Ground Water

1
Ground Water

• Ground water is water found in the upper
  portion of Earths crust below the surface of
  the ground. This water is most common within
  sediment and Sedimentary rock.

• Igneous and Metamorphic rocks only contain a
  little ground water in its cracks. These two
  rock types seldom have pore space and thus
  rarely hold and transmit ground water.

Reference Tarbuck and Lutgens Pages 105 -
110
2
Facts Regarding Groundwater

• Ground water is the second largest freshwater
  resource, with ice being the largest.

• Of all the liquid fresh water on Earth, 94
  is groundwater.

• Groundwater is the largest freshwater
  reservoir readily available to humans.

• Groundwater provides drinking water for more
  than 50 of the human population.

• Groundwater is an equalizer of stream flow.

• Groundwater resources are threatened by
  1) overuse (pumping - irrigation and
  human consumption) 2) groundwater
  contamination (sewage from septic tanks,
  agriculture chemicals, and landfills)

3
Ground Water and the Water Table
The source of ground water is rainfall. When
rain falls to the ground it enters the pores in
the soil and sticks to the particles. If enough
water falls to Earth, the water will continue
downward until it reaches an impermeable layer of
rock or clay.
4
Ground Water and the Water Table
5
Ground Water and the Water Table
Depth depends on the following factors
1) amount of rainfall 4) slope of the grounds
surface 2) seasons 5) thickness of the soil
. 3) climate 6) time between rainfalls
6
Depth of the Water Table
The water table rises and falls depending on the
amount of rainfall, climate, and season.
For example, refer to the diagrams below
7
Sample Problem
With the aid of diagrams, explain the effect of a
drought on the water table.
Answer Water table lowers during a drought (dry
season) because the rate of withdrawal is greater
than the rate of recharge. Groundwater will move
out of the ground and in to streams and ponds.