Iran has a water problem. Although activists and alarmist scientists like to place the blame on climate change, Iran's water problems are due to public planning mismanagement.
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Why Teheran is sinking dangerously
December 7, 2018, created by ph
(Press release translated/edited from the German by P. Gosselin)
Mahdi Motagh and Mahmud Haghshenas Haghighi of the Remote Sensing Section of the German Research Center for Geosciences (GFZ) in Potsdam report on the subsidence of the earth's surface in the Teheran region in the journal Remote Sensing of Environment.
Sinking 25 cm per year
They found that between 2003 and 2017 three areas were sinking with velocities of which at times were more than 25 centimeters per year, and sank by a total of several meters. For the first time the study traces in detail and with precise measurements the temporal course of the subsidence in the region over a longer period of time.
Iran has a water problem
The reserves in many groundwater basins are heavily depleted. The country has been investing heavily in agricultural development for about forty years and strives to be independent in food supply. In order to meet the increased water demand, groundwater basins are being exploited to a considerable extent and hardly regulated by the state.
In addition, the government has built many dams to store water for specific purposes, especially in agriculture. However, these have constrained the natural inflow into the groundwater basins in the downstream areas, contributing to desertification and serious environmental problems, which include the ongoing drying of Lake Uri in northwestern Iran, the second largest salt lake in the world, and to frequent dust and sand storms in recent years in the province of Khuzestan in the southwest.
In the region around the capital Tehran with its approximately eight million people, the demand for water has also risen sharply in the last forty years due to the influx of many inhabitants. The number of wells there rose from just under 4000 in 1968 to more than 32,000 in 2012. In addition, there is a lack of rain during periods of drought, which has become increasingly frequent in recent years. All this has led to a sharp drop in the groundwater level. In Tehran, for example, there was a drop of twelve meters between 1984 and 2011.
Crevices in the ground and cracks in building walls are, for example, consequences of the ground deformation, say Haghshenas Haghighi and Motagh. They also found that the groundwater basins in certain areas were irreversibly damaged by exploitation. In the future, they will no longer be able to store as much water as they used to. Scientifically based plans for water management could, however, help defuse the situation, the two researchers say. "To allow sustainable development, both science and research can assist Iranian administrations and governments revise their water management policies," says Motagh
Real-time data for geological risks
For their analysis Haghshenas Haghighi and Motagh used the radar interferometry method InSAR (Interferometric Synthetic Aperture Radar). With this measurement method, high-precision radar signals recorded by satellites in the microwave range can be used to create an image of the topography of the earth's surface. To document surface changes, the researchers used nine data sets from the satellite systems Envisat ASAR, ALOS PALSAR, TerraSAR-X and Sentinel-1 from the years 2003 to 2017. They combined the data sets to investigate the short and long-term reactions of the Earth's surface to changes in groundwater levels.
Of particular importance were the satellite images from the Sentinel-1 mission, which has provided high-resolution radar images with an edge length of 250 kilometers from the Tehran region every 24 days since 2014, and every 12 days since 2016. "This makes it possible to analyze geological risks such as land subsidence almost in real time," says Motagh.
Next, the two researchers wish to expand the investigated area and also measure the subsidence of the country outside Tehran with Sentinel-1. "Such data on subsidence in large areas pose new challenges. We are developing software tools to analyze the huge amount of radar data," says Haghshenas Haghighi.
This research was supported by the Impulse and network fund of the Helmholtz-Gemeinschaft in der Helmholtz-Allianz "Remote Sensing and Earth System Dynamics".
Original study: Haghshenas Haghighi, M., Motagh M., 2018. Ground surface response to continuous compaction of aquifer system in Tehran, Iran: Results from a long-term multi-sensor InSAR analysis. Remote Sensing of Environment. DOI: 10.1016/j.rse.2018.11.003
Persons to contact:
Dr. Mahdi Motagh and Mahmud Haghshenas Haghighi
Sektion Fernerkundung
Helmholtz Center Potsdam
German GeoForschungsZentrum GFZ
Telegrafenberg
14473 Potsdam
Tel.: +49 331 288-1197
Email: mahdi.motagh@gfz-potsdam.de, mahmud@gfz-potsdam.de
Twitter: @MahdiMotagh, @Mahmudhh
Media contact:
Dipl.-Geogr. Josef Zens
Head of press and public relations
Helmholtz Center Potsdam
German GeoForschungsZentrum GFZ
Telegrafenberg
14473 Potsdam
Tel.: +49 331 288-1049
Email: josef.zens@gfz-potsdam.de
Twitter: @gfz_potsdam
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