Degree- Environmental Science and Outdoor Education at University of Stirling, Scotland 3rd Year (ENV U 6EH - Environmental Hazards.) Mind Map on Drought and desertification., created by meghansarah on 13/04/2015.
caused by unusual dry weather, which can be caused
by shifts in global weather patterns and increased by
human climate change. there is no guaranteed end
point to a drought.
Desertification
Impacs
Aridity
Aggravate health
conditions such a
asthma.
difference between different zones and
why something's can grow and others
cannot
Drought
Desertification
Drought
Seen thought history
4,200 years aga, lasted for centuries
was the world mega drought, caused
by the cooling of the Atlantic and
decreased rainfall by 30% and linked
to the fall of civilisations. (Heffernan 2013)
Global drought info service states
that there is a drought currently in
the planes of the USA
several different types:
Hefferman 2013
Meterlogical
Occurs when a persisitant
declines at the first stage of
te hydrological cycle, which
reduces the water which is
stored in ice/snow
it dosent rain as often
Soil moisture
affected by the hydrological and meteorological drought
Soil has dried out
and the water table
has dropped;
potential high evapotraspiration
Hydrological drought
caused by meteorological and affects soil moisture.
when the
water is not
available or
has
depleted
below a
level.
seen in the
lake/lochs/resivoirs
Aridity
How dry a place
Depends on several factors
Agroclimatic Zones
The agro-climatic classification is nothing but an extension of the
climate classification keeping in view the suitability to agriculture.
The most widely used classifications being Koeppen’s and
Thronghwaite’s. Generally, the climate types may be distinguished
on the rainfall, temperature and as these two characteristics are
influenced by altitude, the climate can also be classified on the basis
of above three parameters. National commission on agriculture
(1971) classified the country into 127 agro-climatic zones. The
planning commission has adopted agricultural Zones on the various
parameters for agricultural planning. The soil climatic zones can be
classified on the basis of rainfall, temperature and prevalent soil
types in the region.
Evapotransperation
Hobbins et al (2001) ststes that
evapotraspiration is climate controlled
and that with a dryer climate due to
osmosis there is a biological drive of the
balance of water density to be statbiled in
an equilibrium.
Humidity levels
Levels of water in the air
With high humidity can
cause asthma attacks and
aggravate other heath
conditions
Formula to work out
An approach to the determination of
recharge is to calculate actual (versus
potential) evapotranspiration (accounting
for processes such as soil-moisture storage
and direct evaporation) and determine the
amount of precipitation that passes through
the root zone (and thus becomes recharge).
The difficulty lies with determination of
actual evapotranspiration without extensive
field measurements. Due to shortcomings in
other methods for estimating reference
evapotranspiration, including the earlier
Blaney-Criddle FAO method, the FAO
developed an approach dubbed the FAO
Penman-Monteith equation (Allen and
others, 1998). The reference
evapotranspiration calculated with this
newer equation is then used with crop
evapotranspiration coefficients to estimate
crop-water requirements. The FAO
Penman-Monteith equation for calculating
reference evapotranspiration is: