Groundwater

TPO28第一篇Groundwater，托福®考试是一个由ETS测评研发的学术英语语言测试 ，托福®考试通过考察听、说、读、写这4个技能方面以体现参与者在学术语言任务环境下的真实学术语言能力，并可用于本科及研究生阶段的院校申请。 托福是“对非英语国家留学生的英语考试”（Test of English as a Foreign Language）英文缩写（TOEFL）的音译。

Groundwater

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• Para 1 lead in
  • information about groundwater
    • stored in pores and fractures in rocks
    • 50 times as much water under ground than above ground
    • the deeper, the less water rocks can occupy
• Para 2 Aquifers, Porosity and Permeability
  • Aquifers A groundwater reservoir from which water can be extracted
  • Porosity
    • pore space between sediment grains that can be filled with water
    • expressed as a percentage of the total rock volume
  • Permeability
    • the ability of water to flow through the interconnected pore spaces
• Para 3 Sediment sorting
  • poorly sorted& tightly compacted→low porosity and permeability
  • sedimentary rocks
    • contain the most space→most connom reservoirs
  • sandstones
    • good aquifers
  • finer-grained mudstones
    • impermeable
  • Igneous and metamorphic
    • more compact, no space between
    • may become groundwater reservoirs if extensive fracturing occurs and the fracture system is interconnected
• Para 4&5: water table
  • the underground boundary below which all the cracks and pores are filled with water
  • reach the Earth's surface→rivers, lakes and marshes
  • usually follows the contours of the topography
  • vadose zone
    • above the water table
    • where rainwater percolates
    • supplies plant roots near the surface with water