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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. - PowerPoint PPT Presentation
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The water cycle is not as simple as this as youve read about in the peer reviewed article. We spent the beginning of the school year looking at how water in the oceans evaporates and condenses to form clouds along with the energy exchanges involved in those phase changes. In this unit, we will focus on precipitation and where the water is stored and surface runoff. This is the basis for the field trip next week. 1

Aquifers 101 Robert E. MaceTexas Water Development BoardGroundwater 101November 10, 2010OutlineYay for aquifers!DefinitionsFlow through an aquiferPumping an aquifer

World Water Balance

From Freeze and Cherry (1979)4groundwater and Texas~60 percent of the 16.6 million acre-feet of water used~80 percent of groundwater is used for irrigationgroundwater provides 39 percent of water to citiestastes good when yer thirstyExamples of AquifersThe following slides are examples of aquifersAs we discuss them, try to think of how you would define AQUIFER

catfish farm wellEdwards aquifer

flowing well at 40,000 gpm 1/4 of San Antonios use 9% of Annual Recharge worlds largest artesian well

National Geographic (1993)7Used to run a catfish farm, closed due to fecal coliform, not overuseDoes Darcys Law apply? How high can permeability be?

In this aquifer 15% of well tests have no measurable drawdown (called zero drawdown wells)

Supplies San AntonioRiverwalkSchlitterbahn

Major aquifers

Minor aquifers

Hickory Aquifer, sandstone11Hickory Aquifer, Llano uplift area, near Honey Creek (HW 71)

Edwards-Trinity (Plateau) Aquifer, limestone 12Edwards-Trinity Plateau Aquifer (Fort Terrett Mbr), Interstate 10 near Kerrville

Ogallala Aquifer, sand and gravel13Ogallala Aquifer near the entrance to Palo Duro Canyon State Parkan aquifer is geologic media that can yield economically usable amounts of water. Fill in the definition in your noteswhat is an aquifer?Dirt and rocksDepends onwhos using it14Aquifers have certain properties:

Limestone (especially karstified), sandstone, sand, gravel, fractured rocks

It must have spaces that water can fill up; These spaces are called pores. We call theseMaterials porous. (The related noun is porosity)It is measured by volume of space/total volume of material.15Porosity is determined by:1. Shape - Well rounded particles have greater porosity than angular.ROUNDANGULARPorosity - The amount of space in between sediments.POROSITYROUNDNESS2. PACKING- The more closely packed the particles the lower the porosity.UNPACKEDPACKEDPOROSITYPACKING3. SORTING- - If all particles are the same size they are sorted. - If the particles are different sizes they are unsorted (poorly sorted) - The more sorted the higher the porosityPOROSITYSORTING

what is an aquifer?For a layer to be a true aquifer, it mustAllow water to flow; if a layer lets water flow,We say its permeable. (The related noun isPermeability.)

This is how interconnected the pores are.PermeabilityAbility of water to pass throughAffected by: packing and particle sizeTighter packing and Smaller particles = less permeabilityLooser Packing and Larger particles = more permeabilityPERMEABILITYPARTICLE SIZEOther things about PermeabilityPermeability Rate How fast a fluid can flow through a materialImpermeability (not permeable) is due to:A. Tightly packing of particlesB. Cementing of particles by clayC. Cementing of particles by ice

GRAVELRapid drainageFINE SANDModerate drainageCLAYSlow drainagePERMEABILITYClay is impermeable water will not flow through easilyAnother characteristic of most aquifers is the presence of layers that dont let water flow easily.an aquitard is geologic media that can not yield economically usable amounts of water.

what is an aquitard?

24clay, shale, unfractured dense rocksNote: can still transmit water, but s l o w l ywhat is an aquitard?

25A confining layer is an aquitard that bounds an aquifer.

what is a confining layer?

26Geologic layers in loveThe 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.what is a vadose zone?

27the vadose zone

28A 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.what is a water table?

29the water table

30Capillary zoneRecharge is water that infiltrates to the water table of an aquifer.what is recharge?

31recharge

32A water level is the level at which water rests (or would rest) in a well.what is a water level?

33the water level

34DipstickAlso tells which way water may be goingwater flows downhill (to lower potential energy)

water flows uphill to money

2 rules of groundwater flow35water flows downhill (to lower potential energy)

Groundwater Flowpaths

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

38an unconfined aquifer

39A 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.what is a confined aquifer?

40a confined aquifer

41Menage a tuaconfined or unconfined?

42Menage a tuaconfined or unconfined?

43Menage a tuaconfined or unconfined?

44Menage a twasame aquifer: unconfined and confined

45Which way is the water flowing?

Major aquiferssame location: confined and unconfined aquifers

47OutlineYay for aquifers!DefinitionsFlow through an aquiferPumping an aquifer

Recharge

Aquifer

Pumping

Spring/baseflowYour aquiferas a bathtub49Mention availability: recharge and storage in the tubParadox of availability

50- controls:precipitationrunoffevapotranspirationinfiltrationtransmissivity (explain)streams, rivers, springsevapotranspirationpumpingcross-formational flow

cross-section - structure51When I say structure, what I mean is where the aquifer is underground. Structure is critical for modelingExplain figureMany minor aquifers do not have good structure.

Recharge

Aquifer

Pumping

Spring/baseflowYour aquiferas a bathtub52recharge

53

Graphic from Playa Lakes Joint VentureAttack of theKillerSalt Cedar!

56

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