Physical Factors Affecting Water Supply

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  • Created by: Amy Brown
  • Created on: 04-06-14 17:37
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  • Physical factors affecting water supply - Climate, River Systems and Geology
    • Climate
      • Regions near the equator receive high levels of annual precipitation
      • Equatorial areas such as the Amazon have 2 distinct periods of wet weather per year
      • Monsoon areas of Asia have 1 very wet season
    • River Systems
      • The worlds major rivers store large quantities of water and transfer it across continents
      • Rive flow increases down stream as more tributaries flow into the river
    • Geology
      • Where rocks underlying a river basin are impermeable - water will remain on the surface creating a high drainage density
      • Aquifers can store huge amounts of water underground
    • Case Study: Factors affecting California's water supply
      • Geographical Controls on water supply:
        • Mountain chains run parallel to the coast and prevent moist air reaching inland
        • Most rainfall falls in a coastal zone no more than 250km wide
        • South and far east of California receive under 100mm of rainfall due to the rain shadow cast by the Sierra Nevada mountains
        • High pressure systems over the Pacific ocean block moist air currents reaching southern California
        • Most of the major rivers are fed by snow melt from the Sierra Nevada mountains
        • In recent years extended through droughts have meant groundwater and surface storage levels gave decreased
      • Threats
        • Precipitation
          • Much of California is arid with annual average precipitation of between 200-500mm
            • 65% of precipitation is lost through evaporation, 13% flows out to sea = 22% for human use
          • 50% of the rain falls between November and March = seasonal shortages
        • Population
          • Grown from 2 million people in 1990 to 37.7 million in 2007
          • Spatial imbalance as 3/4 of demand for water comes from areas south of Sacramento - 75% of rain falls to the north
          • Increasing demands for water exceeds natural supplies
  • 65% of precipitation is lost through evaporation, 13% flows out to sea = 22% for human use




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