Cool waters and atmospheric high pressure

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1 QU: How does human activity contribute to drought risk? AIM: To evaluate the human influence of drought events in Africa's Sahel region. ST: What part of the ENSO cycle is at work here? What does it mean for Australasia and S. America? Ext: Can you state other global impacts of this cycle? Cool waters and atmospheric high pressure Warm water and atmospheric low pressure El answer Nino 1

2 Discuss: Why might the Sahel region be naturally drought prone? 2

3 Human activity and drought in the Sahel region, Africa. Task: 1 On an A3 sheet copy the above heading. 2 Cut out the images of Human causes in the Sahel region of Africa from your sheet. Explain how they contribute and use synoptic geography to explain links between them. The info below will help and the examples next slide. eg. Growing population + better technology to extract water = huge water deficits. Crops also involve land use change and which removes vegetation which reduces rainfall. (positive feedback loop) 3

4 e l p m a r o F x e 4

5 A Summary of your last task TASK: 1 Stick in your copy of the above. 2 Discuss in threes and add to a copy of the mind map below. How can human mismanagement lead to drought in wealthier areas of the world? Avery Hill? 5

6 But remember this can change between regions, due to accepted rainfall norms and levels of development. 6

7 Resource and extra reading slides 7

8 Sahel Rainfall Index The figure above is an index which displays the average amount of rainfall in the Sahel region. As seen in region A on the diagram, average rainfall is relatively above average, 0 being average, and may have lead to increased agricultural yields and livestock healthy. This excess of food may have in turn caused an increase in population as people in the Sahel procreate, perhaps in order to have more farmhands in the future. However, as seen in region B on the diagram, in the late 1960's rainfall began to fall quite deeply below average. Continued under average rainfall has contributed to aridity and has put the people of the Sahel at great risk to drought. Suddenly, negative consequences of higher population arise as food shortages will be imminent when drought occurs. This is what happened in 2010 during one of the worst droughts ever experienced in the Sahel. El Nino events can also influence drought in the Sahel as in 2015/16 8

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12 Impacts due to over abstraction Water availability problems occur when the demand for water exceeds the amount available during a certain period. They happen frequently in areas with low rainfall and high population density, and in areas with intensive agricultural or industrial activity. Apart from causing problems by providing water to users, over exploitation of water has led to the drying out of water courses and wetland areas in Europe as well as salt water intrusion in aquifers. In many areas of Europe, groundwater is the dominant source of freshwater. In a number of places water is being pumped from beneath the ground faster than it is being replenished through rainfall. The result is sinking water tables, empty wells, higher pumping costs and, in coastal areas, the intrusion of saltwater from the sea which degrades the groundwater. Saline intrusion is widespread along the Mediterranean coastlines of Italy, Spain and Turkey, where the demands of tourist resorts are the major cause of over abstraction. In Malta, most groundwater can no longer be used for domestic consumption or irrigation because of saline intrusion, and the country has resorted to desalination. Intrusion of saline water due to excessive extraction of water is also a problem in northern countries. Sinking water tables can also make rivers less reliable, since many river flows are maintained in the dry season by springs that dry up when water tables fall. Groundwater also helps sustain surface reservoirs of water such as lakes and wetlands that are often highly productive ecosystems and resources for tourism as well as leisure activities. These, too, are threatened by over abstraction of groundwater. Irrigation is the main cause of groundwater overexploitation in agricultural areas. Examples include the Greek Argolid plain of eastern Peloponnesus where it is common to find boreholes 400m deep contaminated by sea water intrusion. In Italy, overexploitation of the Po River in the region of the Milan aquifer has led to a 25m (even up to 40 m) decrease in groundwater levels over the last 80 years (Blue Plan, 2005). In Spain, more than half of the abstracted groundwater volume is obtained from areas facing overexploitation problems 12

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14 Fuelwood Main energy source Traditional technology to access groundwater relied on ropes and buckets in deep wells. The vast majority of rural water supply infrastructure is based on manual lifting of water, which has become a self regulating mechanism the rate at which groundwater can be lifted to the surface is limited by the physical capacity of the people using that well or borehole. This self regulating mechanism disappears as soon as people get access to external power sources. The source of the power does not matter wind, diesel fuel, electricity, and sunshine all allow people to lift more water more quickly from increasing depths. As Sub Saharan countries develop the rate of water extraction through new technologies is increasing and is unregulated. Locally water tables are diminishing adding to the aridity of some regions. Land use change in the Sahel