GEOS 4430 Lecture Notes:Introduction to Hydrogeology

Dr. T. Brikowski

Fall 2012

file:introduction.tex,v (v. 1.43), printed August 28, 2012

Introduction

See NBC “Thirsty Planet” series, e.g.

American West

1

Why Study Hydrogeology?Population growth and global warming will lead to severe

freshwater shortages in the near future.

• U.S.

– West: Emphasis on groundwater.

∗ Water is a crucial problem west of 100o W longitude [the

east side of the Texas panhandle, J. W. Powell, 1875,

quoted in Stegner, 1954].

∗ average U.S. precipitation shows distinct drop-off west

of 100o (Fig. 1)

∗ Situation best summarized by Mark Twain (apocryphal):

“[In the West] whiskey is for drinking, water is forfighting over . . . ”1

1http://www.twainquotes.com/WaterWhiskey.html2

– East: emphasis on surface water management (rivers,

lakes, etc.) and drainage, contamination remediation, and

sea water intrusion. Also seawater intrusion.

• World:

– world wide water stress (pg. 61) increasing rapidly, causing

much suffering and potential war. See also decadal

summary

– Upper-vs-lower basin water usage

∗ similar to western U.S.Colorado River (p. 33) issues. See

also USBR Colo. R. sustainability study

∗ Euphrates River (Fig. 3): Turkey vs. Syria and Iraq.

Drying of Iraq marshes.

∗ Nile River basin (Fig. 4). Egypt vs. Sudan and Ethiopia.

See Nile Basin Initiative3

– Declining snowpack: primarily Himalaya, which supplies

much of India and south Asia (Fig. 5)

4

U.S. Precipitation 2009

Figure 1: Total precipitation, U.S., 2003. Note large dropoff

west of the Texas panhandle. After NOAA.

5

World Freshwater Stress

Figure 2: Observed and projected world freshwater stress (fraction

produced vs. available). After UNEP, updated at World Economic Forum

2009.

6

Euphrates River Basin

Figure 3: Euphrates river basin. After WorthNews. See also

satellite photos, NPR 2009 of Ataturk Reservoir, Turkey.

7

Nile River Basin

Figure 4: Nile river basin elevation and hydrology. After

WaterWatch.8

Himalayan Snowpack Decline

Figure 5: Changes in extent of glaciers in the Western Himalaya

[Fig. 1, Prasad and Singh, 2007]. See more immediate problem

in Peru.9

Texas 2011 Drought

• worst single-year drought in Texas history

• Drought Monitor, also seasonal drought outlook

• severe impacts, e.g. Amarillo water supply, Lake Meredith

currently “empty” (official dead pool elev is 2850 ft, 2011

record low of 2842.5 ft, depth 28.5 ft)

• North Dallas (NTWMD) in persistent Stage II water

restrictions

• very unusual conditions (see TX State Climatologist blog,

continues trend of high-T departure from historical trends

10

U.S. Trouble Spots

• Western Colorado River

– about 35 million people depend on this river for drinking

water

– since 2002 demand has exceeded supply by 10% (see Fig.

1, USBR Basin Status Report

– 11 year drought has greatly depleted storage in the system

(e.g. Lake Mead, Fig. 6)

– fortunately, per-capita water use has declined significantly

(Figs. 6-7) in that basin, meaning conservation can help a

lot

11

Climate Change and Drought

• see Global Change Impacts in the United States, [USGCRP,

2009]

• Warming predictions:

– U.S. average temperature has risen by 1.1◦C in the past

50 years

– expect additional 5-6◦C warming by 2100 at current CO2

emissions rates [p. 29, USGCRP, 2009]

– greatest warming in mid-continent, especially west (

[Colorado River headwaters, p. 29 USGCRP, 2009]

(compare to 1940-2005 observed trends

– optimistic models of reduced emissions predict 3-4◦Cwarming

12

– will result in over half the year with days warmer than

90◦F by 2100 in North Texas [p. 34, USGCRP, 2009]

– around 120 days over 100◦F for North Texas by 2100 [p.

