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Drought (Hazards (subsidence as groundwater levels dropped causing land to…
Drought
Hazards
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contamination of land and drinking water by seawater, drawn inland by lack of pressure
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water shortage for residents. In developing countries people might switch to unclean water and get cholera etc.
Aridity vs Drought
In arid areas, the climate is dry due to high pressure and low rainfall
The factors that affect whether an area will get drought are: how and when it gets precipitation (rainy season? and summer/winter respectively (soil in winter absorbs rain more easily))
Arid
Permanent low precipitation, like the Sahara
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Drought
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In the UK, drought is 15 days without rainfall
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California
(developed)
January 2014, low rainfall and overuse of the Colorado River caused a drop in water supplies
Impacts
Ecosystems
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Wildfires cause environmental damage, air pollution and wildlife and habitat destruciton
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Namibia (developing)
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Impacts
People
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Harvest yield was far less than 2012, so food shortages
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Environment
Large areas of Namibia are changing from savannah grasslands to desert due to lack of rainfall. Only drought-resistant plants can grow, but livestock can't graze on them
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Response
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Organisations
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The Lutheran Church helped by providing basic food, a safe environment and clean water
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Causes
Natural
Hydrological: the hydrological cycle receives less rainfall than normal: less rainfall means less groundwater supplies and reservoirs are not refilled, causing drought conditions
Meteorological: an area receives less precipitation than normal. In the UK, high pressure forces away low pressure systems that bring rain, which means no rain
Human
Deforestation: trees reduce evaporation, store water and add to atmospheric moisture by transpiration
Dam building: restricts the flow of water in the river, lowering water levels and volume, causing drought conditions further downstream
Agriculture: if there is not enough water in the area to support the crops grown by farmers, especially if farmers use irrigation to start growing crops that require more water than is available
Global circulation makes some locations more vulnerable to drought. Like where the Hadley and Ferrel circulation cells are, like Africa's Sahel, descending dry air means less rainfall. Rainfall there only occurs in a season, if the season doesn't happen then drought happens