Groundwater

Groundwater constitutes approximately _______% of the hydrosphere.

The single greatest use of groundwater in the US is for .

U.S. Groundwater Withdrawals1950–1995

Use of Groundwater in Texas (constitutes ____%* of all water used instate)

80% ** - Agricultural (mainly irrigation)

15% ----- Municipal

5% ------ Industrial

* projected to be 31% by 2050

** projected to be 59% by 2050

The ______________________ is

• The top of the saturated zone of groundwater

• The level to which water will rise in a hole

• The level to which water will rise in an unconfined aquifer

Groundwater Table (fig. 17.2)

The Saturated Zone is:

The Unsaturated Zone is:

Groundwater flows from areas of water table (or pressure) to areas of water table (or pressure). (fig. 17.5)

In humid regions, ground water can flow into (or recharge) streams as:

In humid regions, the water table is a subdued replica of the surface topography.

During droughts:

During wet periods:

Sketch a water table:

1) before pumping (fig. 17.13)

2) with a cone of depression cause by pumping (fig. 17.13)

3) after excessive pumping.

Sketch how your neighbor’s pumping can result in your well becoming contaminated. (fig. 17.21)

How can pumping fresh water from a coastal well result in saltwater intruding and contaminating that well? (fig. 17.19)

The slope of the water table is called the ____________________. (fig. 17.6)

Q. Of what value is a contour map of water table elevations? (fig. 17.3)

A.

is used to determine the velocity of ground water

Vg = K S
p

\

Vg = velocity of groundwater

K =

S =

p =

________________: The percent void space in a rock or sediment. It is a measure of the potential volume of water that can be stored in a rock

________________: The ability of a material to transmit a fluid. It is a measure of how fast the fluid can travel through the rock or sediment

Rates of groundwater movement are slow to very slow (depending on permeability), generally within the range of 10 to100 cm per day

Examples of land uses that might cause groundwater pollution. (fig. 17.22)

Q. Are you more likely to contaminate a well pumping from a cavernous limestone or a sandstone, and why? (fig. 17.20)

Aquifer:

Aquitard:

Q. What makes a good Aquifer?

A. The ability to store large amounts of water that can be removed easily, as measured by:

_____________

_____________

Examples:

Porous Sand

Well-sorted Sand

Poorly-sorted Sand

Well sorted Sand verses well sorted Gravel

Cemented Sandstone

Un-fractured Shale

Fractured Shale

Aquifer Characteristics

Rock Type	Porosity	Permeability
Gravel
Well-sorted sand
Poorly sorted sand
Well-sorted sandstone
Fractured shale
Limestone

The two types of aquifers are:

_________________ Aquifers

_________________ (or Artesian) Aquifers

An__________________ aquifer is exposed at the land surface.

A ___________________aquifer is overlain (confined) by an aquitard.

The of a confined aquifer is the area where rainfall enters (recharges) the aquifer.

The of is the level to which water will rise in wells in confined aquifers.

The city water supply can be thought of as an artificial Artesian System (fig. 17.17)

Confined Aquifer

What is the difference between a flowing and non-flowing artesian well? (see fig. 17.15)

Given a cross section, could you locate a (an)

- Unconfined aquifer?

- Non-flowing artesian well?

- Flowing artesian well?

- Dry well?

Average Annual Precipitation in the U.S.

How does average annual rainfall vary across Texas?

The three main aquifers in Texas are:

1)

2)

3)

Cross Section of the Gulf Coast Aquifer near Houston

Where is the recharge area for the ground water used by Houston?

Pumping of water from a shallow confined aquifer results in dewatering of adjacent clays. So?

How did the Brownwood Marsh (and bird sanctuary) form?

What happened in the San Joaquin Valley? (Box 17.3)

What is the Edward’s Aquifer, and why is it’s recharge zone “environmentally sensitive)

What was San Antonio like 120million years ago?

What happened approximately 30 million years ago?

Draw and label a cross section of the San Antonio/Austin area today.

What’s the big deal about the Edwards Aquifer?

Where is the Ogallalla Aquifer located? (Box 17.2)

Is it a confined or unconfined aquifer?

What’s the big deal about the Ogallala Aquifer?