90, USGCRP, 2009]

• only mild changes in precipitation predicted [p. 30-31,

USGCRP, 2009]

• warming will lead to increased evapotranspiration by plants,

leading to significant water stress in part of U.S. and mid-

latitudes worldwide (Fig. 8)

• Get ready for a wild ride! E.g. Australian example

– 12 year drought began around 2000, part of a general

southern hemisphere drought13

– forced steep decline in rice production, leading to global

shortages and conversion to wind production

– some reservoirs dropped to 12% of normal (compare to

Lake Lavon, where at 35% of normal Stage 4 Emergency

restrictions apply, no outdoor use of water)

– drought ended 2010 with heavy rains, reservoirs rising, now

at 35% of capacity

– Australian electorate now becoming quite serious about

climate change

– drought has resumed along west coast (Perth)

14

Lake Mead, NV

1060

1080

1100

1120

1140

1160

1180

1200

1220

1240

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

2005

2010W

ater

Ele

vatio

n (f

t)

Lake Mead, NV Monthly Water Elevation

Drought

Average

Maximum

Critical Shortage

Figure 6: Lake Mead, NV monthly water levels 1937-present. Current levels approaching those experienced in shorter

severe droughts 1955 and 1965. Mandatory rationing below shortage line, AZ handles 94% of the rationing, NV the rest. Mead

supplies 90% of LV water.

15

Las Vegas City Water Intake Tunnel

Figure 7: Las Vegas-Lake Mead water intake tunnel plan. One of two current intakes is at 1,050 ft elev, and may soon

be above water. From TunnelTalk.

16

Warming-Related Water Stress

Figure 8: Warming will greatly affect water availability by 2100; IPCC4

[2007] lower emissions scenario (SRESa1b) mean results.

17

Unique U.S. Water Stresses

• hydrofracing uses considerable water

• 2012 drought is bringing pressure to recycle that water or

halt this use

• others such as beverage industries have recognized that water

access is their most persistent future business risk factor

• i.e. hydrology is important even to oil and other geologists

18

Water Trends

19

Water Sources

• average water usage in U.S. is ∼ 30% groundwater (Fig. 9)

• U.S. water usage trends:

– Consumptive water use up steadily

– ratio of groundwater to surface water also generally

up, partly due to climate (recent droughts ⇒ increased

groundwater extraction)

– since ∼1980 water use down slightly, but

ground/surface water ratio increasing (Fig. 9)

• U.S. Climate trends

– long term climate predictions are for significant heating,

little precipitation change20

– historical trends show notable warming in the West (1◦F /decade) since 1970, and increase in precipitation

21

Total Water Usage in the U.S., 1950-2005

Figure 9: Total water usage by source in the U.S., 1950-2005.

Groundwater use is steadily increasing, total and surface water

use has leveled off. See USGS, and [Hutson et al., 2004].

22

U.S. Water Usage by Category, 1950-2005

Figure 10: Total water usage by category in the U.S., 1950-2005.

Approximately 30% of thermoelectric water was saline (TDS above drinking

water standard of 1000 mg/l), 2.5% of the thermoelectric total was

consumptive use (not returned to surface or groundwater streams).23

Water Usage

• average groundwater usage in western U.S. is much higher

• average groundwater usage in Texas 60%, and generally

increasing with time (Fig. 11)

• largest users in west are agricultural irrigation, but this is

declining, partly in favor of municipal use (Fig. 12)

• 94% of NTX use is surface water. Current status of N. Texas

reservoirs or NOAA

24

Sources of Consumed Water, Texas, 1974-1993

Figure 11: Sources of consumed water, Texas, 1974-1993.

Texas Water Resources Planning Commision.

25

TX Water Use Categories 1974, 1993 & 2008

Figure 12: Water usage categories, Texas, 1974 (left), 1993 (middle) and

2008 (right). Municipal usage (blue in right two figures, green on left) has

grown from 12% in 1974 to 22% in 1993 to 25% in 2002. Concomitantly

irrigation usage has declined from 78% to 68% to 62% respectively. Texas

Water Resources Planning Commission and TWDB.

