“The unprecedented 150-centimeter drop in water level (over the last 30 years) is primarily due to increased evaporation (completely dominated by temperature), low precipitation and substantial decline in water flow into the lake from rivers that empty into the sea,” Masoumeh Banihashemi was quoted as saying by IRNA.
The water level has been falling over the past three decades and a variety of programs to manage the crisis have failed to deliver, so far.
The sea registered a 13-centimeter drop in 2019, compared to the previous year, she said.
Last year the Caspian Sea water level plunged below -27.18 meters (relative to the Baltic Sea). The Baltic Sea datum is used as a reference point to measure fluctuations in the Caspian water level.
On the main perpetrator behind the rapidly declining water levels, she said evaporation over the Caspian Sea (due to climate change and global warming) is causing more harm than the limited river discharge and precipitation.
“Evaporation has contributed to about half of the decline, while the combined effect of poor precipitation and river discharge changes have contributed to the other half.”
Studies by WRC show that if temperature in the Caspian Sea region (risen by 1 degree Celsius in 30 years) continues to rise, loss from evaporation will make a bad situation worse.
“Unless river discharge increases accordingly or precipitation in the Caspian drainage basin increases, the imbalance is likely to continue (as the planet warms)."
In addition to irreparable ecological harm, the reducing water level has led to the shrinkage of territorial waters, she warned.
In some regions around the Caspian, coastlines have receded between 60 to 200 meters as territorial waters deplete.
Historic Low
The Caspian 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 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.
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 domestic 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 fishing source.
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.