4. History
Around the third century BC, the farming
communities in Baluchistan (in present
day Pakistan, Afghanistan and Iran), and Kutch
(in present-day India) used rainwater harvesting
for irrigation.
Karez in Baluchistan
5. Rainwater Harvesting - Definition
Accumulating and storing of rainwater for reuse
before it reaches the aquifer.
Used to provide drinking water, water for
livestock, water for irrigation, as well as other
typical uses.
Rainwater collected from the roofs of houses
and local institutions can make an important
contribution to the availability of drinking water.
6. The climate in Pakistan
Pakistan is a predominantly dry country. The flat
areas in the south and centre have a desert-like
climate. May and June are the hottest months, when
it is 40 to 45 °C. The best travel period is from
December to March, when it is relatively cool. The
north of the country is visited by the monsoon in
July and August. In a short space of time a lot of
rain can fall and there can be heavy storms.
7. Importance of RWH in Punjab
The north Punjab areas Rawalpindi, Attock,
Jhelum and Chakwal natives rely on water
sources from rainfall and ground water. Pakistan
is known as an arid country having subtropical
climate and it may be divided into two regions.
1. Indus plain
2. Highlands
8. Dry climate is dominant in most of the country
parts except northern highlands. On an average
about 750mm of rain fall occurs annually in
northern areas. Baluchistan receives about
250mm of rainfall annually.
There is dire need to address the water shortage
issues across the country.
9. Need For Rainfall Harvesting in Urban
Areas of Punjab
Groundwater reservoirs have been declining in
urban areas due to rapid urbanization.
Excessive use of groundwater is causing
deterioration of water quality and drying up of
water wells.
The sweet water becoming scarce in urban
areas of Punjab Province.
Up-coning of deep saline water has started in
some parts of Punjab.
10. Name of city Faisalabad
Population( million) 2.83
11. There is a need to realistically estimate and
manage water resources for sustainable
development.
Storage of rain water on surface for future
use.
Recharge to ground water for sustainable
water supply in urban areas.
12. Rainwater harvesting techniques
There may be two rainwater harvesting
techniques for the accumulation of rainwater
that may be used for different purposes.
1. Land-based.
2. Roof-based.
13. Land-based
When the infiltration requirements of the soil have
been fulfilled and excess amount of rainwater flow
as overland flow and then become the runoff and this
runoff accumulated in reservoirs for agriculture
growth purposes, in ponds for recharging purposes
and in tanks for household, this type of rainwater
harvesting technique is called land-base.
14. Roof-based
The rainwater that falls on the top of the roof is
harvested for a domestic purpose, small scale
agriculture purposes and is also sometimes used
for drinking water because this water is usually
collected from clean surfaces. This type of water
harvesting is called roof-based water harvesting.
16. Factors affecting RWH system design
Rainfall quantity (mm/year)
Rainfall pattern
Collection surface area (m2)
Runoff coefficient of collection (-)
Storage capacity (m3)
Daily consumption rate (liters/capita /day)
Number of users
Cost
Alternative water sources
17.
18. RWH System Components
Catchment Area/Roof
- the surface upon which the rain falls
Gutters and Downpipes
- the transport channels from catchment
surface to storage
Leaf Screens and Roof washers
- the systems that remove contaminants and
debris
19. Cisterns or Storage Tanks
- where collected rainwater is stored
Conveying
- the delivery system for the treated rainwater,
either by gravity or pump
Water Treatment
- filters and equipment, and additives to
settle, filter, and disinfect
20.
21. Design considerations for rooftop
catchment systems
The material of the catchment surfaces must be
non-toxic and not contain substances which impair
water quality.
Roof surfaces should be smooth, hard and dense
since they are easy to clean and are less likely to
be damaged and shed materials into water.
Precautions are required to prevent the entry of
contaminants into the storage tanks.
22. No overhanging tree should be left near the
roof.
All gutter ends should be fitted with a wire
mesh screen to keep out leaves.
The storage tank should have a tight-fitting roof
that excludes light, a manhole cover and a
flushing pipe at the base of the tank.
The nesting of the birds on the roof should be
prevented.
23. A sloped bottom and a provision of a sump
and a drain are useful for collection and
discharge of settled grit and sediment.
Taps/faucets should be installed at 10 cm
above the base of the tank as this allows any
debris entering the tank to settle on the bottom
where it remains undisturbed, will not affect
the quality of water.
24. Design Consideration
An estimate of mean annual runoff from a given
catchment can be obtained using the equation.
S = R * A * C
Where
S = Rainwater supply per annum
R = mean annual rainfall
A = Area of the catchment
C = Runoff coefficient
Mean annual runoff
25. Catchment Area Size
Runoff depends upon the area and type of the
catchment over which it falls as well as surface
features.
Runoff coefficient for any catchment is the ratio of
the volume of water that runs off a surface to the
volume of rainfall that falls on the surface.
(C = V1/V2)
Type of Catchment Coefficients
Tiles 0.8 – 0.9
Corrugated metal sheets 0.7 – 0.9
26. Storage System
There are several options available for the storage
of rainwater. A variety of materials and different
shapes of the vessels have been used. In general,
there can be two basic types of storage system.
Underground tank or storage vessel
Ground tank or storage vessel
27. The choice of the system will depend on several
technical and economic considerations like, space
availability, materials and skill available, costs of
buying a new tank or construction on site, ground
conditions, local traditions for water storage etc.
Selection of System
28. Storage capacity
Knowledge of the rainfall quantity and
seasonality, the area of the catchment surface
and volume of the storage tank, and quantity
and period of use required for water supply
purposes is critical.
29. A better estimate of storage requirement can be
made using the mass curve technique based on
rainfall and water demand pattern.
Cumulative rainfall runoff and cumulative water
demand in year is calculated and plotted on the
same curve.
The sum of the maximum differences, on the
either side, between the rainfall curve and water
demand curve gives the size of the storage required.
39. THE RAINXCHANGE™ SYSTEM
The Aquascape RainXchange™ Harvesting
Systems are a revolutionary design that combines a
recirculating decorative water feature with a sub-
surface rainwater harvesting collection system.
Clean, Filtered Water Collection & Storage
While you enjoy the benefits of a decorative water
feature, the RainXchange™ Rainwater Harvesting
System filters the stored water to prevent
stagnation and growth of unhealthy bacteria.
40. The RainXchange™ Rainwater Harvesting
System reveals only a beautiful water
feature that integrates easily into existing
landscape.
Collecting and storing the water
underground maintains the integrity and beauty
of your home and landscape.
