Xplain How Human Interference in the Water Cycle Can Affect Water Availability.

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Q. Explain how human interference in the water cycle can affect water availability. A. Human interference on the hydrological cycle are not new, however, as populations grow, countries standards of living rise, there is increasingly more impact on all aspects of the hydrological cycle. The majority of the interference is negative, but some is positive. Water use varies considerably between continents. On average, North America uses 400 litres per person per day. Europe uses 200, Asia and Latin America use between 200 and 400 and the sub-Saharan desert uses just 10-20 litres per person per day. Overall, 70% of water is used for farming while industry and municipal uses account for 22 per cent and 8 per cent. The use of aquifers (water bearing rocks) to supply water is widespread. However, if the use of groundwater exceeds the recharge of groundwater, the wateR table drops. Human activity affects not only the quantity of groundwater but also the quality. One of the main problems of groundwater abstraction is in coastal areas, namely salt-water intrusion. This is the movement of salt water into an aquifer that previously held fresh water. Salt-water intrusion is sever along the Mediterranean, Black Sea and Baltic coasts. Tundra landscapes hold vast quantities of the worlds freshwater as permafrost. Changes in temperate and the melting of permafrost can have significant impacts on the availabity of water. Urbanisation increases the amount of impermeable surfaces, which in turn reduces the amount of infiltration and percolation. The high drainage density associated with the network of drains, gutters, sewers and flood relief channels, quickly carries water into river channels, therefore increasing channel storage. Moreover, water quality is affected by urbanisation. Overland flow in urban areas picks up suspended solid particulate matter and dissolved chemicals,
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