This document provides information about various groundwater harvesting techniques. It discusses subsurface dykes/groundwater dams which create barriers underground to control groundwater flow and raise water tables. It also describes groundwater shafts, which efficiently recharge unconfined aquifers overlain by poorly permeable strata. Additionally, it outlines various rainwater harvesting measures like surface runoff harvesting and roof top rainwater harvesting systems along with their components and recharge methods. Finally, it mentions stream flooding as a low-cost surface water spreading method.

1. WELCOME
WELCOME

2. LWM 608 GROUND WATER ENGINEERING (2+1)
NAMITHA M R
ID. No: 2015664502
M.Tech. (Land & water management engg.)
AEC & RI, KUMULUR
Tamil Nadu Agricultural University
GROUNDWATER HARVESTING

3. Ground water dykes
(Sub-surface dykes)
Subsurface dyke is a barrier impermeable to
water, placed underground to control the
groundwater flow in an aquifer, and to
raise the water table
Also known as ground water dams

4. SUB-SURFACE DYKES

5. Contd…
Main purpose - Arrest the natural flow of
ground water and increase the storage
within the aquifer
Water levels in upstream of ground water
dam rises and saturate the otherwise dry
part of aquifer

6. Main advantages of groundwater dykes
Submergence of land can be avoided
Land above reservoir can be utilized
No evaporation loss from the reservoir takes
place
No siltation in the reservoir takes place
Collapse of dams can be avoided.

7. GROUND WATER SHAFTS
 Most efficient and cost effective technique to
recharge unconfined aquifer overlain by poorly
permeable strata
 Surplus water can be recharged to ground water.
 Diameter: 0.8 m (drilling) to 2m (manually
excavated)

8. GROUND WATER SHAFTS

9.  Shallow shafts: backfilled by inverted filter
boulders, gravel and sand
 Deeper shafts: lined, not necessarily
completely backfilled
 Shafts ends in more pervious strata below
confining layer, without touching water
table

10.  www.youtube.com/watch?v=c8BAXP5
aibI

11. WATER HARVESTING MEASURES
Conscious collection and storage of
rainwater to cater to demands of water, for
drinking, domestic purpose & irrigation is
termed as Rainwater Harvesting

12. Why harvest rainwater ?
 To arrest ground water decline and augment
ground water table
 To beneficiate water quality in aquifers
 To conserve surface water runoff during
monsoon
 To reduce soil erosion
 To inculcate a culture of water conservation

13. How to harvest rainwater?
Broadly there are two ways of
harvesting rainwater:
(i ) Surface runoff harvesting
(ii) Roof top rainwater harvesting

14. Surface runoff harvesting:
In urban area, rainwater flows away as
surface runoff
This runoff could be caught and used for
recharging aquifers by adopting
appropriate methods.

15. Roof top rainwater harvesting:
System of catching rainwater where it
falls
Rainwater is collected from the roof of
the house/building
It can either be stored in a tank or
diverted to artificial recharge system

16. contd…
Less expensive and very effective
Helps in augmenting the ground water
level of the area.

17. Components of the roof top rainwater
harvesting system
 Roof catchment
 Drain pipes
 Gutters
 Down pipe
 First flush pipe.
 Filter unit
 Storage tank.
 Collection sump.
 Pump unit

18. Roof catchment
Catchment for collecting the rainwater
Style, construction and material of the roof
determine its suitability as a catchment
Roofs made of corrugated iron sheet,
asbestos sheet, tiles or concrete can be
utilized as such
Thatched roofs are not suitable

19. Drain pipes
 Pipes of suitable size, made of PVC /
Stoneware
To drain off the roof top water to the
storm drains

20. Gutters
Channels fixed to the edges of roof all around
to collect and transport the rainwater from
the roof to the storage tank
Shape: Rectangular or semi-circular
 Made of either plain Galvanized Iron sheets or
cut PVC pipes or split Bamboo

21. Rectangular gutters
Semi-circular gutters

22. Down pipe
Pipes that carries the rainwater from the
gutters to the storage tank
Down pipe is joined with the gutters at one
end, whereas the other end is connected to
the filter unit of the storage tank
PVC or GI pipes of 50mm to 75 mm (2 inch
to 3 inch) diameter are used

23. Most Common
Arrangement of
Down Pipe
Down Pipe

24. First flush pipe
Debris, dirt and dust collect on the roofs
during non-rainy periods
A first flush system can be incorporated in
the roof top rainwater harvesting systems
to dispose off the ‘first flush’ water so that
is does not enter the tank

25. Contd…
A separate vertical pipe is fixed to the down
pipe with a valve provided below the ‘T’
junction
After the first rain is washed out through
first flush pipe, the valve is closed to allow
the water to enter the down pipe and reach
the storage tank.

