Drought is characterized by a deficit in moisture supply over a period of time, resulting in less than normal availability of water. It can be classified as meteorological, hydrological, or agricultural drought depending on whether it is defined based on rainfall, streamflow and reservoir levels, or soil moisture and crop impacts. Some consequences of drought include reduced agricultural production, impacts on hydropower generation and regional economies, and reduced water quality. Drought management strategies include early warning systems, monitoring, assessment, proper soil and water conservation practices, irrigation scheduling, cropping pattern changes, inter-basin water transfers, groundwater development, and water harvesting techniques.

1. RUNOFF
Prepared by:
SUZILAWATIE BT ABDUL GHANI
P 60832

2. Drought
Surface Water Resources of India

3. A climatic anomaly characterized by deficit
Definition supply of moisture
Result from Causing
• Subnormal rainfall over large • Below normal natural
region availability of water over
long periods of time
Characteristic Develop in a region over a
Meteorological drought
length of time
Classification
Agricultural production Hydrological drought
Hydropower generation
Consequence
Regional economy
Quality of available water Agricultural drought
Highly degraded Environmental Health

4. Meteorological Drought
Classification
It is a situation where there
is more than 25 % decrease
in precipitation from
normal over an area Moderate : seasonal Severe : seasonal
 actual rainfall less than deficiency between deficiency above
climatological mean of that 26% and 50% 50%
area
Drought year :
affected by Drought prone area :
moderate or severe drought occur in an
more than 20% of the area with probability
total area of the 0.2 < P < 0.4
country

5. Hydrological Drought
Drought mean below
average values of End of drought : adequate rainfall saturates the
stream flow, contents soil mass and restores the stream flow and
in tanks and reservoir contents to normal values is relatively
reservoir, groundwater easy to determine
and soil moisture
Importants of hydrological studies:
C Design and operation of reservoir
Magnitude
O Diversion of stream flow for :-
M Irrigation
P Duration Power
O Drinking water
N Severity
E
N
T Frequency of occurance

6. Agricultural Drought
An indicator of possible moisture
Aridity Index
stress experinced by crop
Inadequate soil moisture (AI) AI = ( PET – AET ) x 100 PET = potential evaporation
resulting in acute crop
PET AET = actual evaporation
stress and fall in Aridity is the
Normal value = AI anormaly
agricultural productivity Thornthwaites’s
(moisture shortage)
Principal criteria : concept to
describe water AI anomaly Severity Class
deficiency of rainfall
deficiency Zero or negative Non-arid
experienced by 1 - 25 Mild arid
plant 26 - 50 Moderate arid
> 50 Severe arid
Produce AI anomaly maps of
INDIA on bi-weekly basis based Palmer Index
on data from 210 station (PI)
Used to characterize agricultural
IMD
Moisture drought
Represent different agro-
Availability
climate zone in the country Index (MAI)

9. Drought Management
Temporal and spatial aberrations in
the rainfall
CAUSE
Improper management of available
water
Lack of soil and water conversation
Short-term Long-term
strategies strategies
Drought
mitigating
Early measures
warning Proper soil
Monitoring and water
Assessment conservation
Irrigation
of the drought scheduling
Cropping
pattern

10. Cloud Seeding
Cloud seeding is the process of
spreading chemical into the upper part
of clouds to try to stimulate the
precipitation process and form rain
The most common chemicals used for
cloud seeding include silver iodide and
dry ice (solid carbon dioxide)
Cloud seeding chemicals may be
dispersed by aircraft or etc. For release
by aircraft, silver iodide flares are
ignited and dispersed as an aircraft flies
through the inflow of a cloud
The formation of ice particles in
supercooled clouds allows those particles
to grow at the expense of liquid droplets.
If sufficient growth takes place, the
particles become heavy enough to fall as
precipitation from clouds

11. Drought Management
Creation of water storage through appropriate water resource
development
POSSIBLE
MEASURE Inter-basin transfer of surface water from surplus water areas to
drought prone areas
FOR
MAKING
DROUGHT
PRONE Development and management of ground water potential
AREAS LESS
VULNERABLE
TO
DROUGHT Development of appropriate water harvesting practices
ASSOCIATES
PROBLEM
Economic use of water in irrigation through practices such as drip
irrigation and sprinkler irrigation

12. Water Harvesting
DEFINITION (FOA)
The process of collecting and
concentrating runoff water
from a runoff area into a run-
on area, where the collected
water is either directly
applied to the cropping area
and stored in soil profile for
immediate use by the crop
(runoff farming or stored in
an on-farm water reservoir)
for future productive uses
(domestic use, livestock
watering, aquaculture and
irrigation)