26

Projected Water Usage by Category, Texas

Figure 13: Projected water usage by categories, Texas. From

Texas Water Plan 2002. Municipal usage will increase more

rapidly than decrease in irrigation.

27

City Water Usage, Texas, 2006

RIC

HA

RD

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N

La

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eg

as,

NV

PL

AN

O

MID

LA

ND

AM

AR

ILL

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son,

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US

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100

120

140

160

180

200

220

240

260

280

Per-Capita Water Use 2006

Ga

llons

/Ca

pit

a/D

ay

(GP

CD

)

Figure 14: 2006 Estimated water usage for Texas cities with population

greater than 95,000. Richardson has the greatest usage, nearly double that

of San Antonio, and higher than Las Vegas. Data from TWDB, see also

Texas Comptroller.28

Projected Groundwater Supply, Texas

Figure 15: Projected groundwater availability, Texas major

aquifers. From Texas Water Plan 2002. See aquifer map for

locations.

29

High Plains Aquifer Lifetime

MidlandOdessa

Lubbock

Amarillo40

27

20

New

Mex

ico

Texa

s

Ok l ahoma

Texas

P r a i r i e D o g T o w n F o r k R e d R i v e r

C a n a d i a n R i v e r

Co l o r a d o R i v e r

B r a z o s R i v e r

GLASSCOCKMIDLANDECTOR

HOWARDMARTINANDREWS

BORDENDAWSONGAINES

GARZALYNNTERRYYOAKUM

DICKENSCROSBYLUBBOCKHOCKLEYCOCHRAN

MOTLEYFLOYDHALELAMBBAILEY

BRISCOESWISHERCASTROPARMER

DONLEYARMSTRONGRANDALLDEAFSMITH

WHEELERGRAYCARSONPOTTEROLDHAM

HEMPHILLROBERTSHUTCHINSONMOOREHARTLEY

LIPSCOMBOCHILTREEHANSFORDSHERMANDALLAM

Estimated UsableAquifer Lifetime

Estimated UsableAquifer Lifetime

0 10 20 30 40 505

Miles

Perennial StreamInterstateMajor RoadCounty BoundaryOgallala Aquifer ExtentOutside of TexasLand Surface Over the Ogallala Aquifer in West Texas

Less than 15 years16 to 30 years31 to 50 years51 to 75 years76 to 100 yearsGreater than 100 years

Water Table Rising

No Saturated Thickness Changebetween 1990 and 2004

Already Below 30 feet

Figure 16: Projections for usable lifetime of Ogallalla Aquifer,

Texas Panhandle. From TTU.

30

India Groundwater Declines

Figure 17: India annual pumping as fraction of recharge. From

NASA.

31

California Snowpack Reduction

Figure 18: Projected climate-change-related changes to California

snowpack. From Climate Change and Water Resources Factsheet. Lake

Lavon can hold 275,000 acre-ft of water. See 2007-2009 summary , note

2008 La Nina event. Also interactive prediction maps.32

What Hydrologists Do

• primarily addressed water supply issues until 1970’s (i.e.

finding water)

• emphasis on contamination issues since creation of EPA

– requires a much more quantitative approach

– typically involving governmental regulations and/or lawyers

– current emphasis on “doing nothing”: finding and

preserving uncontaminated water supplies, establishing

natural attenuation as the typical remediation approach

– also Brownfields (development of contaminated properties,

e.g. American Airlines Center’)

• now returning to water supply issues given the problems of

drought, global warming and full allocation of resources33

• see also USGS Hydrology Primer (last updated 2010)

34

Definitions

35

Definitions

• Ground Water: two overlapping definitions

– subsurface water that occurs beneath the water table in

porous geologic formations that are fully saturated

– that portion of subsurface water that can be collected with

wells, drainage pipes etc., or that flow naturally to the

surface via springs and seeps (NOTE: not all subsurface

water is groundwater)

– important to remember there is accessible and inaccessible

water in the subsurface

36

Definitions (cont.)

