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
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IndonesiaSudan
Pakistan
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Khartoum, SudanKhartoum, SudanKhartoum, SudanKhartoum, Sudan
How much more groundwater can be pumped for the drinking water supply ?
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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
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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
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1963/1964
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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)
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3 4 5210
0
1000
2000
3000
4000
5000
EC (S/cm)
upper aquifer zone
lower aquifer zone
distance from Nile river (km)
3 4 5210distance from Nile river (km)
0
20
40
60
80
100
NO3- (mg/l)
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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)
3H
va l
ue
(TU
)Darcy velocity : v = s x n / t = 1500 m x 0.1 / 12 a = 13 m/yr
discharge rate : q = v x h = 13 m/yr x 5 m = 65 m3/yr/m
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
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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‰
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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
distance from Nile river (km)
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
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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.
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Thar Desert, Pakistan
Is fresh groundwater recharged ?
Thar Desert, Pakistan
Is fresh groundwater recharged ?
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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
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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 ?
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-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 (‰)
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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
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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
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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.
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Bandung, IndonesiaBandung, Indonesia
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—Are the Lembang and Bandung Basins hydraulically connected ?
—How large is the vulnerability to pollute the fesh water resources ?
Drinking Water for Bandung
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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
?
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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
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-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
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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
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ConclusionConclusion
— More than 30% of the pumped water is recharged in the Lembang Basin.
— The residence time of the pumped ground- water ranges from 1000 to 10,000 yr.
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—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
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