Drought & Desertification measures of mitigation ,Types of drought ,Drought Causes, Effects of Drought . Types of deserts and the global distribution of deserts, Factors for desert formation, Mitigation:

1. Drought
&
Desertification
measures of mitigation
S.K. PATRE

2.  Water is an essential resource for survival
of life, however excess of it can cause
calamity and lack of it can cause disaster.
Excess of water than required can cause
flood and on the other hand water deficit
can cause drought. Flood and drought are
extreme negative situations caused due to
water imbalances.

3. DROUGHT
 Drought is also an extreme situation, which happens due
to insufficiency of precipitation over a longer period causing
damages to crops. Definition of drought varies in different
countries and regions depending on the average
precipitation level of the country such as countries or
regions.
 According to India Meteorological Department (I.M.D.), the
drought in India is a situation occurring in any area when
the mean rainfall of a year is less than 75% of the mean
annual rainfall. I.M.D. classified drought in two broad
categories:-
i. Severe Drought: When the deficiency of rainfall exceeds
50% of the normal rainfall.
ii. Moderate Drought: When the deficiency of rainfall is
between 25% and 50% of the normal rainfall.

4. TYPES OF DROUGHT
 Types of drought are classified in various ways,
taking different parameters related to physical
and climatic characteristic of an area. The
principal characteristic is rainfall as drought is
directly related to water scarcity.
 Here types of drought are classified in three
different groups:
1. Drought due to scarce rainfall.
2. Drought depending on the universal
hydrological cycle.
3. Drought on the basis of spatio-temporal
pattern of rainfall.

5. Drought due to scarce rainfall

6. Drought Depending On The Universal Hydrological Cycle:
 Climatic classification of Thornwaite,1948,Cf75 is based on
the rational approach on water balance which itself has
been developed from the universal hydrologic cycle.
According to Thornthwaite there are five major groups of
climate, namely.
• Perhumid (A),
• Humid (B),
• Sub humid (C) - Moist sub-humid (C1)
Dry sub-humid (C2),
• Semi Arid (D),
• Arid (E)
 The perhumid and the humid climatic groups belong to the
humid category, while the two dry climates, the semi arid
and the arid, have drought proneness or can be said as
regions having permanent feature of drought.

7. Drought On The Basis Of Spatio-Temporal Pattern Of
Rainfall:

8. Drought Causes
If flood happens due to excess of water than
drought due to lack of it and dryness and
resultant lack of agricultural production leads to
drought situation. The major causes of drought
are:
 Lack of precipitation: When the level of
precipitation is less than about 75% of the
normal average, over a long period of time,
drought happens. The drought condition is more
prevalent when agricultural production gets
impacted due to lack of rainfall and irrigation
facilities.

9.  Reduction of surface water flow: When the flow of surface
water bodies like streams and rivers reduces or the rivers get
dried up due to storage of water in dams/ reservoirs in the
upstream for hydro power plants and irrigation facilities, drought
like situation happen in the downstream regions of the river.
 Deforestation: Hydrological cycle (including evaporation,
precipitation and condensation) of the earth is maintained by
plants and trees. Trees have water retention capabilities, can
control evaporation and maintain ground water level.
Deforestation due to excessive population growth and various
economic activities has exposed the surface to erosion and
reduced the level of ground water and the ability of the earth
surface to hold water, as a result with prolong period of dryness,
desertification and drought crises appears.
 Global Warming: Rise in global temperature due to increase in
greenhouse gases has impacted the climate drastically as a result
many areas goes dry and forest catches fires leading to
desertification and drought like condition.

11. Effects of Drought
Environmental Impacts of
Droughts
Animal and plants die off as a
consequence of drought. Mainly, the
damages arise out of extensive
destruction of the wildlife habitats
and reduction in water quality and
quantity. Some plants and animals
may completely fail to recover after
the drought. The overall climate, the
rocks, and soils are also affected,
negatively impacting various living
and non-living factors.

13.  Drying out of water bodies.
 Reduction in soil quality.
 Unsuitable conditions for plant
and vegetation survival.
 Migration and even death of
Animals and Wildlife.

14. Economic Impacts of Droughts
 Reduced crop yields.
 Industrial and governmental losses.
 Outbreak of waterborne diseases.
 Hunger, anemia, malnutrition, and
deaths.
 Migration of people and anxiety.

15. Range Of Possible Social Consequences Of Drought

16. Deserts and Desertification
 Deserts: They are subtropical arid regions
where potential evaporation is approximately
>2000mm and the annual precipitation is about
<200mm.
 Desertification: It is the process where land
is degraded and becomes relatively dry, arid and
loses water bodies, vegetation and wildlife. It can
be caused due to climate change and through
human induced activities. The United Nations
Convention to Combat Desertification (UNCCD)
has defined desertification as “land degradation
in arid, semi-arid and dry sub-humid regions
resulting from various factors, including climatic
variations and human activities.”

17. Types of deserts and the global distribution of deserts
(a) Hot deserts: These are situated near the equator. The temperatures
during day time can be more than 38ºC and the nights are very cold.
Examples of hot deserts are the Great Sandy Desert and the Simpson
Desert in Australia.
(b) Cold deserts: They are found away from the equator in the centre of
continents. They are characterized by high mountainous areas. As the
name indicates, these deserts are covered by snow and ice during winters.
Examples of cold deserts are the Patagonian Desert in Argentina and
Antarctica.
(c) Inland deserts: These deserts are found far away from the sea. They
form in the centre of large continents where they are protected from the
blowing winds. When clouds over the oceans rise over mountains rainfall
occurs. Then the air left is dry. When this air moves inland no rainfall
occurs. This is the reason deserts in the centre of Kalahari and Australia
are dry.
(d) Coastal deserts by the sea: They are found on the west coast of the
earth’s continents. These deserts have warm summers and cool winters.
Hence they are referred to as cool deserts. Some examples are the Namib
Desert in south-western Africa and the Atacama Desert in South America.