• Ground Water Hydrology: the study of the origin,

distribution, movement and physical/chemical properties of

ground water. A subset of hydrology, the study of all

terrestrial waters.

• Surface Water Hydrology: the study of subaerial waters

(in contact with the atmosphere), excluding oceans. Civil

engineers usually mean “lakes and bays”, geologists usually

mean “rivers and streams” when using this term.

• Hydrogeology: emphasizes the hydrologic aspects of geology,

e.g. lithologic or facies influences on groundwater movement

• Geohydrology: emphasizing geologic aspects of hydrology,37

particularly the effects of the porous medium through which

groundwater flows.

• in principle Hydrogeology and Geohydrology have different

meanings, in common usage they are identical

• Hydrosphere: that region of the Earth occupied by water,

including lakes, rivers, oceans, subsurface water, glaciers,

+/- atmospheric water (clouds, vapor, precipitation)

38

The Hydrologic Cycle

39

Definitions: Hydrologic Cycle

• the hydrologic cycle refers to the global chemical balance of

H2O in the hydrosphere (Fig. 19)

• start with Precipitation - form is important, e.g. in Nevada

snow is generally biggest contributor to groundwater

• some part of precipitation onto the ground becomes surface

runoff or overland flow

• the rest is infiltration: driven by gravity and pressure,

Ppore ≤ Patmosphere

• much infiltrated water goes back out to the atmosphere by40

evaporation or transpiration (uptake by plants and release

to atmosphere)

• infiltration that makes it to the water table becomes

groundwater, and is termed recharge

• while infiltrated water is above the water table, it forms an

unsaturated (or vadose) zone where pores are filled with a

mixture of air and water. Pore pressure is negative in this

zone.

• groundwater in the saturated zone is found in aquifers (rocks

through which water travels most easily). These are generally

separated by aquitards (water travels slowly through these)

or aquicludes (“impermeable” zones or layers)41

• within the aquifer, water occupies the accessible pore space in

the rock (some pores may be blocked off, or “permanently”

occupied by something else. The accessible space is referred

to as the effective porosity

• groundwater that discharges into a stream is termed baseflow(total flow in the stream is runoff)

42

Quantified Hydrologic Cycle

Figure 19: An illustration of the hydrologic cycle. After online

textbook. See flux estimates (p. 5) for water balance.

43

Water Balance

• much of hydrology is based on determining the water balance

for all or some part of the hydrosphere (e.g. a groundwater

basin)

• water balance is just a mass balance:{rate of

mass in

}−

{rate of

mass out

}=

{change in

content

}

44

Groundwater Basics

Some good online resources are now

available to provide overviews of hydrology.

My current favorite is the USGS Basic ground-

water hydrology publication [Heath, 1987].

The classic textbook Freeze and Cherry [1979]

is now quite old, but is one of the few calculus-

based geologic hydrology texts (much more

readable than civil engineering texts).

45

Aquifer Types

See also Fig. 20:

• confining layer (aquiclude): low-permeability bed or unit

• confined aquifer: an aquifer overlain by a confining layer

• unconfined aquifer (phreatic or water table): water table lies

below the top of the aquifer

• semi-confined: an aquifer exhibiting confined and unconfined

behavior at different locations (e.g. a sand layer in an alluvial

fan)46

• artesian: can simply mean confined, in common usage it

means an aquifer from which water will flow upward to the

surface given an appropriate conduit (e.g. a borehole)

• perched: a saturated zone lying above unsaturated rock

47

Aquifer Features

Figure 20: Important features of groundwater systems,

including aquifer/aquitard, water table, etc. After Heath

[1987].48

Water Table Definitions

• the undulating plane below the ground surface at which pore

water pressure is equal to atmospheric

• also the dividing line between the unsaturated and saturated

zones

• Phreatic surface: the level to which water will rise in a well

open only within the aquifer

– different than the water table only for confined aquifers

– when phreatic surface lies at or above the ground surface,

an artesian well or spring is possible

49

Motivating Examples

50

Southwest Drought 1998-2010

• 12-year drought (as of 2010) longest in historical record

[Overpeck and Udall, 2010]

• consistent with pre-historic extreme droughts [USGCRP,

2009, p. 130]

• longer and more frequent droughts predicted by climate

change models, would reduce supply to less than current

demand within the decade [Barnett and Pierce, 2008]

• i.e. permanent water shortage in most of the Southwest

51

Gulf of Mexico Dead Zone

The most severe nutrient pollution issue in U.S. is Gulf Coast

“Dead Zone”, with Chesapeake Bay a close second.

