According to NCC’s report, Dr. Ali Soltanpour, manager of hydrography and tidal affairs of the NCC, stated: "The study of changes in the Caspian Sea level using satellite data indicates the decline in the second quarter of 2021 compared to the same time last year by 25 centimeters”

This shows that the decline of the Caspian Sea level, which has begun over the past 15 years is mainly due to the reduction of inflow water.

Even though the Caspian Sea has had many declines and increases in its history, this change is considered by many researchers as a normal phenomenon. However, the water extraction from the rivers entering the sea has never been so much; therefore, the current decline of the Caspian Sea due to climate change can be considered as an irreversible decline that threatens the world's largest inland body of water."

He added: "In this study, the data of Topex and Jason one, two, and three altimeter satellites have been used." These satellites periodically monitor changes in world water levels for climate studies, and the data is available to researchers.

Soltanpour explained: "Monitoring sea level as well as some lakes and wetlands through satellite studies and sea-level monitoring stations are conducted by the Hydrography and Tidal Affairs Department of NCC. The data analysis of coastal station is done and announced subsequently."

It should be noted that NCC is also in charge of monitoring and modeling the sea level on the south and north coasts of the country, and the network of permanent sea-level monitoring stations belonging to this organization continuously monitors sea-level changes."

He also added: "The water of the Caspian Sea is supplied through rivers' inflow and then evaporates from its surface. Therefore, changes in the level of the Caspian Sea should be sought in changes in this balance.

The Volga River provides 80% of the water entering the Caspian Sea, and the Aral and Kora rivers are the next. The flow of rivers have been slowly declining in recent years. However, changes in the Volga River appear to have played a major role.

Changes in the discharge of the Volga River show that changes in the Caspian Sea level are completely dependent on it so that the decrease in river discharge in the 70s, followed by the minimum sea level in the last century and its increase in the '90s has caused the sea level to rise in the '90s.

"In this regard, the role of increased evaporation due to global warming in the last century can not be ignored, although the extent of this impact requires more careful study."