Rain is liquid water in
RAIN? How is rain made? 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
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.
As water vapor in the clouds cools down it becomes water again, this
process is called condensation.
Water falls from the sky in the form of rain, snow, hail, or sleet, this
process is called precipitation.
Oceans and lakes collect water that has fallen. Water evaporates into
the sky again and the cycle continues.
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.
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.
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
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.
- 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.
- 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 aboveground 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.
Makes use of a natural resource and reduces flooding, storm water runoff,
erosion, and contamination of surface water with pesticides, sediment, metals,
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
Promotes both water and energy conservation
No filtration system required for landscape irrigation
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
•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
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 microbiologically
treatment before being used for drinking. If the
water color stays brown, then the water is fit for
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
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!