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UP: Umweltphysik

UP 1: Hydrosph
äre

UP 1.6: Fachvortrag

Montag, 13. März 2006, 15:30–15:45, A

Environmental tracer study of groundwater recharge near the Nile Delta, Egypt — •Werner Aeschbach-Hertig¹, Hany El-Gamal¹, Kamal Dahab², Rolf Kipfer³, and Georges Bonani⁴ — ¹Institute of Environmental Physics, University of Heidelberg — ²Geology Department, Faculty of Science, Minufiya University, Egypt — ³Isotope geology, ETH Zürich — ⁴AMS Radiocarbon Lab, ETH Zürich

We investigated groundwater in so-called reclamation areas near the southwestern Nile Delta. Since these areas depend almost exclusively on groundwater, it is important to understand the origin and rate of groundwater recharge. Several environmental tracer methods (CFCs, SF₆, ³H-³He, ¹⁴C) were used to date the groundwater, whereas noble gases and stable isotopes were applied to study its origin. The stable isotopes clearly show that the groundwater is derived from the Nile river. The change of the river’s isotopic composition in response to the construction of the Aswan High Dam allows us to distinguish between groundwater that infiltrated before and after 1969. Only wells close to surface water features reflect the modern Nile water composition. These wells are also the only ones that have young SF₆ and ³H-³He ages of up to 25 years. Further away from the surface water, ¹⁴C data indicate ages up to a few thousand years. In summary, the data show that the regional aquifers are recharged from the surface water, albeit at a rather low rate.