Rainwater Harvesting

1. Rainwater Harvesting and
Watershed Management

3. Some Facts about Water
• Only 2.5% of the world’s water is freshwater and most of this are
in the form of polar ice-caps.
• Water use has increased by 70% since 1970
• A recent report by Credit Suisse stated that by 2025 18 countries
will experience water demand beyond supply capabilities
• It takes up to 5000 lt of water to produce 1kg of rice.
• Every square mile of developed land causes 16 million gallons of
rain water to directly enter the rivers on a rainy day!
• Each person uses about 150 litres of water every day. About 60
litres of this is for toilet flushing
• Toilet flushing is the single largest user of household water, 30-
40%, up to 90% for offices.

4. What is Water harvesting??
• Water harvesting is the capture, diversion,
and storage of water obtained from different
freshwater sources for plant irrigation,
domestic purposes, industrial purposes,
groundwater recharge and other uses.

5. Rainwater harvesting [RWH]
• It is a type of water harvesting.
• It can be defined as the system of collection
and concentration of rain water and its run
off and its productive use for :-
a) Irrigation of annual crops pastures and trees.
b) Domestic and livestock consumption.
c) Groundwater recharge.

6. Need For Rainwater Harvesting
• Major parts of our country have been facing continuous
failure of monsoon and consequent deficit of rainfall over the
last few years.
• Also, due to ever increasing population of India, the use of
ground water has increased drastically leading to constant
depletion of ground water level causing the wells and tube
wells to dry up.
• In some places, excessive heat waves during summer create a
situation similar to drought.
• It is imperative to take adequate measures to meet the
drinking water needs of the people in the country besides
irrigation and domestic needs.
• Out of 8760 hours in a year, most of the rain in India falls in
just 100 hours.

8. Rainwater can be harvested in a
variety of ways:
Rainwater can be harvested in a variety of ways:
• Directly from roof tops and stored in tanks.
• Monsoon run off and water in swollen streams
during the monsoon and storing it in
underground tanks.
• Water from flooded rivers can be stored in small
ponds.
• Collection and transfer of rainwater into
percolation tanks so as to facilitate discharge into
ground.

9. Components of RWH
Catchment
Delivery
Storage

10. Models of RWH
There are two main models of rainwater
harvesting done in India:-
• RURAL MODEL.
• URBAN MODEL.

11. Rural model of RWH
• Rural areas generally use traditional methods of
rainwater harvesting.
• Main motive of rainwater harvesting in these
areas is to facilitate irrigation for agriculture and
use of water for domestic and drinking purposes.
• Nowadays practices are also been followed to as
to recharge groundwater levels.
• Many of the traditional structures include
Tankas, Nadis, Talabs, Bavdis, Rapats, Kuis,
Virdas, Kunds, Khadins, Johads etc.

12. Bawodi
Traditional step wells
are called vavadi in
Gujarat, or baoris or
bavadis in Rajasthan
and northern India.
Kunds
Covered underground
tank, developed
primarily for tackling
drinking water
problems.

13. Khadin Bund

14. Urban Model of RWH
• More modernized system of rainwater
harvesting.
• The main components of the urban model are:-
a) Roof catchment
b) Gutters
c) Down pipe
d) First flush pipe
e) Filter unit
f) Storage tank
g) Collection pit.

15. Components of Urban RWH models
Storage Tank Pipe System

18. Advantages
• RWH provides a good supplement to other water sources
thus relieving pressure on other water sources.
• It can supply as a buffer and can be used in times of
emergency or breakdown of public water supply systems.
• Helps reduce the storm drainage load and flooding in the
cities.
• It is a flexible technology and can be built to require meets
of any range. Also the construction, operation and
maintenance is not very labour intensive in most systems.

19. Advantages
• Prevents water wastage by arresting run off as well as prevents soil
erosion and mitigates flood.
• Sustains and safeguards existing water table through recharge.
• Arrests sea-water intrusion and prevents salination of ground
water.
• Rainwater harvesting can reduce salt accumulation in the soil
which can be harmful to root growth. When rainwater percolates
into the soil, it forces the salts down and away from the root zone
area. This allows for greater root growth and water uptake, which
increases the drought tolerance of plants.
• Rain-water is a clean and pure source of drinking water which
requires minimal chemical treatment as the amount of pollutants
are not much.

