By Knight-Ridder Tribune
RENO, Nevada—
A change of biblical proportions is washing across the Sahara
Desert. For the first time in 6,000 years, new lakes have risen
from the sands of southern Egypt.
The Nile River,
swollen by unusual rainfall, is spilling over a reservoir behind
the Aswan High Dam. As expected, the water flows through an arroyo
into an overflow lake. But the deluge has continued, and three
more lakes now unexpectedly dot the desert.
In a land
where water is scarce, this development could hold great promise,
scientists say. The Egyptian government has already begun an irrigation
project around the first lake. The "New Valley" project
aims to draw people from Egypt's crowded cities to a newly green
landscape.
But project
leaders hadn't planned on the bounty of three extra reservoirs.
"The
big question is whether they will make use of the rest of the
lakes," said Mohamed Abdelsalam, a geologist at the University
of Texas at Dallas.
Abdelsalam
and other UTD scientists have been monitoring the lakes' growth
through satellite imagery. This month, the team brought the lakes
to scientific attention by describing them at a meeting in Reno,
Nev., of the Geological Society of America.
First spotted
in 1998, the new lakes have fluctuated in size and shape through
dry spells and monsoons. Together, the lakes hold about 700 billion
cubic feet of water one-quarter the Nile's total water supply.
"That's
a lot of Nile water," said Allison Thurmond, a UTD graduate
student.
The lakes
could provide a crucial resource in a country whose population
is expected to surpass 100 million within the next three decades,
Abdelsalam said. More than 90 percent of those people crowd within
six miles of the Nile.
Of course,
the lakes might not survive more than a year or two.
They exist
only because the Ethiopian highlands have received lots of rain
in the last two years, Abdelsalam said. That water flows down
the highlands and into the Nile, eventually coming to a halt behind
the Aswan dam. Because of this rain, Lake Nasser, the giant reservoir
at Aswan, is at its highest level ever.
But when the
level reaches roughly 600 feet, excess water spills through a
canal into a nearby dimple in the landscape, known as the Toshka
depression. Here, the Egyptian government has built the New Valley
project, a massive effort to irrigate the land and resettle people
away from the Nile.
The first
of the four new lakes the one for which engineers had planned
is known as Toshka Lake. The other three still go by the uninspiring
names of lakes B, C and D, Thurmond said.
Astronauts
aboard the space shuttle Discovery snapped the first pictures
of Toshka Lake in October 1998. Lakes B and C appeared between
February and March 1999. The final lake, D, formed sometime between
August 1999 and last January, Thurmond said.
Lake D is
the biggest, with a surface area of nearly 700 square kilometers.
Lake C is long and skinny; placed on top of a local map, it would
stretch from downtown Dallas to downtown Fort Worth. Toshka Lake
alone would drown most of Dallas.
The UTD scientists
hope to get more lake pictures soon, from a radar system that
flew aboard the space shuttle last year. Those radar pictures
will map the landscape in unprecedented detail, Abdelsalam said.
In a land with basically no topographic maps, the radar system
has gathered information on the dips and ridges of the sand dunes.
That information, in turn, could let scientists predict where
water might spill in the future.
Monitoring
the lakes from space is the fastest and easiest way to keep an
eye on Egypt's changing water resources, said Bob Stern, a UTD
geologist.
"One
of the things I'm excited about is seeing if a fifth lake will
form," he said.
Even if it
does, the New Valley project probably couldn't rely on it or lakes
B, C and D as permanent reservoirs. The water may become too salty
for drinking or irrigation, Stern said. Something similar happened
to California's Salton Sea after the Colorado River flooded a
salty plain.
And the region's
climate is notoriously unpredictable. Cynthia Evans, of NASA's
Johnson Space Center in Houston, has been studying 35 years' worth
of astronaut photographs of the region. Change is the one constant,
as reservoirs grow and shrink as agriculture and drought take
their toll. But the new lakes seem to hold their own, said Evans.
"Unless
there's a real dry spell, they'll probably make it to the next
monsoon," which will probably take place next summer, she
said.
And even if
they don't, their disappearance will be somehow fitting, said
Thurmond.
"The
Nile giveth and the Nile taketh away."
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