26. First flush pipe

27. Filter unit
 Filtration forms the most important
process in the purification of water
It involves allowing water to pass
through a filter media e.g. sand.
Filtration involves removal of suspended
and colloidal impurities present in water

28. Depending on the type of filtration, the
chemical characteristics of water may be
altered and the bacterial content may be
considerably reduced

29. Storage tank
Used to store the water that is collected
from the Roof tops
Small-scale water storage: Plastic
bowls, buckets, jerry cans, clay of
ceramic jars, cement jars, old oil drums
etc.

30. Large scale water storage: Bigger tank with
sufficient strength and durability
Construction materials: RCC, masonry,
Ferro-cement, PVC

31. Collection sump
Small pit is normally dug in the ground
beneath the tap of the storage tank for
collecting water form the storage tank
Constructed in brick masonry
Size of collection pit shall be 60 cm x 60
cm x 60 cm

32. Pump unit
Hand pump or a power pump fitted to the
storage sump facilitates lifting of water to
the user
Size of the pump has to be decided
depending upon the consumption of
the stored water.

33. TYPICAL ROOF TOP HARVESTING SYSTEM

34. Methods of Roof Top Rainwater
Harvesting
Storage of Direct use
Recharging ground water aquifers

35. Storage of Direct use
Rain water collected from the roof of the
building is diverted to a storage tank
Water from storage tank can be used for
secondary purposes such as washing and
gardening etc
Most cost effective way of rainwater
harvesting

36. Recharging ground water aquifers
 Commonly used recharging methods are:-
a) Recharging of bore wells
b) Recharging of dug wells.
c) Recharge pits
d) Recharge Trenches
e) Soak ways or Recharge Shafts
f) Percolation Tanks

37. a) Recharging of bore wells
 Rainwater collected from rooftop is diverted through
drainpipes to settlement or filtration tank
 Filtered water is diverted to bore wells to recharge
deep aquifers
 Optimum capacity of settlement tank/filtration tank
is designed on the basis of area of catchment,
intensity of rainfall and recharge rate

39. b) Recharging of dug wells.
Dug well can be used as recharge structure
Rainwater from the rooftop is diverted to dug
wells after passing it through filtration bed
Cleaning and desalting of dug well should be
done regularly to enhance the recharge rate

41. c) Recharge pits
Recharge pits- Small pits of any shape
constructed with brick or stone masonry wall
with weep hole at regular intervals
Covered with perforated covers
Bottom of pit should be filled with filter media.

42. contd…
Capacity of the pit can be designed on the
basis of catchment area, rainfall intensity and
recharge rate of soil
Dimensions of the pit: 1 to 2 m width and 2
to 3 m deep depending on the depth of
pervious strata

43. Suitable for recharging of shallow
aquifers, and small houses

44. d) Recharge Trenches
Provided where upper impervious layer
of soil is shallow
Trench excavated on the ground and
refilled with porous media like pebbles
 Size: 0.50 to 1.0 m wide and 1.0 to 1.5 m deep.

45. contd…
Usually made for harvesting the surface
runoff
Length of the trench is decided as per the
amount of runoff expected
Suitable for small houses, playgrounds,
parks and roadside drains.

47. e) Soak ways or Recharge Shafts
Provided where upper layer of soil is alluvial
or less pervious
Bored hole of 30 cm dia. up to 10 to 15m
deep, depending on depth of pervious layer
Bore should be lined with slotted/perforated
PVC/MS pipe to prevent collapse of the
vertical sides

48. f) Percolation Tanks
Artificially created surface water bodies,
submerging a land area with adequate
permeability to facilitate sufficient
percolation to recharge the ground water

49. Built in big campuses where land is
available and topography is suitable
Surface run-off and roof top water can be
diverted to this tank
Water accumulating in the tank percolates
in the solid to augment the ground water

50. Precautionary measures for harvesting
rain water
Roof or terraces uses for harvesting should
be clean, free from dust, algal plants etc.
Roof should not be painted since most
paints contain toxic substances and may
peel off
Do not store chemicals, rusting iron,
manure or detergent on the roof

51. contd…
Nesting of birds on the roof should be
prevented
Terraces should not be used for toilets either
by human beings or by pets
Provide gratings at mouth of each drainpipe
on terraces to trap leaves debris and floating
materials

52. contd…
Provision of first rain separator should be
made to flush off first rains
Do not use polluted water to recharge
ground water
Ground water should only be recharged by
rainwater.

53. contd…
Before recharging, suitable arrangements
of filtering should be provided
Filter media should be cleaned before
every monsoon season
During rainy season, the whole system
should be checked before and after each
rain

54. contd…
At the end of the dry season and just
before the first shower of rain is
anticipated, the storage tank should be
scrubbed and flushed off all sediments
and debris

55. STREAM FLOODING
Least costly surface water spreading
methods
Surface spreading method: Infiltration of
water from the surface of the soil
through the vadoze zone to the
saturated part of the aquifer

56. Surplus water from the canal or stream is
diverted to the adjoining areas through a
delivery canal
Embankments are made on two sides of
the area to ensure proper contact time and
water spread

57. Just remember…
THANK YOU….!!!!