All About Groundwater

By Hannah Johnson

So what is groundwater?

Groundwater, as the name implies, is water found underground in the cracks and spaces of soil, sand and rock.

The processes of water entering and leaving the groundwater system are known as recharge and discharge. Both of these processes can occur naturally, or they can be influenced by human activity.

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Porosity vs. Permeability

Porosity is a measure of the empty spaces in a material.

Permeability is a measure of a material's ability to allow fluids to pass through it.

The higher the porosity and permeability of a material, the more readily groundwater will flow through it. A material with high porosity will hold more groundwater, and a material with high permeability will allow groundwater to flow more quickly through it.

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The Water Table

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The zone of aeration is the upper area in the ground in which the pore spaces are filled mostly with air.

The zone of saturation is the lower area in the ground in which the pore spaces are filled mostly with water.

The water table is found between the zone of aeration and the zone of saturation. Below it, the ground is saturated with water (the zone of saturation.)

An aquiclude is an impermeable material which acts as a barrier to the flow of groundwater.

An aquifer is a body of saturated rock through which water can easily move.

Three main types of aquifers

An unconfined aquifer has no confining layers between the zone of saturation and the land surface.

A confined aquifer is covered by a confining layer of aquitard, which is material with little or no permeability.

A perched aquifer is a saturated zone within the zone of aeration. It sits on a confining layer above the water table.

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Effects of depleting groundwater & California's Drought

California's Drought: Groundwater at risk

Main ways we pollute groundwater in the US

Point source pollution comes from a specific source while nonpoint source pollution comes from diffuse sources.

  • Storage tanks (point)
  • Septic systems (point)
  • Uncontrolled hazardous waste (nonpoint)
  • Landfills (point)
  • Chemicals and road salts (nonpoint)
  • Atmospheric contaminants (nonpoint)
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