1

Subsidence & Groundwater Withdrawal

Flooding due to Subsidence

2

Houston-Galveston

Galveston Bay near Goose Creek

Greens Bayou flooded in 1989

3

Houston Ship Channel

This photograph takenabout 1926 shows a‘fault fissure’ in Pelley,one-half mile north ofthe oil fields. To theleft of the fault, theground had droppedabout 16 inches.

4

Baytown in 1960

5

Brownwood Subdivision

Wetlands Loss due to Subsidence

Drowned Coastal Woodlands

6

Subsidence activates faults

7

Impact of Subsidence

Structural Damage Observed at Former Woodlawn High School

Main Crack Main Crack

Secondary Crack Secondary Crack

Offset between sides of aperture is approximately ½ - 1 inch.

8

Laser Level Measurements Inside Western Band Room Wall

Surface extent of Louisiana’s aquifers and aquifer systems

GROUND-WATER WITHDRAWALS IN LOUISIANA, 1960-2000

15251438

1764

1341 1299

16341562

11731029

0

200

400

600

800

1000

1200

1400

1600

1800

2000

1960 1965 1970 1975 1980 1985 1990 1995 2000

WIT

HD

RA

WA

LS

, IN

MIL

LIO

N G

AL

LO

NS

PE

R D

AY

9

G R O UN D- WATER WITHDR AWALS , 2 0 0 0( 1, 6 0 0 MILL IO N G ALLO NS P ER D AY )

P u b lic S u p p ly2 2 %

In d u st r y17 %

P o w e r G e n e r a t io n2 %

R u r a l D o me st ic3 %

L ive st o c k0 %

Ir r ig a t io n4 8 %

A q u a c u l t u r e8 %

PUMPAGE BY MAJOR AQUIFER OR AQUIFER SYSTEM, 2000

354

8

798

291

22 423 7

6815 521

0

100

200

300

400

500

600

700

800

900

Red R

iver A

lluvia

l

Miss

issip

pi Rive

r Allu

vial

Upland

Ter

race

Chicot

South

ern H

ills

Evang

eline

Jasp

er

Cataho

ula

Cockfi

eld

Sparta

Carriz

o-W

ilcox

othe

r

WIT

HD

RA

WA

L R

AT

E,

IN M

ILL

ION

GA

LL

ON

S P

ER

DA

Y

1

1

AREAS WHERE WATERLEVELS IN ONE OR MOREAQUIFERS ARE DECLINING1 FOOT OR MORE PERYEAR BASED ON TRENDSOBSERVED AT DOTD/USGS NETWORK WELLS

10

0

0 KILOMETERS50

MILES50

Southern Hills aquifer system

BATON ROUGE FAULT ZONE(Approximate southern limit of aquifer system)

11

WITHDRAWALS FROM THE SOUTHERN HILLS AQUIFER SYSTEM, 2000(290 MILLION GALLONS PER DAY)

Public supply49%

Industry39%

Power generation5%

Rural domestic6%

All other uses1%

Artesian Well

Baton Rouge in 1943?

12

100

80

60

40

20

0

-20

Date

EB-168 (1500 ft)

EB-90 (2000 ft)

1940 1950 1960 1970 1980 1990 2000 2010

EB-128 (800 ft)

WBR-5 (1200 ft)

Clay

Sand

Limestone

Sandstone

Siltstone

Salt

Shale

Fractured Rock

Unfractured Rock

-21 -20 -19 -18 -17 -16 -15 -14 -13 -12 -11 -10

Log Permeability, m2

13

0.8

0.6

0.4

0.2

0

1940 1950 1960 1970 1980 1990 2000 2010Date

800-1200

1200-1500

1500-20002000-2400

Total

14

1900-1965 1935-1965 1964-1969 1964-1976 1975-1979 1981-1990 1991-2000 2001-20100

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

Time Interval

This Study

Releveling/Extensometers

WITHDRAWALS FROM THE CHICOT AQUIFER SYSTEM, 2000(800 MILLION GALLONS PER DAY)

Public supply11%

Industry9%

Power generation2%

Other uses2%

Irrigation68%

Aquaculture8%

15

Water levels show long-term declines and seasonal fluctuations at 2 wells screened in the Chicot aquifer system in southwestern Louisiana, 1940-2000.

1940 1950 1960 1970 1980 1990 2000

One Year Seasonal CycleDrainage of Confining Layer

16

One Year Seasonal CycleBottom Half of Confining Layer

Second Seasonal Cycle Drainage of Confining Layer

Second Seasonal Cycle Bottom Half of Confining Layer

17

Fifth Seasonal Cycle Drainage of Confining Layer

Fifth Seasonal Cycle Bottom Half of Confining Layer

Five Seasonal CyclesDrainage at Low Water Level

18

Five Seasonal CyclesDrainage at Low Water Level

10

9

8

7

6

5

4

3

2

1

0

0 20 40 60 80 100

Maximum Decline in Water Level, meters

SJV

SCV

HGTEPALVNNOL

SG

BRL

19

CONCLUSIONS

• Declining water levels in the Chicot and Southern Hills Aquifers should drain intervening clay layers and produce significant compaction and land surface subsidence

• The amount and temporal distribution of subsidence will depend on the number and thickness of clay layers which varies both North to South and East to West

20

CONCLUSIONS

• Drainage and compaction of confining layers also can result from seasonal variations in water levels even if long term water levels do not change

• Land surface subsidence will continue in the region even if water levels remain constant.

• The potential for future land surface subsidence in the region is high.

Figure 13.13

Fissures and depressionsFissures and depressionscaused by caused by

ground subsidence ground subsidence due to due to overpumpingoverpumping

of groundwaterof groundwater

21

St. Mark’s Square, Venice

p. 254

p. 255