Aquifers 101
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Aquifers 101. Robert E. Mace Texas Water Development Board Groundwater 101 November 10, 2010. Outline. Yay for aquifers! Definitions Flow through an aquifer Pumping an aquifer. Outline. Yay for aquifers! Definitions Flow through an aquifer Pumping an aquifer. World Water Balance.

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Aquifers 101

Aquifers 101

Robert E. Mace

Texas Water Development Board

Groundwater 101November 10, 2010


Outline

Outline

  • Yay for aquifers!

  • Definitions

  • Flow through an aquifer

  • Pumping an aquifer


Outline1

Outline

  • Yay for aquifers!

  • Definitions

  • Flow through an aquifer

  • Pumping an aquifer


World water balance

World Water Balance

From Freeze and Cherry (1979)


Groundwater and texas

groundwaterandTexas

  • ~60 percent of the 16.6 million acre-feet of water used

  • ~80 percent of groundwater is used for irrigation

  • groundwater provides 39 percent of water to cities

  • tastes good when yer thirsty


Aquifers 101

austinchalk


Aquifers 101

  • catfish farm wellEdwards aquifer

  • flowing well at 40,000 gpm

  • 1/4 of San Antonio’s use

  • 9% of Annual Recharge

  • world’s largest artesian well

  • National Geographic (1993)


Aquifers 101

Major aquifers


Aquifers 101

Minor aquifers


Aquifers 101

Hickory Aquifer, sandstone


Aquifers 101

Edwards-Trinity (Plateau) Aquifer, limestone


Aquifers 101

Ogallala Aquifer, sand and gravel


Outline2

Outline

  • Yay for Groundwater!

  • Definitions

  • Flow through an aquifer

  • Pumping an aquifer


Definitions

Definitions

  • Aquifer

  • Aquitard/confining layer

  • Vadose zone/unsaturated zone

  • Water table

  • Recharge

  • Water level

  • Unconfined aquifer

  • Confined aquifer


What is an aquifer

what is anaquifer?

  • an aquifer is geologic media that can yield economically usable amounts of water.

Dirt and rocks

Depends on

who’s using it


What is an aquifer1

what is anaquifer?

Limestone (especially karstified),

sandstone, sand, gravel, fractured rocks

It must have spaces that water can fill up;

These spaces are called pores. We call these

Materials porous. (The related noun is porosity)

It is measured by volume of space/total volume of material.


What is an aquifer2

what is anaquifer?

For a layer to be a true aquifer, it must

Allow water to flow; if a layer lets water flow,

We say its permeable. (The related noun is

Permeability.)

This is how interconnected the pores are.


What is an aquitard

what is anaquitard?

  • Another characteristic of most aquifers is the presence of layers that don’t let water flow easily.

  • an aquitard is geologic media that can not yield economically usable amounts of water.


What is an aquitard1

what is anaquitard?

  • clay, shale, unfractured dense rocks

  • Note: can still transmit water, but s l o w l y


What is a confining layer

what is aconfining layer?

  • A confining layer is an aquitard that bounds an aquifer.


What is a vadose zone

what is a vadose zone?

  • The vadose zone is the unsaturated geologic media between the water table and the land surface.

  • Scientific side note: There is a saturated capillary zone between the vadose zone and the water table.


The vadose zone

the vadose zone


What is a water table

what is a water table?

  • A water table is where the aquifer meets the vadose (unsaturated) zone.

  • Scientific definition: surface on which the fluid pressure in the pores of a porous medium is exactly atmospheric.


The water table

the water table


What is recharge

what is recharge?

  • Recharge is water that infiltrates to the water table of an aquifer.


Recharge

recharge


What is a water level

what is a water level?

  • A water level is the level at which water rests (or would rest) in a well.


The water level

the water level


2 rules of groundwater flow

2 rules of groundwater flow

  • water flows downhill (to lower potential energy)

  • water flows uphill to money


Water flows downhill to lower potential energy

water flows downhill (to lower potential energy)


Aquifers 101

Groundwater Flowpaths


What is an unconfined aquifer

what is an unconfined aquifer?

  • An unconfined aquifer is an aquifer that is bounded by a confining layer at its bottom but not at its top.


An unconfined aquifer

an unconfined aquifer


What is a confined aquifer

what is a confined aquifer?

  • A confined aquifer is an aquifer that is bounded by confining layers at its bottom and top and where the water level rises above the top of the aquifer.

  • Scientific side note: This is also an artesian aquifer. “Artesian” does not require water to flow at land surface.


A confined aquifer

a confined aquifer


Confined or unconfined

confined or unconfined?


Confined or unconfined1

confined or unconfined?


Confined or unconfined2

confined or unconfined?


Aquifers 101

same aquifer: unconfined and confined


Aquifers 101

Major aquifers


Same location confined and unconfined aquifers

same location: confined and unconfined aquifers


Outline3

Outline

  • Yay for aquifers!

  • Definitions

  • Flow through an aquifer

  • Pumping an aquifer


Aquifers 101

Your aquifer

as a bathtub

Spring/

base

flow

Recharge

Aquifer

Pumping


Aquifers 101

cross-section - structure


Aquifers 101

Your aquifer

as a bathtub

Spring/

base

flow

Recharge

Aquifer

Pumping


Recharge1

recharge


Aquifers 101

Graphic from Playa Lakes Joint Venture


Aquifers 101

Your aquifer

as a bathtub

Spring/

base

flow

Recharge

Aquifer

Pumping


What is permeability hydraulic conductivity transmissivity

what is permeability? hydraulic conductivity ?transmissivity?

  • Terms that describe the ease with which water flows through geologic media.

  • Scientific side note: permeability is independent of fluid type; hydraulic conductivity is specific to water and relative to a unit area; and transmissivity is specific to water and relative to the thickness of the aquifer and a unit width.


Aquifers 101

Your aquifer

as a bathtub

Spring/

base

flow

Recharge

Aquifer

Pumping


Aquifers 101

Comal Springs


Aquifers 101

Attack of the

Killer

Salt Cedar!


Outline4

Outline

  • Yay for aquifers!

  • Definitions

  • Flow through an aquifer

  • Pumping an aquifer


Aquifers 101

Your aquifer

as a bathtub

Spring/

base

flow

Recharge

Aquifer

Pumping


2 rules of groundwater flow1

2 rules of groundwater flow

  • water flows downhill (to lower potential energy)

  • water flows uphill to money


Pumping a well unconfined

pumping a well: unconfined


Pumping a well confined

pumping a well: confined


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