20. Disadvantages
• In terms of complex constructions, there is a requirement for high
costs, trained professionals.
• Maintenance costs may add to the monetary burden.
• If not maintained properly then it can cause various problems in
terms of algal or bacterial growth.
• Tanks if not constructed properly might result in leakages and
metal tanks may also lead to problems such as corrosion harming
the water quality.
• All these factors might prove harmful and result in various kinds of
health issues.
• The system is very much rainfall dependent and hence if there are
problems with the rainfall in the area, it may not be very effective.

21. Future of Rainwater Harvesting
• Rainwater harvesting systems serve as an
alternative decentralized water source especially
in the age when groundwater supplies are
depleting and municipal water infrastructures
are facing high replacement costs.
• The use of decentralized rainwater harvesting
systems is growing nationally and
internationally, especially in industrial countries
like Asia, Europe and the US.

29. • Roof Rain Water Harvesting
• Land based Rain Water Harvesting
• Watershed based Rain Water harvesting
• For Urban & Industrial Environment –
• Roof & Land based RWH
• Public, Private, Office & Industrial buildings
• Pavements, Lawns, Gardens & other open spaces
RWH – Methodologies

30. RAIN WATER HARVESTING TECHNIQUES :
There are two main techniques of rain water
harvestings.
• Storage of rainwater on surface for future use.
• Recharge to ground water.
The storage of rain water on surface is a traditional
techniques and structures used were underground
tanks, ponds, check dams, weirs etc

31. Recharge to ground water is a new concept of
rain water harvesting and the structures
generally used are :-
Pits :- Recharge pits are constructed for
recharging the shallow aquifer. These are
constructed 1 to 2 m, wide and to 3 m. deep
which are back filled with boulders, gravels,
coarse sand.

32. • Trenches:- These are constructed when the
permeable stream is available at shallow
depth. Trench may be 0.5 to 1 m. wide, 1 to
1.5m. deep and 10 to 20 m. long
depending up availability of water. These
are back filled with filter materials.
• Dug wells:- Existing dug wells may be
utilised as recharge structure and water
should pass through filter media before
putting into dug well.

33. Appropriate Technology
Water conservation
and groundwater
recharge techniques
Water harvesting cum
supplementary
irrigation techniques

34. Hand pumps :- The existing hand pumps may be
used for recharging the shallow/deep aquifers,
if the availability of water is limited. Water
should pass through filter media before
diverting it into hand pumps.
Recharge wells :- Recharge wells of 100 to 300
mm. diameter are generally constructed for
recharging the deeper aquifers and water is
passed through filter media to avoid choking of
recharge wells.

35. Recharge Shafts :- For recharging the shallow
aquifer which are located below clayey surface,
recharge shafts of 0.5 to 3 m. diameter and 10 to
15 m. deep are constructed and back filled with
boulders, gravels & coarse sand.
Lateral shafts with bore wells :- For recharging the
upper as well as deeper aquifers lateral shafts of
1.5 to 2 m. wide & 10 to 30 m. long depending
upon availability of water with one or two bore
wells are constructed. The lateral shafts is back
filled with boulders, gravels & coarse sand.

36. Spreading techniques :- When
permeable strata starts from top
then this technique is used. Spread
the water in streams/Nalas by
making check dams, nala bunds,
cement plugs, gabion structures or a
percolation pond may be
constructed.

