Tehran, the most populous city in Western Asia with a population of around 15 million people, has become the victim of dramatic subsidence, which is causing parts of it to sink at an alarming rate of 25 centimetres a year. Scientists from the GFZ German Research Centre for Geosciences in Potsdam used satellite data to reveal the extent of the subsidence – where the ground begins to collapse in on itself. The team used a tool known as Interferometric Synthetic Aperture Radar (InSAR) which can spot even the most minute difference in ground deformation.
They revealed that the land around Tehran international airport is sinking at around 5 centimetres per year – which unfortunately was one of the more moderate areas of subsidence.
Three areas in Tehran were found to be sinking at a rate of a quarter of a metre per year.
The reason it is sinking is because many of Iran’s groundwater basins have been severely depleted.
Droughts and an increase in water demand have left major cracks and spaces in soil, sand and rock beneath Iran’s capital, leading to subsidence.
The team write in their research paper published in Remote Sensing of Environment: “In recent decades, rapid population growth combined with urban and industrial development have increased the need for water supplies in the Tehran Plain.
“As a result of extensive groundwater depletion, the plain has been undergoing rapid land subsidence.
“The average groundwater level in Tehran decreased by approximately 12 metres (39.3 ft) from 1984 to 2011.
“Earth fissures, damage to buildings, shifts on the ground, and cracks in walls are evidence of groundwater-induced compaction that have been observed in the Tehran Plain.
“Unless effective groundwater management is implemented, ongoing subsidence in Tehran is expected to cause further damage to infrastructure particularly in the regions of high displacement gradients in the urban areas of Tehran and near IKA airport.”
Researcher Mahdi Motagh hopes it is not too late:”Science and research could support Iranian administrations and governments to revise their water management policy for a sustainable development.”