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- Overview of drought
- Causes of drought
- Impacts of drought
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Human Causes
Deforestation causes drought because it prevents plants from nourishing the earth. The fibrous roots of plants absorb and hold considerable amounts of water which is slowly released into the soil. during the dry season water will treacle down the channels beside the fields. But when the plants are removed and the crops are harvested, the supply of water dries up.
Global warming influences the statistical frequency and severity of droughts in Australia. The warmer temperatures cause greater evaporation, particularly during summer, which can increase the chances of wildfires. It is said that conditions will become drier in the southern half of Australia and wet years will become less frequent in the next 50 years or so. Burning fossil fuels contribute to global warming.
The growing population of human beings has increased the amount of water being used, which has subsequently lead to a higher demand for water. More people on earth means more food needs to be produced, therefore more water is needed for crops etc. As population continues to rise, the demand for water will also increases.
Too many fertilizers are being used by people which can cause the soil to loose its moisture and richness. Overgrazing, improper soil management, and poor crop selection can also stress local water supplies.
Natural Causes
Geographical factors make Australia particularly drought-prone. Most of the country gets low, highly erratic rainfall due to a climate phenomenon called the Southern Oscillation, which is a shift in air pressure between Asian and East Pacific regions.
Many of Australia’s widespread droughts are related to an El Niño event. In a typical year, warm air is blown west across the pacific towards Australia, bringing heavy rain to Northern Australia. When an El Nino occurs, these winds and surfaces ocean currents reverse their direction. The warm, moist air is pushed towards South America. This produces rain in South America and drought in Australia.
Droughts also occur during shifts in global wind patterns that allow widespread high-pressure systems to persist over land for weeks, months, or even years. In high-pressure systems, air sinks, or subsides. Subsiding air prevents moisture in the air from rising, so clouds cannot form. The dry conditions continue until the high-pressure system gets shifted out of the way.
Ridges of high pressure areas form with behaviours which prevent or restrict the developing of thunderstorm activity or rainfall over a certain region