37. Rain Water Harvesting?.
Rain Water Harvesting RWH- process of collecting, conveying
& storing water from rainfall in an area – for beneficial use.
• Storage – in tanks, reservoirs, underground storage-
groundwater
• Hydrological Cycle

38. Harvesting System
Broadly rainwater can be harvested for two purposes
•Storing rainwater for ready use in containers above or
below ground
•Charged into the soil for withdrawal later (groundwater
recharging)
Source: A Water Harvesting Manual For Urban Areas

39. Rain Water Harvesting?
• RWH - yield copious amounts of water. For an average rainfall
of 1,000mm, approximately four million litres of rainwater can be
collected in a year in an acre of land (4,047 m2), post-
evaporation.
•As RWH - neither energy-intensive nor labour-intensive
•It can be a cost-effective alternative to other water-accruing
methods.
• With the water table falling rapidly, & concrete surfaces and
landfill dumps taking the place of water bodies, RWH is the most
reliable solution for augmenting groundwater level to attain self-
sufficiency

40. 16
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

41. 17
Rain water harvesting system
The typical roof top rain water harvesting system comprises
• Roof catchment
• Gutters
• Down pipe & first flushing pipe
• Filter Unit
• Storage Tank

42. 18
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

43. 19
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.

44. 20
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

45. 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

46. 22
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.

47. 23
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.

48. 24
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

49. 25
Water available from Roof
Annual rainfall (in mm) x roof area (in sq. m) x co-
efficient of run off for roof
co-efficient of run off
GI sheet 0.9
Asbestos 0.8
Tiled 0.75
Plaster on bricks/ Concrete 0.7

50. Watershed Management
• What is a watershed??
• Watersheds can be defined as a geo-hydrological
unit draining to a common point by a system of
drains. All lands on earth are part of one
watershed or other. Watershed is thus the land
and water area, which contributes runoff to a
common point.
• For example, the watershed of a lake would
include not only the streams entering that lake
but also the land area that drains into those
streams and eventually the lake.

51. Water Shed

52. Water shed

53. Water Shed

54. Watershed Management – Definition
• The process of creating and implementing plans,
programs, and projects to sustain and enhance
watershed functions that affect the plant, animal, and
human communities within a watershed boundary.
• Watershed management is the integrated use of land,
vegetation and water in a geographically discrete
drainage area for the benefit of its residents, with the
objective of protecting or conserving the hydrologic
services that the watershed provides and of reducing
or avoiding negative downstream or groundwater
impacts. Fresh water, and freshwater ecosystems, is the
most basic components of watershed management.

55. Need for Watershed Management.
• In spite of sufficient rainfall, people have to
depend upon tankers for their domestic water
supply in summers in most of the areas. This is
mainly due to large runoff which is responsible
for water loss as well as soil loss of the land.
• A raindrop, when flows along the slope, carries
the loose soil along it. In this case the topmost
layer of soil is lost rapidly. Due to high intensity
rainfall, it is estimated that, more than 100 tons
of soil is lost .

56. Objectives of Watershed management
• To control damaging runoff and degradation and thereby conservation
of soil and water.
• To manage and utilize the runoff water for useful purpose.
• To protect, conserve and improve the land of watershed for more
efficient and sustained production.
• To protect and enhance the water resource originating in the watershed.
• To check soil erosion and to reduce the effect of sediment yield on the
watershed.
• To rehabilitate the deteriorating lands.
• To moderate the floods peaks at downstream areas.
• To increase infiltration of rainwater.
• To improve and increase the production of timbers, fodder and wild life
resource.
• To enhance the ground water recharge, wherever applicable.

57. Watershed Development
• Watershed development refers to the
conservation, regeneration and the judicious
use of all the resources (Natural and Human)
Within a watershed.

58. Steps Involved in Watershed
Development
• Human Resource management
• Soil and land management
• Water management
• Crop management
• Afforestation
• Rural energy management
• Livestock management

59. Human Resource Management
• Training is essential to enhance the technical ,
social and managerial capacity of workers,
especially the NGO’s and VWC’s involved in
the watershed development
• The NGO staff, village watershed committee
and watershed committees have been
provided training through on field’ hands on’
structured and farmer to farmer extension

60. Soil and Land Management
• Soil Management: The soil Conservation
methods should be adopted in the catchment
area. The erosive power of natural agents
(Wind, Rain) and erodibility properties of the
soil combine to causes oil erosion
• The process gets accelerated with increase in
slope of the land surface and retarded by
decreasing in the slope

61. Soil Management
• The soil erosion can be decreased by
intercepting the erosive power of rain and
wind with vegetation cover, by increasing the
roughness of land surface by different tillage
operations by decreasing the slope of land by
adopting practices like bunds, terraces, and
other such structures.

