Groundwater
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Groundwater Ground water does not occur as an underground ______ UNLESS it is found in a cave.
description
Groundwater. Ground water does not occur as an underground ______ UNLESS it is found in a cave. Most groundwater occurs in small ________________ within rock and unconsolidated sediment Water flows through this sediment __________…. A few centimeters to meters per _______. - PowerPoint PPT Presentation
Transcript of Groundwater
Groundwater Ground water
does not occur as an underground ______ UNLESS it is found in a cave.
So where is groundwater
stored and what does it look like?Most groundwater occurs in
small ________________ within rock and unconsolidated sediment
Water flows through this sediment __________…. A few centimeters to meters per _______.
Groundwater tends to collect above materials that are ______________.
Porosity___________
The amount of space in between sediment grains, cracks or fractures in rocks.
These spaces may be filled with _____, air or a mixture of both.
What kind of material has the highest porosity?
Sediment Porosity % Gravel 25 to 40
_________ 30 to 50
Silt 35 to 50
__________ 35 to 80
Glacial Till 10 to 20
More about Porosity
PermeabilityThis is the ability to ___________ water. Rocks may have high porosity, but if
the spaces or pores are _________________, then the permeability will be very _____.
Materials that can transmit large quantities of water beneath the surface are called ___________.
Recall what types of material have the highest ____________.
Sediment Porosity (%)
Gravel 25 to 40 Clean Sand 30 to 50 Silt 35 to 50 Clay 35 to 80 Glacial Till 10 to 20
What kind of materials have a high permeability?
Distribution of Water
Distribution of Groundwater Unsaturated Zone – Region that covers the ground surface
down to the ___________________. This area may have pore spaces that are partially filled with _____________. The unfilled pore space contains air.
Saturated Zone – Region of the subsurface where the pore spaces are completely filled with water.
______________ – Area where the unsaturated and saturated zones meet in unconfined aquifers. (Very top of the saturated
zone)
_______________ – Area above the water table where capillary forces pull water into pore spaces.
Bedrock
Bedrock
Bedrock
Clay
What is the difference between these to aquifers?Hint: Compare their layers
Confined Aquifer- Aquifer is between 2 layers of ___________ matter.Water is pressurizedWells are called ____________ wells
Unconfined Aquifer-Water is not confined on the top and bottom of saturated zone.Water can freely move to the surface if the water table rises.The level of the water in a well will be the _____________ as ground water level.
Describe the difference of water flow with respect to the streams
and the water table in the diagrams below
Confined groundwater may flow at the surface due to hydrostatic pressure.
______________Water flows freely from the ground surface.This happens when the water table intersects the ground surface.
Perched Aquifer
Observe a geyser animation along with an explanation of how a geyser occurs by clicking on Beehive geyser above.
Wells We use wells to
remove groundwater.
The water table goes down when water is pumped from a well. This is called a cone of depression.
Artesian – Groundwater that is under ___________ rises above
the level of the aquifer.1. One end of the ___________ aquifer, must be able to receive
water2. There must be ___________ above and below the aquifer.
If the water does not rise to surface level we call this artesian well a_______________ artesian well.
When a well is drilled into the aquifer and water rises to surface level or higher, then we have a ___________ artesian well.
Over-pumping can be a real problem in areas of slow recharge.
When the groundwater is not recharged at the same rate or faster than groundwater is removed, the water table is ________, wells dry up, and there is an overall depletion of groundwater.
Non-renewable resource in some areas – Can be referred to as groundwater mining.
In the US there is a huge problem with over pumping in the Southwest and Southern California.
SubsidenceWhen groundwater is over pumped, there is no longer the pressure of water between the pore spaces of unconsolidated material. The overlying material puts lots of weight on this material causing the grains to pack tightly together and the surface to collapse.
Click on the picture to link to more information
Sink Holes http://ga.water.usgs.gov/edu/
sinkholes.html
Florida Sinkhole
Cave
Cave
To see an animation of how a cave is formed, click on the image below
What are each of these features?
A B C D
What are each of these features?
A B C D
What are each of these features?
A B C D
What are each of these features?
A B C D
