LESSON 9.9 What are the causes and impacts of droughts and flooding rain?
LEARNING INTENTION By the end of this lesson you should be able to: • explain the causes of droughts and/or floods • describe the impact of droughts and/or floods on people and the environment • suggest strategies for managing drought and / or flood events.
Tune in FIGURE1 shows Menindee Lakes, nine large, shallow lakes in southwest New South Wales on the Darling River.
FIGURE1 Menindee Lakes, a series of lakes along the Darling River, shown during rainy and drought conditions.
Identify the similarities and differences between the two photos.
9.9.1 What is a drought? Australia, the driest inhabited continent, lies in a high-pressure region with dry, stable air. Rainfall varies widely, influenced by the Southern Oscillation and El Niño (see lesson 9.6 extensive). Drought conditions occur when high-pressure systems are more extensive than usual, creating rainfall shortages. Drought means below-average rainfall, when there is not enough water to meet our needs. Water needs differ so, for example, Sydney might experience drought with more rain than Alice Springs during above-average rainfall. Droughts vary in timing and duration, like the short 1982–83 drought and the longer Millennium Drought. Different weather systems make nationwide droughts rare. Drought can have a devastating impacts on both people and the environment. They can be relatively brief or last for years or decades. 9.9.2 Causes and impacts of the Tinderbox Drought The Tinderbox Drought (2017–19) was a severe drought that affected southeastern Australia. It was characterised by extremely dry conditions, high temperatures and a dry atmosphere. This drought was driven by unusual air movement in the atmosphere, which disrupted normal weather patterns. As a result, moisture was diverted away from southeastern Australia to northern Australia. When combined
TOPIC9 Water in the world 297
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