Roof Top Rain Water Harvesting
What is Roof Top Rain Water Harvesting
Rooftop
Rain Water Harvesting is the technique through which rainwater is captured
from the roof catchments and stored in reservoirs. Harvested rainwater can be
stored in sub-surface groundwater reservoirs by adopting artificial recharge
techniques to meet the household needs through storage in tanks.
The
Main Objective of rooftop rainwater
harvesting is to make water available for future use. Capturing and storing
rainwater for use is particularly important in dry land, hilly, urban and
coastal areas. In alluvial areas, energy-saving for 1m.rise in groundwater
level is around 0.40-kilo watt per hour.
Need for Rooftop
Rain Water Harvesting
1.
To meet the ever-increasing demand for water
2.
To reduce the runoff which chokes storm drains
3.
To avoid flooding of roads
4.
To augment the groundwater storage and control the decline of water levels
5.
To reduce groundwater pollution
6.
To improve the quality of groundwater
7.
To reduce the soil erosion
8.
To supplement domestic water requirements during summer, drought, etc.
Advantages of Rain
Water Harvesting
1.
Provides self-sufficiency to your water supply
2.
Reduces the cost for pumping of groundwater
3.
Provides high-quality water, soft and low in minerals
4.
Improves the quality of groundwater through dilution when recharged to groundwater
5.
Reduces soil erosion in urban areas
6. Rooftop rainwater harvesting is less expensive
7.
Rainwater harvesting systems are simple which can be adopted by individuals
8.
Rooftop rainwater harvesting systems are easy to construct, operate, and
maintain
9.
In hilly terrains, rainwater harvesting is preferred
10.
In saline or coastal areas, rainwater provides good quality water and when
recharged to groundwater, it reduces salinity and also helps in maintaining a balance between the fresh-saline water interface.
11.
In Islands, due to the limited extent of freshwater aquifers, rainwater harvesting
is the most preferred source of water for domestic use
12.
In the desert, where rainfall is low, rainwater harvesting has been providing relief
to people
Safety
Consideration Storage in Ground Water Reservoir
1.
For rooftop rainwater harvesting through existing tube wells and hand pumps, a filter or desilting pit should be provided so that the wells are not silted.
2.
Such tubewells if pumped intermittently, increase the efficiency of recharge.
3.
If the groundwater reservoir is recharged through, shaft, dug well, etc., the inverted
filter may be provided.
Storage in Tanks
1.
A storage tank should not be located close to a source of contamination, such
as a septic tank, etc.
2.
A storage tank must be located on a lower level than the roof to ensure that it
fills completely.
3.
A rainwater system must include the installation of an overflow pipe which empties
into a non-flooding area. Excess water may also be used for recharging the
aquifer through a dug well or abandoned hand pump or tube well etc.
4.
A speed breaker plate must be provided below the inlet pipe in the filter so as not
to disturb the filtering material.
5.
Storage tanks should be accessible for cleaning.
6.
The inlet into the Storage tank should be screened in such a way that these can
be cleaned regularly.
7.
Water may be disinfected regularly before using for drinking purposes by chlorination
or boiling etc.
How Much You Can
Collect
Collection
Efficiency
How
efficiently the rainfall can be collected depends on several considerations.
Collection efficiencies of 80% are often used depending on the specific design.
Rainfall
Reliability
The
first step is to determine how much water would be generated from your roof
area. Average monsoon rainfall is used for this purpose.
Formula:
Total quantity of water to be collected (cu.m.) = Roof Top Area (Sq.m.) x Average Monsoon Rainfall (m) x 0.8
(2) (0)