GroundwaterGroundwater

BIGBIG Idea: Idea:

•PrecipitationPrecipitation and and infiltrationinfiltration contribute to contribute to groundwatergroundwater, which is stored , which is stored in underground reservoirs in underground reservoirs until it surfaces as a spring or until it surfaces as a spring or is drawn from a well.is drawn from a well.

Infiltration:Infiltration:

• process of water process of water moving into the moving into the soil/groundsoil/ground

• to penetrate, to penetrate, enter or gain enter or gain accessaccess

I. Water Beneath the I. Water Beneath the SurfaceSurface

Groundwater:Groundwater: underground underground water that fills almost all of water that fills almost all of the the pores pores in rock and in rock and sedimentsediment

AquiferAquifer: : a body ofa body of rockrock that can that can store water and also let water store water and also let water

flow throughflow through

Think of an AQUIFERAQUIFER as a…• large, horizontal spongesponge that

absorbs and transports water along its length

A. Rock Properties that A. Rock Properties that Affect GroundwaterAffect Groundwater

Porosity

Permeability

1. Porosity: percentage of open spaces in a rock or sediment

FACTORS THAT INFLUENCE FACTORS THAT INFLUENCE POROSITY:POROSITY:

(a) SORTING: amount of uniformity in particle size

HIGH pore space LOW pore space

(b) SHAPE:(b) SHAPE: rounder particles = more porous

(c) PACKING:(c) PACKING: loosely packed = more porous

2. Permeability: how freely water flows through open

spaces in a rock (the pores must be connected)

Impermeable – water can NOT flow through

Can something be porous Can something be porous but impermeable?but impermeable?

• The cork end is The cork end is red because the red because the grape juice went grape juice went into it. Does this into it. Does this mean it is mean it is porous?porous?

• If you turn the If you turn the bottle upside bottle upside down will it leak? down will it leak? Is the cork Is the cork permeable?permeable?

B. Zones of GroundwaterB. Zones of Groundwater

1. 1. Zone of Saturation:Zone of Saturation: the layer the layer of ground where all the pores of ground where all the pores are filled with water.are filled with water.

2.2. Water Table: Water Table: upper surface upper surface of the zone of saturationof the zone of saturation

3. 3. Zone of Aeration: Zone of Aeration: upper region, upper region, where water is both in the soil and where water is both in the soil and seeping down to the water table.seeping down to the water table.

Zone of Aeration

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• Capillary Action: ability of water to rise UP the soil.

• Smaller particle size = greater capillarity

Capillary Fringe:Capillary Fringe: middle layer, middle layer, between the water table and the between the water table and the

zone of aeration.zone of aeration.

C. MOVEMENT OF C. MOVEMENT OF GROUNDWATERGROUNDWATER

• Depends on:

1.Permeability of the aquifer• ↑ permeability = ↑ velocity

2.Gradient of the water table• Gradient = steepness of the

slope• ↑ gradient = ↑ velocity

II. Wells and SpringsII. Wells and Springs

• Water Table:Water Table: upper layer of upper layer of rocks with all pores filled with rocks with all pores filled with water.water.

A. Ordinary Well:A. Ordinary Well: A hole dug A hole dug below the water table which below the water table which fills up with water.fills up with water.

Cone of Depression: Cone of Depression: lowered lowered area of the water table due to area of the water table due to

pumpingpumping

B. Artesian Wells: water flows freely with no pumping

• Underground water under pressure (between two impermeable rock layers) rises to the surface

• Water is naturally filtered as it passes through porous rock and seeps to surface

III. Groundwater and III. Groundwater and Chemical WeatheringChemical Weathering

A.A. Caverns:Caverns: rocks rich in calcite rocks rich in calcite (limestone) slowly dissolved (limestone) slowly dissolved by carbonic acid.by carbonic acid.

• Hard water = many Hard water = many dissolved minerals (Ca, Mg, dissolved minerals (Ca, Mg, Fe)Fe)

• Soft water = few dissolved Soft water = few dissolved mineralsminerals

Luray Caverns, VA

•Formation of a Cave

1. Stalactites:1. Stalactites: water with water with dissolved calcite runs from a dissolved calcite runs from a cave’s cave’s ceilingceiling and solidifies and solidifies downward.downward.

2. Stalagmites: 2. Stalagmites: calcite rich calcite rich water drips on the cave’s water drips on the cave’s floorfloor and builds upward. and builds upward.

If the If the two two connect, connect, then it then it forms a forms a columncolumn..

3. Natural 3. Natural Bridge:Bridge: when when the roof of a the roof of a

cavern cavern collapses in collapses in

several places several places leaving an leaving an

arch- shaped arch- shaped rock.rock.

B. KARST TOPOGRAPHYB. KARST TOPOGRAPHY• regions where chemical weathering by

groundwater is now visible at the surface

• regions where it is humid and there are limestone formations near the surface

• Virginia, Kentucky, Tennessee, Indiana, and Florida have Karst Topography

1. Sinkholes 1. Sinkholes (the main (the main feature of Karst feature of Karst

Topography)Topography)

How do sinkholes form?How do sinkholes form?

• Rain seeps through soil and absorbs Rain seeps through soil and absorbs carbon dioxide and reacts with carbon dioxide and reacts with decaying vegetationdecaying vegetation

• Acidic water is createdAcidic water is created• Water moves through spaces and Water moves through spaces and

cracks undergroundcracks underground• Limestone is slowly dissolved, Limestone is slowly dissolved,

creating network of cavities and voidscreating network of cavities and voids• Pores and cracks enlargePores and cracks enlarge• Land surface above collapses or sinksLand surface above collapses or sinks

2. Streams that disappear 2. Streams that disappear in the groundin the ground

Like Lewis Creek in Staunton

3. Caverns and Caves3. Caverns and Caves

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