Droughts

What Is A Drought?

• An extended period of months or years when a region notes a deficiency in its water supply.

• Occurs when a region receives consistently below average precipitation.

• Substantial impact on the ecosystem and agriculture of the affected region.

Causes

• Rainfall is related to the amount of water vapor in the atmosphere.

• This is combined with the upward forcing of the air mass containing that water vapor.

• If either of these are reduced, the result is a drought!

• Can be triggered by an above average prevalence of high pressure systems.

Causes Cont.

• Human activity can directly trigger events helping in the formation of a drought.

• Examples include over farming, excessive irrigation, deforestation, and erosion.

• Impact on the ability of the land to capture and hold water.

• Along with drought in some areas, flooding and erosion will increase in others

A few Common Consequences • Diminished crop growth or

yield productions.• Dust Bowls- themselves a sign

of erosion.• Dust Storms- when drought

hits an area suffering from desertification.

• Famine- due to lack of water for irrigation.

• Habitat Damage- affecting both terrestrial and aquatic wildlife.

• Wildfires- such as Australian bushfires, are more common during times of drought.

• Mass Migration- resulting in internal displacement and international refugees.

• Reduced Electricity Production- due to insufficient available coolant for power stations.

• Shortages of water for industrial users.

• Social unrest.• War- over natural resources,

including water and food.

Stages Of Drought

• As a drought persists, the conditions surrounding it gradually worsen.

• Its impact on the local population gradually increases.

Stage 1

• Meteorological- drought is brought about when there is a prolonged period with less than average precipitation.

• Meteorological drought usually precedes the other kinds of drought.

Stage 2

• Agricultural- are droughts that affect crop production or the ecology of the range.

• This condition can also arise from any change in precipitation levels when soil conditions and erosion triggered by poorly planned agricultural endeavors cause a shortfall in water available to the crops.

Stage 3

• Hydrological- drought is brought about when the water reserves available in sources such as aquifers, lakes and reservoirs falls below the statistical average.

• This can be triggered by more than just a loss of rainfall.

Stage 4

• Socioeconomic- how the water shortage affects the people living in the affected area

• On average droughts cost the US $6-8 billion annually compared to $2.4 for floods and $4.8 for hurricanes

• Seldom produce structural damage so effects may be less obvious

Drought Mitigation Strategies

• Cloud seeding.• Desalination of sea water

for irrigation or consumption.

• Drought monitoring - Continuous observation of rainfall levels

• Land use - Carefully planned crop rotation can help to minimize erosion.

• Rainwater harvesting -• Recycled water - Former

wastewater (sewage) that has been treated and purified for reuse.

• Transvasement- Building canals or redirecting rivers as massive attempts at irrigation in drought-prone areas.

• Water restrictions

Droughts vs. Heat Waves• Some people think that

they are the same thing.• Heat Wave- a prolonged

period of excessively hot weather.

• No universal definition of a heat wave

• The term is relative to the usual weather in the area.

• Just because there is a heat wave doesn’t mean there is a drought.

Range of Effects for Droughts

• Droughts affect people on a national, local, and a global range.

• When a drought is in effect everyone can be affected.

• Droughts can even affect the economy and jobs of other countries.