Scientists at the German Geological Research Center in Potsdam found out that Tehran, the capital of Iran and the largest city in Asia (a population of over 13 million people), is rapidly subsiding. Some areas fall at a speed of 25 centimeters per year, which leads to damage to buildings and communications. The reason for this is the depletion of groundwater.
The researchers analyzed data from various satellite radars that scanned the earth’s surface in the Tehran region and estimated the extent of subsidence from 2003 to 2017. Scientists have used the method of sensing using interferometric radar aperture synthesis (InSAR), which allows to detect even a slight deformation of the soil.
Geologists have identified several sites that descend at a speed of 25 centimeters per year (western part of the Tehran Plain), approximately five centimeters per year (near the international airport) and 22 centimeters per year (southeastern part of Tehran). This subsidence is caused by a regional decrease in the level of groundwater due to their intense pumping. So, in 2013, 32,000 wells were used to extract freshwater (in 1968 there were fewer than four thousand). From 1984 to 2011, the average groundwater level dropped by about 12 meters.
According to scientists, subsidence leads to cracks in the soil and walls, damage to buildings and shifts of the earth’s surface. Compaction of rocks may be irreversible, but proper water use will help avoid catastrophic consequences. If this is not done, the infrastructure of the city can be seriously disrupted, especially in densely populated areas of the city or airport.