Projects are underway in Tehran to help get out of the critical conditions it is facing due to land subsidence, director of Tehran Regional Water Company said.
The projects include construction of a water treatment plant, sealing unauthorized wells, and replacing groundwater with treated wastewater for farming and industrial purposes,” Mehr News Agency reported Hassan Razavi as saying.
“With launch of the 7th water treatment plant in southeast of Tehran in January, so far 100 wells have been sealed and when the 6th treatment plant in the west opens in early summer, about 100 more wells will be shut,” he added.
There are 10,000 illegal wells in Tehran Province, 10% of which belong to industries, Razavi noted.
The earth sinks in some plains in Tehran Province by about 0.5 to 1 millimeter every day, and conditions are more critical in Shahriar and Varamin counties in southwest and south Tehran, Razavi had said before.
Injudicious Groundwater Extraction
An annual 31 centimeters of land subsidence is reported in Tehran Province. Over three billion cubic meters of water is extracted from underground sources in the capital.
Principal causes of overuse are the aquifer-system compaction, drainage of organic soils, mining, gas and oil extraction plus earthquakes.
However, the main reason of land subsidence in Iran is injudicious groundwater extraction that has been causing serious concern among conservationists, environmental experts and academia.
Though reversing land subsidence is impossible, slowing its progress is doable if the government and public cooperate.
Besides land subsidence, groundwater overdraft may lead to destruction of vegetation, increase the possibility of dust storms, holes in the plains and higher salt content in groundwater.
Curbing the spread of land subsidence is of primary importance. When the ground surface moves lower, the entire city sinks with it, which in turn affects the stability of buildings and the functionality of infrastructure.
Illegal water wells have emerged as a dilemma for the water authorities struggling to curb the high extraction and consumption rates, namely in the agricultural regions.
Treated Wastewater
It is planned to replace 300 million cubic meters of groundwater with treated wastewater in Tehran in two years and 500 mcm will be replaced in six years, Razavi was reported as saying.
Currently six wastewater treatment plants operate in Tehran producing 45,000 cubic meters of sewage a day.
The output, which complies with environmental norms, goes to south Tehran for farming and is suitable for green spaces and industrial use.
Tehran Municipality uses groundwater for green spaces and overuse over decades has resulted in the rapid decline in groundwater levels.
Referring to the memorandum of understanding signed with Tehran Municipality to use wastewater instead of groundwater, Razavi said: “Tehran Municipality withdraws 230 million cubic meters of water from aquifers per year, of which 200 mcm will be replaced by treated sewage in the next 5 years."
