Groundwater Notes

Groundwater

Groundwater Basics

  • Only about 3% of Earth's water is fresh water.
  • About 25% of fresh water is stored as groundwater.
  • Groundwater is accessed as precipitation falls and soaks into the ground.

How Water Moves Underground

  • Water movement depends on soil and rock layers.
  • Water flows through permeable materials but is blocked by impermeable materials like clay or granite.
  • Permeable: Water can flow through it.
  • Impermeable: Water cannot flow through it.

Groundwater Zones

  • Saturated Zone: Permeable material filled with water above an impermeable rock layer.
  • Water Table: The top of the saturated zone where water begins to collect.
    • The top of the water table is a flat surface where the water gathers.
  • Unsaturated Zone: Area above the water table containing moisture and air.

Accessing Groundwater

  • Spring: Groundwater flows naturally to the surface where the surface is lower than the water table.
    • They form when an area gets too full of water to hold any more.
    • They are typically safe and fresh to drink.
  • Hot Spring: Springs heated by magma.
  • Geyser: Vent in the Earth's surface that ejects hot water and steam.
    • The pressure builds and causes the geyser to erupt through a crack or opening in the ground.
  • Aquifer: Underground layer of rock or sediment holding groundwater, made of permeable materials.

Wells

  • Wells: Bring groundwater to the surface.
    • Wells need to be drilled down below the water table.
  • Artesian Well: A well where groundwater is trapped between impermeable layers, creating pressure that forces water to the surface without a pump.

Earth's Hydrosphere

  • Hydrosphere refers to the total amount of water on Earth.
  • Water flows within the three areas: on, above, and below earth's surface, in a cycle.
  • Flux: The process of water moving in and out of a system or area, with inflow referring to water moving in, and outflow describing water moving out.
  • Water Budget: Description of the amount of inflows and outflows in a system or area.
  • When inflow and outflow are equal, the system or area is in a steady state, and we say that the water budget is balanced.
  • Inflow may come from precipitation in the form of rain, sleet, or snow and injection wells.
  • Outflows may be caused by evaporation and transpiration, and pumping water out of the ground.
  • Scientists use water budgets to assess a system's or area's water balance and determine the effect of human activities on an area's water budget.
  • The two main fluxes of water on Earth are precipitation which is the main inflow, and evaporation, which is the main outflow.
  • Earth's water budget is balanced, so the mass of water on Earth remains constant.