62. Conserving Soil and Water
• Contour - Contour trenches trap rain water,
enable it to percolate to underground aquifers
and break the speed of fast moving water
• Gully control - Gully plugs help to control the
flow of water, sedimentation and recharge
ground water aquifers.
• Stone bunds - Building stone and nala bunds
across the slope arrest the flow of water and
control erosion in areas where soil work is not
possible.

63. Contour Bunds Stone Bunds

64. Check Dams Gully Control

65. Vegetation Cover

66. Bunds

67. Bunds

68. terraces

69. Land Management
• If the agriculture land is undulated the water is
lost by trapping, so the agricultural land should
be properly levelled to obtain uniform growth of
plants with optimum uniform quantity of water
• The deep ploughing by tractors is much efficient
to retain water and to get maximum yield with
optimum supply of water.
• Along the slops of hills area contours, bunds, or
terrace bunds should be constructed at different
levels which arrest the sediments and serve as
detention basin for heavy runoff season.

70. Deep Ploughing

71. Water Management
• Benefits may be obtained by utilizing
minimum volume of water, so the water
management is a science of proper
management of water by the cultivators
• •Methods of water management
• Reservoir management.
• Conveyance system management.
• Application of right amount of water

72. Reservoir Management
• The Reservoir management involves the
method of reducing evaporation losses (use of
chemicals like cethyl alcohol), absorption and
percolation losses (by making reservoir
Impervious by techniques like grouting)

73. Conveyance System Management
• The canals should be lined to reduce seepage
losses

74. Application of right amount of water
• The right amount of water should be applied to the
land which is just sufficient to meet the water
requirement of crop.
• Eg. Different crops require different quantity of water
to come to maturity
• The amount of water required by them is known as
delta i.e. ht of water measured in cm required by the
crop
• Sugarcane-120 cm
• Rice -120 cm
• Cotton 50 cm

75. Crop Management
• The crop management should be practices for
maintaining the fertility of the lands for
obtaining maximum yield with minimum supply
of water, correct method of irrigation
• •Border strip method-for wheat, vegetables
• •Furrow methods-for cotton, sugarcanes
• •Basin methods-For orchards
• •Sprinkler methods-for groundnuts, vegetables
• •Drip method-for all types of crops.

76. Furrow Irrigation

77. Basin Method

78. Sprinkler Method

79. Drip Method

80. Afforestation
• Planned growth of trees in wasted, restricted
area is a valued aspect of greening. These
conservation measures can reduce soil erosion

81. Rural Energy Management
• Prevention of local environment degradation
by replacing traditional fuel sources by
renewable energy sources.
• This reduces the agony of rural women
• It mitigates the indoor air pollution

82. Traditional methods of cooking food

83. Renewable energies
• Bio gas plant
• Solar cookers
• Solar panels

84. Livestock management
• The live stock population in the watershed
comprises of cows, bullocks, buffaloes, sheep,
goats, and camels, the live stock owner
normally provides water to large animals
either in the home or the animals are taken to
farmwells. Water availability situation, is also
found to be affecting livestock population. So
necessary steps should be taken to grow the
population of live stock provide them food
and shelter and health.

85. Live stocks
• Drinking water
• Health care for live stocks

86. Shelters

87. Water Shed community

88. Advantages/Future Of WSM
• Watershed Development program is a revolutionary
program aimed at fulfilling the water needs in the water
scarce areas.
• In areas where there is inadequate water supply watershed
management offers an ideal solution.
• It helps in utilizing the primary source of water and
prevents the runoff from going into sewer or storm drains,
thereby reducing the load on treatment plants.
• If we take steps to encourage each drop of rainfall to
penetrate in the ground at the point where it strikes earth,
it will result in addition of one drop to our useful water
supply and subtraction of one drop from a potential flood.

89. Water Shed Community

91. Thank You