The level of Earth's largest inland body of water registered a 27-centimeter decline in 2021, the head of the National Center for Research and Studies of the Caspian Sea, affiliated to the Energy Ministry’s Water Research Center said.
“The unprecedented drop in water level in the Caspian Sea is primarily due to increased evaporation [caused by rising temperature]), low precipitation and a substantial decline in water flow into the lake from rivers that empty into the sea,” Masoumeh Banihashemi was also quoted as saying by IRNA.
Water loss in the Caspian Sea has worsened substantially since 1995 and is expected to continue in the foreseeable future due to rising temperatures associated with climate change, she added.
The water level has been falling over the past three decades and a variety of programs to manage the crisis have failed to stem the decline. It reached a historic low of 29 meters below mean sea level in the late 1970s before water levels increased in 1978. If current evaporation rates continue, the study suggested, the sea will approach a historic low again.
According to the official, annually an estimated 300 billion cubic meters of water flows into the sea from its tributaries, the largest being the Volga River that runs through Russia and discharges around 240 bcm of water into the lake.
Nevertheless, the inflow dwindled by 22% in 2019 not only due to low precipitation but also because of mega structures (floodgates and levees) being built by the Caspian Sea littoral states (Iran, Russia, Azerbaijan, Kazakhstan and Turkmenistan) on the river.
“Close to 200 dams and other huge structures [floodgates and levees] are being built on rivers that feed the sea, which would take a toll on the world’s largest lake upon completion,” he said.
The Volga River (Europe’s largest in terms of discharge that runs through Russia) is the largest tributary of Caspian Sea and provides 85% of its water (260 billion cubic meters a year).
Water inflow from the Volga River to Caspian Sea amounted to 191 bcm in 2021, down 15% compared to a year ago.
Other tributaries, which account for the balance of the inflow of water (60 bcm) are the Koura River that flows through the Caucasus Mountains, Ural River that passes through Russia and Iranian rivers, namely Atrak, Haraz and Sefidroud.
The Caspian Sea borders five countries and has an abundance of natural resources and diverse wildlife. The sea also contains large oil and natural gas reserves and is an important source of aquatics.
Ancient Species
The sea supports many unique and ancient species remaining from the times when it was part of the Tethys Ocean during the Mesozoic era, approximately 300 million years ago.
Although most of the species are found in the southern and middle regions of the Caspian, some use the shallow northern areas as spawning grounds, including 90% of the world's sturgeons.
Homayoun Khoshravan, the executor of an international plan to monitor variations in the Caspian Sea water level, believes that the decline (1.7 meters since 1995) has exacerbated the loss of territorial waters in Iran.
“Satellite-based studies [since 2005] have shown that the level of Iran’s territorial waters is less than the global average and declining gradually,” he said.
“A country's territorial waters are parts of the sea close to its coast, which are recognized by international agreement to be under its control.
In addition to irreparable ecological harm, the lowering water levels in Caspian Sea have led to the shrinkage of territorial waters.”
Khoshravan noted that in some regions around the Caspian Sea, the coastline has reduced by 60 to 200 meters.
