Definition of drought, Causes of drought, measures for water conservation and augmentation, drought contingency planning. Water harvesting: rainwater collection, small dams, runoff enhancement, runoff collection, ponds, tanks.

1. MODULE- V
Drought Management and
Water Harvesting
Prepared by
Bibhabasu Mohanty
Dept. of Civil Engineering
SALITER, Ahmedabad

2. Contents
Definition of drought, Causes of drought,
measures for water conservation and
augmentation, drought contingency
planning.
Water harvesting: rainwater collection,
small dams, runoff enhancement, runoff
collection, ponds, tanks.

3. Introduction
Normal, recurrent feature of climate
Occurs everywhere, vary from region to region.
Originates from deficiency of precipitation.
Impact on ecosystem and agricultural of affected
region.
Drought leads to food insecurity, famine,
malnutrition, epidemics and displacement of
populations.

4. Types of drought
Meteorological drought
Agricultural drought
Hydrological drought
Socioeconomic drought

5. Causes of drought
Reduced rainfall results in drought.
Occurs because water vapour not brought by air
currents to right areas at right times.
Unusual currents of cold and warm water in
oceans creates high pressure. El Nino causes
drought in Asia.
Mountain prevent wind from blowing moisture
to needy region.

6. In India when water vapour moves from east to
west, water vapour does not leave Indian ocean
causes drought.
Human activity directly trigger over farming,
excessive irrigation, deforestation.
Global warming result in rainfall in some areas
and drought in some areas.

7. Drought contingency planning
To provide contingency plans to manage
drought and emergency conditions.
To continue to deliver a cost effective, adequate,
safe and reliable supply of water.
The provision of credit or cash/food for work
Maintaining water supply for animals and
humans

8. Maintaining cereal availability
Human and livestock health service provision
Support for private sector
Provide fodder for affected stock
Flexible taxation systems for affected people

9. Drought contingency planning allow for
implementation of :
Mitigation
Relief
Rehabilitation

10. Drought contingency planning for
implementation:
Overall drought policy, setting out plans
objectives of minimizing the impact of drought
Set plans for specific mitigation, relief and
rehabilitation measures
Construction of dams and additional reservoirs
for supply of water.
Cloud seeding- artificial rain

11. Desalination of sea water for irrigation or
consumption.
Drought monitoring by total rainfall levels and
total usage levels
Land use by carefully planned crop rotation
Outdoor water use restriction
Rainwater harvesting
Recycled water
Relief works
Disease prevention and control

12. • Contingency planning done by Govt.
 Policy issues, national, regional and district level
 rural development infrastructure
 input supply, marketing and farm advisory
services
• Non- Govt.
NGO’S
Rural institutions
Private sectors

13. Augmentation of water
It includes methods for providing an entirely
new supply of fresh water and techniques for
increasing utility of available supplies of water.
New supply of water include weather
modification.
Weather modification done to increase
precipitation and decrease Evapotranspiration.
Cloud seeding done to increase precipitation.

15. Available water supplies increased by conservation
of available water supplies.
Agricultural water requirements can be reduced
by reducing conveyance losses, and discouraging
wasteful irrigation techniques.
Technique should be developed to reduce water
consumption in home and industry.
Evaporation losses from small reservoirs can be
reduced by providing roofs.

16. Reclamation and reuse of waste water can be
encouraged.
Evaporation loss in ground water is less. Use of
ground water storage reservoir in conjunction
with surface storage reservoirs.
Infiltration losses can be reduced by sealing the
soil surface useful in arid regions.
Water harvesting done by collecting from roof
top, pavements, constructing small storage.

17. Measures for water conservation
Goals of water conservation efforts include:
Sustainability- ensure availability for future
generations
Energy conservation- world 15% energy
production dependent on water management.
Habitat conservation- preserve fresh water
habitat, migrating waterfowl.

18. Benefits of water conservation:
Save water save money.
Reduction in excess water use reduce waste
water generation, reduce overflowing of gutter.
Ecosystem and habitat protection.
Helps in improving quality of drinking water.

19. Water conservation measures by:
Domestic conservation
Industrial conservation
Agricultural conservation

20. Domestic conservation
Repair all leaks quickly
Turn off water when not in use
Use conserving appliance which use low volume
water for domestic use
Local bodies should install water meter and
encourage water pricing.

