Case study: Factors affecting California's water supply

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  • Case Study: Factors affecting California's water supply
    • Geographical Controls on water supply
      • 1.Mountain chains run parallel to the coast and prevent moist air reaching inland
      • 2.Most rainfall falls in a coastal zone no more than 250km wide
      • 3.South and far east of California receive under 100mm of rainfall due to the rain shadow cast by the Sierra Nevada mountains
      • 4.High pressure systems over the pacific ocean black moist air currents reaching southern California
      • 5.Most of the major rivers are fed by snowmelt from the Sierra Nevada Mountains.
      • 6.In recent years extended droughts have meant groundwater and surface storage levels have decreased
    • Threats
      • Percipitation
        • 1.Much of California is arid with annual average percipitation of between 200-500mm
        • 2.65% of percipitation is lost through Evapotranspiration, 13% flows out to sea= only 22% for human use
        • 3.50% of rain falls between November and March= seasonal shortages
      • Population
        • 1.Has grown from 2 million people in 1900 to 37.77 million in 2007
        • 2.Spatial imbalance as three quarters of demand for water comes from areas south of the Sacramento- 75% of rain falls to the north
        • 3. Increasing demands for water exceed natural supplies


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