institute for joint geoscientific research contribution of isotope techniques to water resources...

Institute forJoint Geoscientific Research

Contribution of Isotope Techniques to

Water Resources Assessment

Contribution of Isotope Techniques to

Water Resources Assessment

Mebus A. Geyh

5th IHP/IAHS George Kovacs Colloquium

UNESCO, Paris, 2 - 3 June 2000


IndonesiaSudan

Pakistan


Khartoum, SudanKhartoum, SudanKhartoum, SudanKhartoum, Sudan

How much more groundwater can be pumped for the drinking water supply ?


Blue N

ile

Khartoum

0 5 10 km

piezometric line

904704504

345

350

355

360365365

370

375

370

345350

1710

1710

360

360365

345

Nile


clay and mudstonesand and sandstone 0 2 4 km

400

300

200

100

0

m aslOMDURMAN

SW

Nile

NE

2.4 x 10-4 m/s 5.0 x 10-5 m/s

300 MCM/yr

19 mio m3/yr/50 km

precipitation: 60 - 300 mm/yr


1963/1964


3H

va

lue

(T

U)

75

100

discharge rate : q = v x h = 42 m/yr x 5 m = 210 m3/yr/m

hydraulic conductivity: K = v / grad = 42 m/yr x 1000/2 = 8 x 10-4 m/s

Darcy velocity : v = s x n / t = 5000 mx 0.1 / 12 a = 42 m/yr

expected < 2.4 x 10-4 m/s

0 1 2 3 4 50

25

50

distance from Nile river (km)


3 4 5210

0

1000

2000

3000

4000

5000

EC (S/cm)

upper aquifer zone

lower aquifer zone


3 4 5210distance from Nile river (km)

0

20

40

60

80

100

NO3- (mg/l)


3H

va

lue

(T

U)

75

100


hydraulic conductivity: K = v / grad = 42 m/yr x 1000/2 = 8 x 10-4 m/s

Darcy velocity : v = s x n / t = 5000 mx 0.1 / 12 a = 42 m/yr

expected < 2.4 x 10-4 m/s

0 1 2 3 4 50

25

50


3H

va l

ue

(TU

)Darcy velocity : v = s x n / t = 1500 m x 0.1 / 12 a = 13 m/yr


hydraulic conductivity : K = v / grad = 13 m/yr x 1000/2 = 2.1 x 10-4 m/s

= 42 m/yr

= 8.0 x 10-4 m/s

= 210 m3/yr/m


Blue N

ile

Khartoum

0 5 10 km

piezometric line

904704504

345

350

355

360365365

370

375

370

345350

1710

1710

360

360365

345

Nile

2500

6400

4900

50001540

1700 14C age yr

0

1650

17,600

-12‰ < 13C < -9‰


100

90

80

70

60

50

40

0 5 10 15 20 25 30

0 5 10 15 20 25 30distance from Nile river (km)

0

10

20

30

q (

m/a

)14

C a

ctiv

ity (

pM

C)

1000 BC

500 AD

1980 AD

1750 BC

240 BC

500 AD

1980 AD


numerical model : 21 mio m3/yr

isotope technique : 4 mio m3/yr

RECHARGE RATE (50 km Nile river)

WATER BALANCE (250 km) 1976 - 1986

Nile recharge - pumping:

+ 44 - 210 MCM = -166 MCM

groundwater table: = -7,8 m actual: ca -10,0 m


Conclusion

—Present-day groundwater recharge by the Nile river is about 20% of the pumping rate.

—Mainly fossil groundwater is pumped for the drinking water supply recharged some 4000 yr BP.

—The piezometric surface is mainly the relict of the palaeo-groundwater.


Thar Desert, Pakistan

Is fresh groundwater recharged ?

Thar Desert, Pakistan

Is fresh groundwater recharged ?


Cholistan

Area of hydrogeological reconnaissance 15,500 km2

habitants 300,000 heads of animals 2,000,000

minimum temperature -3°C maximum temperature +50°C

annual precipitation rate <200 mm/yr potential evaporation rate -2700 mm/yr


10.000 mio m3/yr fresh groundwater

in the Thar desert !

—How large was the groundwater recharge rate ?

—When was the fresh groundwater recharged ?

—How was the fresh groundwater recharged ?


-80

-60

-40

-20

0-2-4-6-8-10-12-14

Hindukushgroundwater 1900 m asl

Sutley River 1300 m asl

fossilgroundwater 1300 m asl

evaporation line

0

2H

(‰

)

18O (‰)


14,000 10,000 8000 6000 4000 2000 0

Indian lakes

conventional 14C age (yr BP)12,000

fre

qu

enc y

2

4

6

8 we

tdr

ycl

ima

te

Hamad

Cholistan

1

2

3

1

3

5

reservoircorrection

fre

qu

enc y

fre

qu

e nc y

-1300 yr

-3000 yr

dry period

dry period

dry period


0 5000 10000 1500014

C age BP

200

180

160

140

120

100

80

60

40

20

dept

h (

m b

g)

conventional TDIC 14

C agereservoir corrected

14C age

past:14

C 75 yr/m

5 mm/yr

present:3H <1mm/yr

Recharge Rate


Conclusion

—Recharge occurred between 16,000 to 4000 yr BP.

—Recharge rate was about 5 mm/yr in the past while that of today is around 1 mm/yr.

—Recharge occurred from innundations of the Old Hakra River.


Bandung, IndonesiaBandung, Indonesia


—Are the Lembang and Bandung Basins hydraulically connected ?

—How large is the vulnerability to pollute the fesh water resources ?

Drinking Water for Bandung


2000

1500

1000

500

m asl

Bandung Basin2000

1500

1000

500

Lembang Basin

well field

0 5 km

m asl

N S

impermeablebase rock

shallow groundwater fluvio-lacustrinesediments

volcanoclasticsediments

?


600

800

1000

1200

1400

1600

1800

2000

2200

2400

2600

-9,0 -8,5 -8,0 -7,5 -7,0 -6,5 -6,0‰)

altit

ude

(m a

sl)

springs

w ells

catchment

Lembang

18 = altitude effect ‰/100 m


-7,8-7,7-7,6-7,5-7,4-7,3-7,2-7,1-7,0

20 40 60 80 100

14C activity (pMC)

18O

(‰

)

Lembang water


23003200

35005500

10,000 14C age (yr BP)

0.3 x 10-7 m3/yr1.0 x 10-7 m3/yr

1.0 x 10 -7 m 3/yrLembang Basin

94%

43%

60%

59%0%

17%

0

0

750 m as

l

700 m asl

900

Bandung Basin

fault

0 5 km


ConclusionConclusion

— More than 30% of the pumped water is recharged in the Lembang Basin.

— The residence time of the pumped groundwater ranges from 1000 to 10,000 yr.


—Geohydraulic parameters• aquifer architecture• hydraulic conductivity• paleohydrological situation

—Water components of the hydrological cycle• origin of water components• sources of and vulnerability to pollution

—Groundwater movement and mass transport• pathways, recharge and discharge areas• transit and residence times / water balance• estimation of recharge and discharge rates• interconnection of surface water and groundwater• mixing processes and ratios (e.g. salinization)• tracing overexploitation and re-use of waste water

Potential of Isotope Hydrological Methods Potential of Isotope Hydrological Methods

institute for joint geoscientific research contribution of isotope techniques to water resources...

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