Rising Water Table Threatens Egypt's Monuments
National Geographic Today
|May 31, 2002|
In the crowded, garbage-strewn alleys and market streets of Mataraya, one of Cairo's poorest and busiest neighborhoods, lies one of Egypt's most sacred sitesAncient Heliopolis. The city and other archaeological treasures in Northern Egypt are under serious threat from forces above the ground, but perhaps even more from below.
A leaking sewage system, exacerbated by a rising population, has caused the water tablethe upper level of groundwaterto rise and threaten to turn the ancient tombs and temples to dust, said Zahi Hawass, National Geographic Explorer-in-Residence and Secretary General of Egypt's Supreme Council of Antiquities.
"The water table brings salt, and this salt damages the limestoneit turns the limestone to a powder," Hawass said.
Heliopolis dates back 6,000 years. It was the first great priestly city of Egypt. It is where the sun god Ra had his temple, where great scholars first invented the obelisk and the solar calendar, and where the legendary phoenix set itself on fire and rose from its own ashes.
But Heliopolis is destined to join the desert sands if the salty waters are not stopped. Hawass has proposed building a new sewage system just for this area.
In addition to faulty sewers, Richard Stephenson, a professor of civil engineering at University of Missouri-Rolla, hypothesizes that the Aswan Dam also contributes to the rising water table. It enables farmers to irrigate year-round and may also cause a buildup of salt.
The Nile Plateau was originally a seabed, and the sands and soil are naturally salty. Before the dam was built in the 1960s, the annual Nile floods would wash the salt into the Mediterranean. Now it prevents flooding, allowing natural and fertilizer salts to accumulate, says Stephenson, who is collaborating with Egypt's National Research Institute of Astronomy and Geophysics to investigate Luxor's disintegrating monuments.
The pore structure of the soil encourages "strong capillary action," Stephenson said, which draws the salty water to the surface and into the porous sandstone foundations of the monuments. The dry desert heat then causes the water in the stones to evaporate, leaving behind "salt crystals that cause the sandstone to split, flake and crack," Stephenson said.
Last July, while in Luxor, Stephenson found white salt deposits on the foundation stone of temples in Luxor.
Possible solutions include installing wells to lower the water table, replacing foundation stones with less porous material, and injecting chemical sealant between structures and the soil to create water barriersall of which are tremendously expensive and risk damaging the monuments.
When archaeologists discovered a 2,500-year-old tomb of a palace worker in Mataraya, it was soaking in sewage. The water was seeping through the exterior limestone and causing the precious hieroglyphs to disintegrate. Hawass says that for a tomb its size, it is one of the most beautifully decorated in all of Egypt.
In a race against time, Hawass and colleagues dismantled the tomb, numbered, labeled, and treated the blocks, and restored the drawings.
The restoration was completed earlier this month and the tomb now sits on a concrete base in a dry area well above the water table. "If we had waited more than one month, this tomb could have been gone."
It's not just small tombs that could crumble to dust. Hawass first realized how serious a threat the rising water levels were to Egypt's monuments when water crept to within two feet of the great sphinx of Giza.
To rescue it, a massive three-year project to build sewage systems in surrounding villages caused the water level to drop to about 27 feet (8 meters) below the surface.
But rising water is riddling the whole of Egypt. And nowhere is the problem more severe than in northern Egypt, where the Nile branches off into the delta before emptying into the Mediterranean.
In Zagazig, the site of another once great temple about 50 miles (80 kilometers) north of Cairo, workers recently discovered an 11-ton (10-metric-ton), well-preserved head, most likely of queen Nefertari, wife of Pharaoh Ramses II, who ruled about 3,300 years ago. The find is special because the artifacts in the north don't usually fare as well as the ones in the south, which has a much drier climate.
Hawass said Zagazig is just one of hundreds of sites in the delta, and he's convinced this area still holds many more treasures.
"But I need the help of foreign expeditions," Hawass said. "Therefore I'm going to direct and make rules that any new expedition [Egyptian or foreign] that wants to come and work in Egypt should work in the Delta to save the monuments before they are destroyed by the water table."
Building a sewage system for the entire Delta is impractical, says Hawass. The only way to save the monuments is to excavate and remove them from danger. "You have to start working right now," Hawass said.
With help, like that mythical phoenix, Egypt's ancient mysteries will also rise, not from fire, but from water.
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