- PowerPoint Presentation

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The Water Cycle

Click here for an animation

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Increase in runoff with urbanization

Decrease in infiltration

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Groundwater

is simply water under the ground where the soil is completely filled or saturated with water. This water is also called an

aquifer.

Groundwater

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Water

movement

is slow and might move anywhere from less than a millimeter up to a mile in a day.

Groundwater moves underground from areas where the elevation is high, like a hilltop, to places that are lowland areas.

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Groundwater

Where the water table meets the land surface, a

spring might bubble up or seep from the ground and flow into a lake, stream, or the ocean.

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Groundwater

Ground water that meets the land surface also helps keep rivers, streams, lakes and wetlands

filled with water.

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Zone of Aeration:

area where the pore spaces in the rock/soil are empty of water

Zone of Saturation

: area where the pore spaces in the rock/soil

are filled with water

Water Table

:

boundary between zone of saturation & zone of aeration; wells must

go below the water table to reach water

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Porosity and Permeability

Permeability

: how quickly water can travel through a material

Porosity

: the percent of a material’s volume that is pore space

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Groundwater

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Dangers Associated with Groundwater

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Effects of Over-Pumping a Well

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Sinkholes from groundwater overpumping, Antelope Valley, CA

Dust storm during Dust Bowl in Kansas, when overpumping from wells & a drought caused farmers to ‘overspend’ the water budget

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CONTAMINATED?!

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Caves

Limestone

is a common bedrock that dissolves more easily than some types of rock. The carbonic acid found in groundwater dissolves the

calcite found in limestone. Chemical weathering changes the calcite into clay increasing the porosity of the limestone left behind.

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Caves

Over time as more and more water flows through cracks in the limestone bedrock, the carbonic acid

dissolves

the limestone and carries it away in solution. After thousands of years, these cracks become larger eventually forming a network of underground tunnels

. These caverns, or caves can be many miles long and hundreds of feet deep.

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Cave Formations

When water drips from the roof of a cave, calcite is deposited. Slender deposits called stalactites hang like icicles from the roof. On the cave floor beneath the stalactites, a rounded mass called stalagmites form. When they meet, a column

is formed.

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Entrance to Mammoth Cave National Park-Kentucky

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Soda Straws

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Helictites

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Chandeliers

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Flowstone is sheet-like which includes draperies/curtains.

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Cave “Bacon”

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Luray Caverns, VA

Observe an animation of cave formation.

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Karst

Topography

They are regions characterized by caves, sinkholes

, lost rivers or sinking streams

, and underground drainage.

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Karst

Topography forms in areas with bedrock made of calcite like

limestone (or dolomite).

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Karst

areas of the U.S. shown in green.

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Step 1

: Acidic groundwater dissolves limestone. Then the water table drops, leaving empty caves.

Development of Karst Topography

Step 2

: Ground above the caves is eroded away.

Step 3

: Thin rock above the cave collapses, creating a sinkhole.

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Winter Park, FL

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Sinkhole, Shenandoah Valley, VA

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Because

rainwater drains through sinkholes, there are few surface rivers in

Karst

regions

.

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Lost

or

sinking

streams

form when the surface stream disappears underground and flows out of a cave many miles away.

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Artesian Formation

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Artesian Well