Africa Water Atlas - UNEP/GRID-Sioux Falls

conditions (Gossel and others 2004, CEDARE 2001,
Ebraheem and others 2003). Experts generally
accept that the system has not been in equilibrium
for thousands of years and that groundwater levels
were already declining well before artificial extraction
began (Heinl and Brinkman 1989, Gossel and others
2004). Thus, any water withdrawal from the aquifer
under the current climate would be considered
“water mining,” or a rate that exceeds recharge.
Precipitation
Figure 2.16.2: Water abstraction by population (Source:
CEDARE 2001)
of groundwater decline will significantly exceed
historical rates (Ebraheem and others 2003).
While it is clear that the aquifer system holds
an enormous reserve of water, estimates vary
considerably as to the amount—from as little as
15 000 km 3 (Alker 2008) to 135 000 km 3 (Gossel and
others 2004), to as much as 457 570 km 3 (Bakhbakhi
2006). It is generally believed that the aquifer’s water
dates from wetter climates in the past (5 000–10 000
and 20 000–25 000 years BP) and that no significant
recharge is taking place under current climate
Arid and hyper-arid climate conditions in most of the
region dramatically magnify the aquifer’s importance.
Almost all of the water used by people living
above the aquifer comes either from groundwater
abstraction or diversion from the Nile. The average
annual mean rainfall is less than 50 mm and on
average vast areas over the aquifer system receive
no measurable precipitation. The wettest area at the
northernmost tip of Libya receives around 425 mm of
rain. Northern Darfur in Sudan is the wettest area to
the south but sees only an average of around 200 mm
each year (Figure 2.16.4).
Figure 2.16.3: Dakhla Oasis, 1986-2010
Desert Oasis Development – Dakhla Oasis
Dakhla Oasis lies 300 km west of the Nile and is surrounded by the
driest of desert landscapes. Its location over the southern edge of
the Post Nubian Aquifer, however, provides access to both shallow
and deep wells within the Nubian Sandstone Aquifer System. While
it is currently home to fewer than 100 000 people, archeologists
believe that the Dakhla Oasis has been continuously settled for
around 8 000 years (Dakhleh Project n.d.). Water extraction from the
deeper Nubian Sandstone Aquifer at the Oasis has grown ten-fold
since 1960 (CEDARE 2001). The related growth in agriculture can
be seen in the pair of satellite images that span just a few of those
years—1986 to 2010 (Figure 2.16.3). Faced with increasingly crowded
populations along the Nile, the Egyptian government has been
further developing settlement and agriculture in the Western Desert’s
oasis. Some studies suggest that the planned rate of abstractions
for these areas is unsustainable, however, because it will lead to
local depressions in the water table making water more and more
expensive to access (Ebraheem and others 2003).
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