13. Roof Top Water Harvesting (RTWH)
Definition  The productive utilization of rain water falling in roof-tops of structures
 Urban area :- roof tops are impervious and occupy considerable land area
Factor  Water supply :- inadequate , inefficient , unreliable
Advantage  Economic
Micro Catchment System (Within The Field) of Rainwater
 System :- the catchment is small area - not put for any productive purpose
 Length :- between 1 – 30 metres
 During storm :- overland flow is harvested by collecting and delivering it to
Characteristic a small cultivated area
 Ratio :- catchment to cultivated area = 1:1 to 3:1
 Overflow :- no provision

14. Micro Catchment System (Within The Field) of Rainwater
Negarim Micro Catchment
Dividing the catchment into a
large number of micro
catchment in a diamond
pattern along the slope
Each micro catchment is of
square shape with a small
earthen bunds at its boundary
and an infiltration pit is
provided at the lowest corner
The pit is the cultivated area
and usually a tree is grown in
the pit
The arrangement of micro
catchment of sizes 10m^2 to
100m^2

15. Macro Catchment System (Within The Field) of Rainwater
The system is designed for slightly larger catchment area where overland
Definition flow and rill flow is collected behind the bund allow to be stored in the soil
profile through infiltration
 Length :- 30 to 200 m long
 Ratio :- catchment to cultivated area = 2:1 to 10:1
 Arrangement :- one row or two staggered rows of trapezoidal bunds with
Characteristic wing wall
- contour bunds made a piled up stones
 Overflow :- for disposing of the excess runoff water
 Infiltration area :- use to grow crop

16. Floodwater Farming ( Floodwater Harvesting )
 Length :- several kilometres long
Characteristic
 Ratio :- catchment to cultivated area = larger than 10:1
Small structures are built across the drainage to Check Dam Nalabund
store part of the runoff
Store water : utilisable for community
Storage Structure System
Infiltration : recharge to the ground water
Advantages :- arresting erosion from the
catchment
- prevent the deep and widen of gullies
Check Dams :- masonry overflow spillway Cement Nalabund
- flanks : masonry / earthen embankment
- lower stream (up to 3) with median slope
Nalabunds :- across streams for impounding
runoff flow to cause a small storage
- objective ~ improve water percolation
~ improve of soil moisture regime
- material ~ earthen embankment
- spillway ~ stone lined/rock cut steep channel
- construct ~ flat reach of a stream with
slopes less than 2 % Earthen Nalabund

17. Water Spreading
Diversion across the drainage would cause the runoff to flow on the
Spreading of Water
adjacent land. The water is forced to leave its natural course and
conveyed to nearby cropping fields
Appropriates bund cause spreading the water over the command
Spread water infiltrates into the soil and is retained as soil moisture
Provision for overflow spillway at the diversion structure, to pass
excess water onto the downstream side of the diversion
structure, IMPORTANT component of diversion structure
Drought in INDIA
Faced 29 1918 Affect
drought year – the worst –agriculture
since year production
1875 -2004 (70% effected) - economy

18. Surface Water Resource
In most of the basin of the country, the surface
water resource have been develop
Utilize through diversion structure and
reservoir
Utilization produce return flow
Definiton : non-comsumptive part of any
diversion returned back
Total Catchment Area (all river)
= 3.05 mil km
Large : larger than 20,000 km^2
Medium : between 20,000 to 2,000 km^2
Small : less 2,000 km^2

19. Utilizable Water Resource
Definition  the quantum of water withdrawable from its place of natural occurrence
 topographic conditions
Depend
 availability of land
 Not be possible to utilize entire surface water resource because:-
- topography
- environmental consideration
Limitation - non-availability of suitable location
- technology shortcoming
- evaporation
- percolation

20. Utilizable Water
Resource
CWC in 1988
Utilizable surface water
resource = 690.32 km^3

21. Utilizable Dynamic Groundwater Resource
Estimate by  CGWB
 Total replenish-able water groundwater resources is 431.89 km^3/year
 Utilizable dynamic groundwater potential is 396 km^3/year
Water Available from Return Flow
Water Resource
Surface flow
Consumptive Due to
economic, technology
returned backs
constraints and diminished
Groundwater system water quality  part of
Non-Consumptive
return flow is recoverable
for re-use
Soil moisture

22. Total Water Requirement
Estimated by NCIWRD
Highest  Irrigation (68%)
Evaporation
Evaporation losses
NCIWRD adopted
- 15% of the live storage
capacity of major project
- 25% of the live storage
capacity of minor project

23. Demand and Available
Water Resources
The summary of NCIWRD
study relating to
national level
assessment of demand
and available water
resource
The return flow
contributes 20-25% in
reducing the demand

24. THANK YOU