drought ppt

DROUGHT

WHAT IS DROUGHT?

Drought is a deficiency in precipitation over an extended period, usually a season or more, resulting in water shortage causing adverse impacts on vegetation, animals and people.

TYPES OF DROUGHTThere are three conditions that are generally referred to as drought:

Hydrological drought Agricultural drought Meteorological drought

HYDROLOGICAL DROUGHTHydrological drought  refers to deficiencies in surface and subsurface water supplies. It is measured as streamflow, and as lake, reservoir, and ground water levels.

This type of drought is all about the weather and occurs when there is a prolonged period of below average precipitation, which creates a natural shortage of available water.

METEOROLOGICAL DROUGHT

AGRICULTURAL DROUGHT

Agricultural drought

Occurs when there

isn’t enough waterfor a crop to grow at

a particular time.

CAUSES OF DROUGHT NATURAL CAUSES HUMAN CAUSES

Weather- increased amount of anticyclone weather means air holds less moisture and we get less rain

Global Warming- weather patterns change

Hotter weather- more evaporation than precipitation

El Nino- random weather event that reverses normal weather patterns (eg- Australia has years of drought + then years of floods).

Overpopulation- Too many people living in an area using too much water

Overcultivation- Planting a large number of crops that use too much water

Over extraction- Removing too much water from wells so they dry up

Deforestation- cutting down trees which otherwise store water + hold soil together.

EFFECTS OF DROUGHT Hunger and famine Thirst Disease Wildfires Social conflicts and wars Migration or Relocation

Preventive measures•Grow more trees•Develop irrigation facilities by building dams•Indulge in rain water harvesting•Spray water on the base of the plants so that less water is used•Grow drought resistant crops like millets, maize and sorghum•Build a canal to divert water•Put more wells and tubewells 

Case study – 1

1960s-1980s

•Natural climatic causes (low precipitation)•Deforestation•Desertification•Overgrazing•Overcultivation

CAUSES:

DEFORESTATION

When trees are cut down soil is more easily washed away.

OVERGRAZINGTraditional nomadic tribes settle in one place. Vegetation no longer protected the soil.

OVERCULTIVATIONCultivating the same land over and over again ruins soil quality destroying nutrients meaning nothing grows on it.

DESERTIFICATIONDesertificati-on occurs when land turns into a desert.

Impacts of desertificationPeople cannot find enough water or food for their cattle = FAMINECrops and cattle die.people are forced to leave their own country an take refuge in other countries – then are then known as refugees.Increase in sand stormsFlash floods

CASE STUDY - 2Australia Drought (2006)

CAUSES•Extremely low rainfall season across southern Australia.

•Poor use of water resources.

CONSEQUENCES

River Murray dried up in places.

•6 million sheep died in 2 years.•Temporary migrations•Improvement in use of water resources•Eventual floods

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