21. Industrial conservation
Use cooling system which use less water.
Reuse of cooling water for irrigation or other
purposes.
Install in plant treatment measures for treating
the waste water or effluent.

22. Agricultural (irrigation) conservation
Improved irrigation methods such as sprinklers
or drip irrigation.
Water required for agricultural considerably
reduced by reducing conveyance loss.
Evaporation losses from small reservoirs can be
reduced by providing roofs over them.
Use of lined canals which reduce seepage and
evaporation.

23. Use of ground water storage reservoir in
conjunction with modern surface storage
reservoirs to reduce evaporation loss, in arid
regions.
Price agricultural water to encourage
conservation.
Infiltration losses reduced by sealing soil surface.
Water harvesting in arid regions.

24. For conservation of water the following
structures can be constructed:
Earthen bund
Gully plugging
Check dam
Khet talawadi

25. Earthen bund

26. Gully plugging

27. Check dam

28. Khet Talawadi

29. Water harvesting
Collection of rain water called water harvesting.
Rainwater harvesting is accumulation and
storing of rainwater for reuse, before it reaches
aquifer.
Water collected from roofs of houses, schools,
local institutions make important contribution.
Water collected from ground, called storm water
harvesting.

30. Benefits of rainwater harvesting
Increase water availability
Checks declining water table
Environmental friendly
Improves water quality of ground water
Surface water runoff conservation
Prevents soil erosion and flooding in urban area

31. Rainwater harvesting technique
Rainwater collection – Roof top rainwater
harvesting
Runoff collection – Surface runoff harvesting
Recharge to ground water
Runoff enhancement

32. Roof top rain water harvesting
Rainwater captured from roof catchments and
stored in sub surface ground water reservoir.
Objective is to make water available for future
use.
Useful in dry land, hilly, urban and costal areas.

33. Components of roof top rainwater harvesting
 a collection area
 a conveyance system
 storage facility
 a delivery system
Storage reservoir expensive part, careful design
and construction required.
First rainwater should be flushed or diverted.

36. Surface runoff harvesting
Surface runoff harvesting is traditional
technique.
Small dams, ponds, tanks are used.
Used for irrigation, domestic, livestock use.

37. Small dams
Small dams/check dams constructed in natural
channel to impound the runoff water up to
certain depth.
Impounded water slowly infiltrate into soil and
recharge ground water.

38. Ponds and reservoirs
Impounding type and dug-cut type ponds
constructed.
In impounding type, a retaining wall or dam is
constructed to block the flow of water in a
natural storm.
In dug-cut type area is excavated to store the
runoff.
Reservoirs requires water storage area, spillways
and earth embankment.

39. Storage tank
Surface or above ground tank
Subsurface or underground tank
Storage tanks require
Solid secure cover
Coarse inlet filter
Overflow pipe
Manhole, sump and drain to facilitate cleaning
Outlet system, tap or pump

40. Recharge to ground water
The structures generally used:
Pits
Trenches
Dug well
Hand pumps
Recharge well
Spreading techniques
Underground reservoirs

41. Runoff enhancement
Can be done by increase precipitation.
Seeding generally done to increase precipitation.
Precipitation can be increased by 10% by cloud
seeding.
Lumb demonstrated that increase in annual
runoff (∆R) due to small increase in precipitation
(∆P) is given by
∆R= ∆P (0.29+1.2 R/P)
R= mean runoff, P= mean precipitation

42. Methods for runoff enhancement:
Cloud seeding
Enhancement by paved surfaces.
Surface of drainage basin effect on runoff. Bare
surface give more runoff.
Drainage basin located on windward side of
mountain produce more runoff.
Runoff affected by geology of drainage basin.
Pervious soil yield less runoff.

43. Drainage basin has larger no of natural
depressions, which deposited by other material
then runoff at basin increases.
More Human activity, more load on soil, reduce
infiltration, hence increase runoff.

44. ASSIGNMENT

45. 1. Discuss various causes of drought
2. Discuss drought contingency planning and its
importance.
3. Explain augmentation of water and its various
methods.
4. Explain water conservation and its various
methods.
5. Discuss importance of rainwater harvesting and
explain various techniques used for it.