of sublimation is dry ice (solid carbon dioxide) which sublimes at normal air temperature.
Under certain conditions snow and ice can also sublime.

7. RAIN WATER HARVESTING:
• It is the process of collecting and storing water for future
productive use.
• Commonly used systems are constructed of three
principal components; namely, the catchment area, the
collection device, and the conveyance system.

8. COMPONENTS:
• Catchment surface - rooftop or other raised solid surface. The best catchment systems have hard,
smooth surfaces such as metal roofs or concrete areas. The amount of water harvested depends on the
quantity of rainfall, and the size of the surface and the slope of the catchment area.
• Gutters and downspouts - also known as distribution systems that channel the water from the
catchment area to a holding container such as a barrel, cistern, planted area, etc.
• Leaf screens - a screen that removes or catches debris.
• Roof washers - a device that diverts the "first flush" of rain before it enters the storage tank. Most
rainwater suppliers recommend that the "first flush" of water is diverted to an outside area of the
storage system, since the catchment surface may accumulate bird droppings, debris and other
pollution.

10. COMPONENTS:
• Storage tanks - In general, the storage tank is the most expensive component of a rainwater harvesting
system. There are numerous types and styles of storage tanks available. Storage can be above-ground or
underground. Storage containers can be made from galvanized steel, wood, concrete, clay, plastic,
fiberglass, polyethylene, masonry, etc. Examples of above-ground storage include; cisterns, barrels,
tanks, garbage cans, above ground swimming pools, etc. Storage tank prices vary based on different
variables such as size, material and complexity. To inhibit the growth of algae, storage tanks should be
opaque and preferably placed away from direct sunlight. The tanks should also be placed close to the
areas of use and supply line to reduce the distance over which the water is delivered. Also consider
placing the storage at an elevated area to take advantage of gravity flow. The tank should always be
placed on a stable and level area to prevent it from leaning and possibly collapsing.
• Delivery systems - gravity-fed or pumped to the landscape or other end use areas.
• Purification/treatment system - needed for potable systems to make the water safe for human
consumption, filtration systems and certification requirements

11. RAINWATER HARVESTING TECHNIQUES:
• Roof top rainwater harvesting.
• Surface runoff harvesting.

12. ROOF TOP RAIN WATER HARVESTING:
• In rooftop harvesting, the roof becomes the catchments, and the
rainwater is collected from the roof of the house/building. It can either
be stored in a tank or diverted to artificial recharge system. This method
is less expensive and very effective and if implemented properly helps in
augmenting the ground water level of the area.

13. HOW TO HARVEST RAINWATER:
• Collect water from the rooftop.
• Draw it down from pipes.
• Filter the water.
• Store in a sump or tank for later use.
• Charge the groundwater through a soak pit.
• Lead the water into a well to increase
ground water content.

14. SURFACE RUNOFF HARVESTING:
• Harvesting of surface runoff and storage of the same into
reservoirs such as water pans makes it available for use
when required.
• In this method of collecting rainwater for irrigation, water
flowing along the ground during the rains will be collected
to a tank below the surface of the ground.

15. ADVANTAGES:
• Makes use of a natural resource and reduces flooding, storm water
runoff, erosion, and contamination of surface water with pesticides,
sediment, metals, and fertilizers
• Reduces the need for imported water
• Excellent source of water for landscape irrigation, with no chemicals
such as fluoride and chlorine, and no dissolved salts and minerals
from the soil
• Home systems can be relatively simple to install and operate May
reduce your water bill
• Promotes both water and energy conservation
• No filtration system required for landscape irrigation

16. DISADVANTAGES:
• Limited and uncertain local rainfall
• Can be costly to install - rainwater storage and delivery systems can
cost between $200 to $2,000+ depending on the size and
sophistication of the system
• The payback period varies depending on the size of storage and
complexity of the system
• Can take considerable amount of time to "pay for itself"
• Requires some technical skills to install and provide regular
maintenance
• If not installed correctly, may attract mosquitoes (i.e.; West Nile
Disease and other waterborne illnesses)
• Certain roof types may seep chemicals, pesticides, and other
pollutants into the water that can harm the plants
• Rainwater collected during the first rain season is generally not
needed by plants until the dry season. Once catchment is full, cannot
take advantage of future rains

17. DRINK IT:
• Though rainwater as it falls from the clouds is very
pure, it does pick up dirt, dust and bacteria once it falls
on the roof. It is very necessary to therefore check the
quality of the water before using it for consumption.
• Form of deactivating bacteria and making water fit for
consumption is called SODIS – Solar disinfection of
water.
• From the tap in the rainwater storage tank fill the
bottle to the mark provided. Close the cap tightly. Bring
the bottle back to a safe place in a room. Observe for
24 to 48 hours. If the water turns black in the bottle
then it is micro-biologically contaminated and requires
treatment before being used for drinking. If the water
color stays brown, then the water is fit for drinking.

18. WATER FACTS:
• Dishwashers are more water efficient and effective than hand washing.
• Washing machines use approximately 14% of domestic water
• A typical family uses 70,000 liters year on clothes washing, and outside
use
• Approximately 600 gallons of rainwater can be harvested from one
inch of rain falling on a 1,000 square foot roof.
• A leaky tap in the office toilets or canteen kitchen can waste 60 litres
an hour (5mm stream) or nearly half your daily usage.
• Rain is recycled water that evaporated from our world's lakes, rivers,
oceans, seas etc
• Rain occurs on other planets in our Solar System but it is different to
the rain we experience here on Earth. For example, rain on Venus is
made of sulfuric acid and due to the intense heat it evaporates before
it even reaches the surface!

19. THANK YOU!

20. References
• Wikipedia
• SlideShare
• YouTube
• Google