7.1 Notes - Aquifers and Springs

7.1 Notes - Aquifers and Springs

by James Cram

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Aquifers/Groundwater​

An aquifer is an underground layer of permeable rock or sand that collects, holds, and conducts water.

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​Aquifers are an important source of water for humans, supplying about 60% of the water we use.

Open Ended

What does the word permeable mean?

​9 Major Aquifers

Most of the water pumped from aquifers goes to agriculture to irrigate food crops. Over 80% of the irrigation water used in Texas comes from one aquifer, the Ogallala, the largest aquifer in the United States.​

Multiple Choice

Which of the following is the largest Aquifer in the US?

• Pecos

• Ogallala

• Edwards

• Trinity

​9 Major Aquifers

1) Pecos Valley

​2) Seymour

​3) Gulf Coast

​4) Carrizo-Wilcox

​5) Hueco-Mesilla Bolsons

​6) Ogallala

​7) Edwards Trinity (Plateau)

​8) Edwards (Balcones Fault Zone)

​9) Trinity

Anatomy of an Aquifer​

A good aquifer has good porosity (small spaces between grains), and good permeability (connections between pores)

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​Water enters ground in the recharge zone

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Zone of saturation: all the spaces are filled with water (this is groundwater)

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The upper limit of this zone is the water table.

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Multiple Choice

Is the zone of saturation above or below the water table?

• Above

• Below

Open Ended

What is meant by the zone of saturation?

Anatomy of an Aquifer​

Water table is a reflection of the surface. 

 

Wetlands occur where water table is at the surface.

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Lakes, streams occur when land surface is below the water table.

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Open Ended

What is the difference between a gaining stream, losing stream, and a disconnected stream?

​Water Movement in Soil

The residence time of water in a groundwater aquifer can be from minutes to thousands of years.

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The Ogallala aquifer was formed about 2 to 6 million years ago. Groundwater can also be very new. Water that falls as rain and enters the Edwards aquifer near San Marcos can be found emerging from springs a few days or even hours later.​

​3 Types in Texas

Unconfined Aquifers

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​Confined Aquifers

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​Karst Aquifers

​Unconfined Aquifers

Directly connected to the surface and have water levels dependent on relatively constant recharge.

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Best known is Ogallala 

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As much as 95% of the recharge water in Texas comes from playa lakes. 

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​A playa lake is a naturally occurring wetland formed when rain fills small depressions in the prairie.

Multiple Choice

Directly connected to the surface and have water levels dependent on relatively constant recharge. What kind of aquifer is this?

• Unconfined Aquifers

• Confined Aquifers

• Karst Aquifers

​Confined Aquifer

Saturated layers of pervious rock bounded above and below by largely impervious rock

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A confined aquifer containing water under pressure is called an artesian aquifer

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Artesian pressure can be so great that if a well is drilled into the aquifer, groundwater can be pushed up all the way to the surface without the need for pumps.​

Multiple Choice

Saturated layers of pervious rock bounded above and below by largely impervious rock. What kind of aquifer is this?

• Unconfined Aquifer

• Confined Aquifer

• Karst Aquifer

​Karst Aquifers

​Found in limestone and marble rock which can be dissolved by water 

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Can form large holes, channels, and even large underground caverns, lakes and streams

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Edwards Aquifer is a confined karst aquifer flowing through limestone in Texas

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​There are 3 Karst Aquifers in Texas

Multiple Choice

What do we call a confined aquifer with water under pressure?

• Karst Aquifer

• Artesian Aquifer

​Springs

​The places aquifer water flows to the surface

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Springs can be cool water or so hot the water steams and almost boils when it reaches the surface

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Springs often form along faults

Multiple Choice

Which type of aquifer can form large holes, channels, and even large underground caverns, lakes and streams?

• Karst Aquifer

• Artesian Aquifer