storm water rain water harvesting shoratge of water advantages road surface run off open drains plans drawing pictures storm water program design consideration

1. Rain Water Harvesting
&
Storm Water

2. Rain Water Harvesting

3. Reasons of Shortage of Water
 Population increase
 Industrialization
 Urbanization
(a) Increase in per capita utilization
(b) Less peculation area
 In places where rain fed/ irrigation based crops
are cultivated through ground water
 Decrease in surface area of Lakes, talab, tanks
etc.

4.  Deforestation
(i) Less precipitation
(ii) Absence of Barriers
1. Rain drops checked by leaves of tree
2. Water slowly descends through twigs & trunk
3. Humus – acts as reservoir
4. Tiny creatures – helps percolation

5. Rain Water
 Rain water is the ultimate source of fresh
water
 Potential of rain to meet water demand is
tremendous
 Rain water harvesting helps to overcome
water scarcity
 To conserve ground water the aquifers must
be recharged with rain water
 Rain water harvesting is the ultimate answer

6. Why Rain water be harvested?
• To conserve & augment the storage of ground
water
• To reduce water table depletion
• To improve the quality of ground water
• To arrest sea water intrusion in coastal areas
• To avoid flood & water stagnation in urban
areas
• It is the activity of direct collection of rain water
• Rain water can be stored for direct use or can
be recharged into the ground water aquifer

9. The roof catchment are selectively
cleaner when compared to the ground
level catchment
 Losses from roof catchment are minimum
 Built & Maintained by local communities
 No Chemical contamination & only required
filtration
 Available at door step with least cost

10. The typical roof top rain water harvesting
system comprises
 Roof catchment
 Gutters
 Down pipe & first flushing pipe
 Filter Unit
 Storage Tank

11. Roof catchment
 The roof of the house is used as the
catchment for collecting rain water. The style
construction and material of the roof effect
its suitability as a catchment, Roofs made of
corrugated iron sheet , asbestos sheet, Tiles
or Concrete can be utilized for harvesting the
rain water

14. Gutters
 Gutters are channels fixed to the edges of
roof all around to collect & transport the
rainwater from the roof. Gutters can be
made in semi-circular and rectangular shape
with cement pipe, plain galvanized iron
sheet, PVC pipes, bamboos etc. Use of locally
available material reduce the overall cost of
the system.

17. Down Pipe
 It is the pipe which carries the rainwater
from the gutters to the filter & storage tank.
Down pipe is joined with the gutters at one
end & the other end is connected to the filter
unit of the storage tank. PVC or GI pipe of
50mm to 75mm (2 to”) are commonly used
for down pipe. Bamboo can be also used
wherever available and possible

21. First Flush Pipe
 Debris, dust & dirt collect on the roof during
non rainy periods when the first rain arrive. A
first flush system arrangement is made to
avoid the entering unwanted material into
the Filter media & storage tank. This is a
simple manually operated arrangement or
semi-automatic system with a valve below
the ‘T’ junction

24. Filter Unit
 The filter unit is a container or chamber filled
with filter media such as coarse sand, charcoal,
coconut fiber, pebbles & gravels to remove the
debris & dirt from water that enters the tank. The
filter unit is placed over the storage tank or
separately. It may be of Ferro cement filter unit,
Aluminum, Cement rings or Plastic bucket etc.
 There is another way of filtering the debris and
dust particles that come from the roof along with
rainwater is to use a fine cloth as filter media. The
cloth in 2 or 3 layers can be tied to the top of a
bucket or vessel with perforations at the bottom.

26. Storage Tank
 It is used to store the water that is collected from the
roof through filter. For small scale water storage
plastic buckets, jerry cans, clay or cement jars,
ceramic jars, drums may be used. For larger
quantities of water, the system will require a bigger
tank with cylindrical or rectangular or square in shape
constructed with Ferro cement or cement rings or
plain cement concrete or reinforced cement concrete
or brick or stone etc. The storage tank is provided
with a cover on the top to avoid the contamination of
water from external sources. The storage tank is
provided with pipe fixtures at appropriate places to
draw the water to clean the tank & to dispose of
extra water. A provision for keeping the vessel to
collect the water is to be made.