• high nutrient loads in Mississippi River discharge lead to large

algal blooms [CENR, 2000, p. 13]

• seasonal stratification leads to hypoxia zone, killing marine

life, e.g. Baltic Sea image

• see summary of nutrient source spatial and temporal

distribution [CENR, 2000, p. 27, 29], also USGS streamflow

& nutrient delivery to Gulf of Mexico

• see LSU Current Status webpage52

• expanding steadily with time (2010 is largest ever measured,

area the size of New Jersey)

53

Other Resources

54

Useful Links

This is intended to be an ever-evolving list of useful links on

the general topic of this note set.

• groundwater extraction is 40% of sea level rise [Pokhrel et al.,

2012]

55

Bibliography

56

Tim P. Barnett and David W. Pierce. When will Lake Mead go dry? Water Resour. Res., 44(W03201), 29 March 2008. doi: 10.1029/2007WR006704. URL http://www.agu.org/journals/pip/wr/2007WR006704-pip.pdf.

CENR. Integrated Assessment of Hypoxia in the Northern Gulf of Mexico. Report, NationalScience and Technology Council Committee on Environment and Natural Resources,Washington, D.C., May 2000. URL http://oceanservice.noaa.gov/products/hypox_finalfront.pdf.

R. A. Freeze and J. A. Cherry. Groundwater. Prentice-Hall, Englewood Cliffs, NJ, 1979.

R. C. Heath. Basic ground-water hydrology. Water Supply Paper 2220, U.S. Geol. Survey,Denver, CO, 1987. URL http://water.usgs.gov/pubs/wsp/wsp2220/.

S. S. Hutson, N. L. Barber, J. F. Kenny, K. S. Linsey, D. S. Lumia, and M. A. Maupin. Estimateduse of water in the united states in 2000. Circular 1268, U. S. Geol. Survey, Reston, VA,May 2004. URL http://water.usgs.gov/pubs/circ/2004/circ1268/.

IPCC4. Climate Change 2007: The Physical Science Basis, Summary for Policymakers (4thClimate Assessment Report). Technical report, U.N. Intergov. Panel on Climate Change, 5February 2007. URL http://www.ipcc.ch/SPM2feb07.pdf. 18 pp.

Jonathan Overpeck and Bradley Udall. Dry times ahead. Science, 328(5986):1642–1643, 2010.doi: 10.1126/science.1186591. URL http://www.sciencemag.org.

Yadu N. Pokhrel, Naota Hanasaki, Pat J-F Yeh, Tomohito J. Yamada, Shinjiro Kanae, and TaikanOki. Model estimates of sea-level change due to anthropogenic impacts on terrestrial waterstorage. Nature Geosci, advance online publication, May 2012. ISSN 1752-0908. doi:10.1038/ngeo1476. URL http://dx.doi.org/10.1038/ngeo1476.

A. K. Prasad and R. P. Singh. Changes in Himalayan Snow and Glacier Cover Between 1972and 2000. EOS, 88(33):326, 17 August 2007. doi: 10.1029/2007EO330002.

W. E. Stegner. Beyond the Hundredth Meridian: John Wesley Powell and the Second Openingof the West. Houghton Mifflin, Boston, 1954.

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USGCRP. Global Climate Change Impacts in the United States. CambridgeUniversity Press, 2009. URL http://www.globalchange.gov/publications/reports/scientific-assessments/us-impacts. Quadrennial report to U.S. Congress.

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