18. (e) Semiarid deserts: These deserts receive 250 to 350mm of
rainfall. The summers have temperatures of 20°C and
30°C and are long and dry periods. More than one-third of
Australia is a semiarid desert.
(f) a) Subtropical Deserts: These are located at latitudes
near or above the Tropic of Cancer and Tropic of
Capricorn: These include the following.
Tropic of Cancer: The deserts include the great Sahara
desert of North Africa and the Arabian desert of the Middle
East.
Tropic of Capricorn: The deserts include the deserts in the
Australian interior, and the deserts in the interior Pampas
of Argentina.
g) Mid-latitude Deserts: These deserts include the Gobi
desert of central Asia and the deserts in the western
interior of the United States.

19. Factors for desert formation
The planet’s air circulation patterns and wind patterns are important factors for desert
formations.
a) Earth’s air circulation patterns: Most of the deserts are located between 15 to 30°
north and south of the equator. Here the trade winds blow offshore. The warm air holds
more moisture than cold air. Warm air rises at the equator and then cools. This cool air
has less water holding ability so precipitation is common at the equator. The dry air
mass moves north N30° and south S30°. At ±30° dry air sinks and warms. This
warm air can hold more water resulting in evaporation of water and desert formations.
Hence the equatorial region is tropical and ± ±30° is desert. An example is Sahara
desert.
b) Rain shadow effect: When hot rising air approaches a mountain it cools. This cool air that
crosses over the mountains is dry. Hence deserts are formed on the other side of the
mountain range. There is little precipitation on the leeward side also called as Rain
Shadow area desert. An example is the Gobi desert.
c) Distance from the ocean: This is also an important factor for desert formation. When
land is far away from oceans then deserts form. Near cold ocean currents: The
cold ocean air warms as it passes over continents. The warmer air holds
more moisture and causes evaporation and the formation of deserts.

20. Anthropogenic factors leading to desertification
Human beings can induce or accelerate the desertification process in many
ways. Overgrazing, deforestation, poor irrigation techniques etc. can
lead to desertification.
a. Overgrazing: This is unsustainable grazing. It occurs when
the number of cattle, goat that can graze an area exceeds the
carrying capacity of the land. When this capacity is exceeded
changes in vegetation occur. For example, drought-resistant
species replace edible species. Also the soil quality is reduced.
The animals break down the soil structure thus increasing its
vulnerability to erosion.
b. Over cultivation: This occurs when more food production
is required to feed large populations. over-cultivation is a
significant cause of desertification for it reduces soil fertility and
reinforces a cyclic decline in crop yield Even areas that are
considered suitable for cultivation may become degraded if they
are managed in a way that is inappropriate to the ecological and
climatic setting. Over-cultivation for agriculture as well as for
firewood contribute to soil degradation.

22. c. Deforestation: This occurs when
forest are cleared for agricultural purposes and
also for fuel wood. It leads to desiccation of the
soil and lowered water tables.
d. Inappropriate irrigation practices:
Poor irrigation techniques can result in reduced
soil fertility. This is due to salinisation and water
logging.

24. Mitigation:
 Desertification is an important aspect in eco restoration
programmes intended for implementation in deforested or
degraded or desert areas. Its mitigation in areas where the
process of desertification is progressing well is inevitable in order
to restore the area for sustainable development. A balance in
productive land and desert is required to keep the environment
and ecology sustainable.
 Stopping deforestation and starting afforestation are the
immediate steps towards rehabilitating the areas experiencing
desertification. Preventive measures are essential for halting the
spread of desertification process to other areas. These measures
require environmental education on desertification for local
communities and their participation in the restoration of the
degraded areas.
 It is usually not possible to return a decertified area to its pre-
decertified state but restorative measures are capable to
converting the degraded ecosystem into a new state that can
withstand cultural and land use pressures. Specific measures
include developing a resilient vegetation cover of mixed trees,
shrubs, scrubs and grass suitable for local conditions and
protecting soil against un favourable conditions.

25.  better and sustainable natural resource uses;
 optimization of existing resource uses and resource
sharing;
 education of and participation by the public in order to
improve the environment (water awareness);
 demand management and suitable development of water
resources and supply;
 conservation of all main ecosystems (including the aquatic
environment);
 maintenance of renewable resources (i.e. water resources
and systems);
 cost-effective restoration of degraded renewable resources;
 prevention of groundwater mining (i.e. when extraction is
higher than the recharge resulting in depletion of available
groundwater storage);
 reduction of evaporation losses from storage dams and
soils;prevention and control of water pollution;
 development of integrated catchment management and
conservation strategies in consultation with neighbouring
countries.

26. Strategy to handle the
drought condition requires following steps:
 Identification of drought prone areas in the country.
 Proper research work to study the pattern of rainfall for forecasting its
onset sufficient early, so that necessary steps can be taken earlier.
 Study the other physical and human resources of the area to determine
other problems and its effect on the process of development.
 To develop an integrated development strategy where efforts should be
more in the direction of creating permanent assets which would help to
solve the agrarian problems of these chronic scarcity affected areas for a
long period.
 Exercises in identification and development of drought prone areas are
meaning less without proper follow-up action. Thus, evaluation of
development work is needed for rectification of side effects of any
development project.

27. THANKS