27. Size of Storage Tank
• Based on
– No. of person in the House hold
– Per capita water requirement
– No. of days for which water is required
Example
Total water requirement for a household with 5 family
members, period 1 day & 135 lpcd (Liters per capita
per day)
= 5x 1x 135
= 675 Liters
Water Tank Capacity = 1000lit

38. Rain Water Harvesting– AdvantagesRain Water Harvesting– Advantages
 Provides self-sufficiency to water supply
 Reduces the cost for pumping of ground water
 Provides high quality water, soft and low in minerals
 Improves the quality of ground water through dilution when
recharged
 Reduces soil erosion & flooding in urban areas
 The rooftop rain water harvesting is less expensive & easy to
construct, operate and maintain
 In desert, RWH only relief
 In saline or coastal areas & Islands, rain water provides good quality
water

40. Storm Water

41. It is a system ofIt is a system of
pipes laid belowpipes laid below
ground to carry awayground to carry away
rainwater from pavedrainwater from paved
areas and buildingareas and building
roofs.roofs.
Photos: Source: Internet websitePhotos: Source: Internet website

42. Road Surface run off:
 In the urban areas, the pavement and roads are generally of
impervious material like asphalt or concrete etc.
 These surfaces contributes sizeable amount of storm water
surface runoff.
 It is then collected in a chamber provided with C. I. or RCC
perforated cover to receive rain water.
 These chambers are supposed to be provided on either side
of the roads at the suitable intervals, all junctions and all
depressions.
Strom Water

43. While designing following points should be considered,
 The average value for cross fall for roads are 1 in 35 to 1 in
50 depending upon the type of surfacing.
 Where the longitudinal gradients is flatter than 1 in 200,
false gradients of between 1 in 120 and 1 in 200 is provided
between the chambers.
 Considering a false crown of about 50mm, the collection
chambers are provided at about 25m intervals.
 A general empirical spacing between two chambers is not
more than 150m.
 One chamber is provided for 200 Sq. Mt. impervious
catchment area.

44. 1. Open Drains:
 In small towns where it may not be possible to
have two different sewerage and storm water
drainage system, this system of surface drain is
adopted.
 Constructed on one side or both side of the streets
or roads.
 They carry discharge from bathrooms, kitchen,
washing places etc. as well as rainwater from
roofs, courtyards and open grounds.
 They do not carry discharge from latrines and
urinals

45.  Constructed in different shapes and sizes.
 Rectangular drains, Semicircular drains, V Shaped or Peg
top drains, U Shaped drains

46.  Rectangular: One disadvantage – self cleansing
velocity is not developed and some deposits take
place in drains. So should be large in size.
 Semicircular: Suitable for large as well as short
drains. Self cleansing capacity.
 V Shaped or Peg top drain: Most used, Most useful
for small and large discharges, Const. is difficult and
costly, Not common.
 U Shaped: Combination of rectangular and semi
circular drains. They are suitable for both type of
discharges.

47. Covered Drains:

53. Disposal of Rain / Storm / Surface – water:
 All courtyards are provided with one or more outlet through which
rainwater is allowed to pass to the storm water system.
 The public drain storm water system may either be combined,
partially combined or separate system.
 Preferable to have a separate system for sewage and storm water.
 The storm water thus collected is discharged conveniently to a
nearby stream or water house.
 The invert level of the outfall should generally be the same as the
normal water level in the water course.
 In some cases rainwater is collected in the courtyard and used for
gardening.
 These days terrace water harvesting is necessary for every building
and the water will be discharged within the ground.

54. Similar to sewerage collection systems except with the following
basic differences.
 The size of a system is usually 225mm and min. size of branch
is 150mm.
 Flatter slopes may be provided as compare to sewage
system.
 Slope of 1 in 500 for storm water is sufficient as compare to 1
in 100 for sewage system for 150mm dia. Pipe.
 RCC non pressure pipes with longer lengths of 2mts. are
preferred compare to stoneware pipes in sewerage.
 The chambers provided to collect rainwater from paved
areas are provided with frame and gratings.

55. Source: Internet websiteSource: Internet website

57. Design Considerations:
1. The quantity of storm water depends upon many factors such
as the intensity of rainfall, the catchment area, the nature and
the condition of the drainage area.
2. Following points should be considered while designing storm
water drainage schemes.
 The object of storm-water drainage is to collect, carry and
dispose, the rainwater collected.
 Rainfall statistics must be studied – meteorological
conditions, intensity and duration of rainfall.
 It is impracticable to guard against infrequent extreme
heavy rainfall in the form of cloudburst.
 But it is necessary to consider adverse conditions for
design.

58. 3. For rainwater collection and disposal three rates of intense
rainfall for three different degrees of risk considerations.
 50mm/hr - flat surface on which pounding can be
tolerated during an intense storm and for few min. after
storm.
 75mm/hr - flat surface on which pounding cannot
normally be tolerated.
 150mm/hr – pounding is expected to be cleared within
3 to 4 mins.
 In case of non availability of data
 75mm/hr for roof drainage area.
 50mm/hr for paved area.