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4.1. GROUNDWATER AND PALEOCLIMATE 155
4.1.2 A multi-tracer study of groundwater in reclamation areas south-west
of the Nile Delta, Egypt
Participating scientists Werner Aeschbach-Hertig, Hany El-Gamal, Kamal Dahab (MINUF), Rolf
Kipfer (ETHZ)
Abstract The origin and renewal rate of groundwater used for irrigation in Egypt was investigated
using a variety of isotope and tracer techniques ( 2 H, 18 O, 14 C, SF6, 3 H- 3 He, noble gases). The main
result is that the groundwater is recharged from the Nile river, albeit at a slow rate. Water younger
than 50 yr is found only in the vicinity of surface water features in the Nile Delta.
� � ���per mil�
20
0
-20
-40
-60
-80
GMWL
A
Paleowater
Pre-1969 Nile water
Precipitation
-12 -10 -8 -6 -4 -2 0 2 4
�
� 18
O [per mil]
Figure 4.2: Mixing trend lines in stable isotope data. Squares A, B, and C indicate endmembers, dots
represent precipitation data, and triangles represent data from the wells. The latter lie on mixing lines
(dashed) between regional paleogroundwater and Nile water from before and after the completion of
the Aswan High Dam in 1969. These data clearly show that the groundwater is mainly recharged
from the surface water, but at a slow rate, such that most of the water infiltrated before 1969.
Background Egypt develops new agricultural
areas outside the overpopulated Nile Delta and
Valley. Such so-called reclamation areas depend
almost exclusively on groundwater as water resource.
For the long-term sustainability of these
developments it is of central importance to understand
the processes and rates of recharge of the
groundwater resources.
Methods and results The transient environmental
tracers SF6 and 3 H- 3 He have been used
to date the shallow groundwater, whereas dating
of the old groundwater by 14 C is currently
in progress. Noble gases and stable isotopes have
been analysed to obtain information on the conditions
during recharge. The results of the SF6
and 3 H- 3 He dating show that only the wells that
are located within a few kilometers of the artificial
irrigation canals in the delta have young ages of
between 1 and 25 years, indicating direct recharge
by water derived from the river. At larger distance
from the surface water, the age of the groundwater
exceeds the detection limit of these methods
B
C
Recent
Nile
water
(30 - 50 yr). The 14 C-analyses will provide information
on the age of the groundwater in the
reclamation areas, some tens of kilometers apart
from the surface water. The stable isotope data
provide clear indications of the on origin and age
of the groundwater, due to the change (enrichment
by evaporation) of the isotopic signature of
the Nile water resulting from the construction of
the Aswan High Dam in 1969 (see figure). Only
groundwater samples from the vicinity of the river
lie close to the the recent Nile water composition.
Most of the data lie close to the former Nile composition
but not the local precipitation, indicating
paleo-recharge derived from the river.
Outlook/Future work The 14 C ages should
enable us to further constrain the renewal rate
of the groundwater and thus to contribute crucial
information for a sustainable management of this
resource. A publication is in preparation.
Main publication El-Gamal [2005]