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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. Khartoum, Sudan.
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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
Khartoum, Sudan How much more groundwater can be pumped for the drinking water supply ?
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 ?
Cholistan Area of hydrogeological reconnaissance 15,500 km2 habitants300,000 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/yrfresh groundwater in the Thar desert ! • How largewas the groundwater recharge rate ? • When was the fresh groundwater recharged ? • Howwas the fresh groundwater recharged ?
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.
Drinking Water for Bandung • Are the Lembang and Bandung Basins hydraulicallyconnected ? • How large is the vulnerability to pollutethe fesh water resources ?
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.
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