Wednesday, May 4, 2016

Hydraulic Engineering in Petra

By: Hanan Rawashdeh
 Petra the ancient city is one of the world’s seven wonders. What makes it so unique? And how is it that a city so secluded within the canyon walls in the middle of the hot desert South West of Jordan with no close surface water to be able to maintain a lively civilization of 20-30,000 dwellers?
Although the strategic location of the ancient city is understandable in terms of the economic factor with the trade route going through the city, living conditions are very challenging as the very dry desert climate is hot with only a few inches of precipitation yearly. And sometimes these four to five inches of annual rain would drop all at once causing a flash flood. The topography is a rocky region filled with huge gorges of sandstone and scarce with greenery.  Nomadic tribes were known to wonder the region looking for water sources due to the nature of the climate in the southern part of Jordan. Therefore in order for a city as large as Petra to withhold such numerous activities and flourish with civilization the Arab Nabateans had to find a way to engineer water to constantly flow and get stored easily within the region of the city and provide protection from any flash floods.

  Scholars believe ceramic joints making a pipeline were used to transport water. Like a perennial stream, this distribution system and water supply of the Nabataean city of Petra had exploited all possible water resources using management techniques that balance reservoir storage capacity with continuous flow pipeline systems to maintain a constant water supply throughout the year.

  Hydraulic technologies helped maintain the high living standard of city dwellers throughout the centuries.  Charles Ortloff , a hydraulic engineer, found that to create a constant flow that wasn’t too fast to fill the water pipes and create pressure that could lead to leakage the pipes needed to be sloped down an angle of four degrees. Remarkably when going back to the carved water channels he found that the Nabataeans had that same slope degree, proving to be masters in hydro engineering.
   Ueli Bellwald , a Swiss architect and archeologist believes that there were five dams constructed of blocks of mortar were constructed to prevent the flash floods from ruining
the city after discovering the remnants of a dam going back to two thousand years old.     
   He claims that clues of existing dams erected between the narrow gorges can be noted from the streaks of darker colored rocks on the canyon walls indicating the existence of Mineral deposits from previous water storage. When he followed the darker colored streaks he was led to a gorge that had two deep grooves carved inside, concluding that there was a dam had previously held the water reservoir into place anchored into the canyon walls to stand against the pressure of the stored water.
  Scholars came to a presumption that the total of water sources in Petra city are 8 springs for fresh water, 36 dams protection, more than 100 systems of reservoirs and 125miles of piping. By estimating the amount of collected waters through these methods approximately two gallons of water was the daily share of every individual of the 30,000 Petra dwellers. That is enough water to create from this desert city and oasis.

The Hydraulic system in the ancient  is a demonstration of  high engineering capability that indicates a high degree of cognitive skill which the Nabataea Arabs had in solving complex hydraulic problems and ensuring a stable water supply around 2,000 years ago.

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