Kein Folientitel

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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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Khartoum, Sudan
How much more groundwater can be pumped for the
drinking water supply ?
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1963/1964
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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 ?
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Cholistan
Area of hydrogeological reconnaissance 15,500
km2 habitants 300,000 heads
of animals 2,000,000 minimum
temperature -3C maximum
temperature 50C annual
precipitation rate lt200 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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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, Indonesia
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Drinking Water for Bandung

• Are the Lembang and Bandung Basins
  hydraulically connected ?
• How large is the vulnerability to pollute the
  fesh water resources ?

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Lembang water
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Conclusion

• 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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Potential of Isotope Hydrological Methods

• 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