Scientific faculty member of the research institute: the process of Caspian sea water retreat continues/noticeable impact on Iran's coastal wetlands

A member of the scientific staff of the National Research Institute of Oceanography and Atmospheric Sciences announced the retreat of the Caspian Sea by 27 and 20 centimeters respectively in the last year and the year before, based on the data of the ground and satellite measuring devices, and said: This year we should expect a further decrease in the Caspian water level, a trend that has a negative effect on the coastal wetlands of Iran more than the rest of the Caspian region.
According to the research institute's public relations report and quoted by IRNA, Dr. Hamid Alizadeh Lahijani, in an article published in Earth-Science Reviews, has reviewed the observations of the water level of the Caspian Sea since the beginning of instrumental measurements (in 1880 AD).
In this article, he discussed various aspects of the water level of the Caspian Sea, including; a) the history of sea level observations with a critical evaluation of measurement methods and data accuracy, b) long-term, seasonal and short-term changes in sea level, c) short-term and long-term forecast of sea level and d) the impact of sea level changes on the coastal and marine environment has been reviewed in different sources.
Based on this, seasonal and short-term changes in the Caspian water level; sub-annual) due to river flooding, precipitation on the sea, effects of atmospheric phenomena on the sea (such as tides), changes in volume of water, tsunamis, and tidal effects occur that range from a few centimeters in half a day (i.e., tides) to 4 meters in five to seven days during a typhoon event in the north of the Caspian Sea.
long-term water level changes; That is, several years to several decades, it mainly depends on the water balance. The input of river water to the sea and the outflow of water from the sea through evaporation are two important components of the water balance of the Caspian Sea. From the middle of the 20th century, river water harvesting for human activities also became important in the water balance of the Caspian Sea. However, there is river water harvesting in the Caspian basin when the water level increases and when the water level decreases, and it is not the determining factor in the fluctuation of the Caspian water level.

An increase of 15 centimeters per year and then a decrease of 8 centimeters
The long-term average of the water level change during the device measurements was more than 3 meters. Also, in the period of 1978-1995, the Caspian water level increased by 15 cm per year and decreased by 8 cm per year since 1996. Coastal flooding during sea level rise has led to great economic losses. But some ecosystem services improved coastal wetlands.
The current drop in the sea level causes the water depth to decrease and the wetlands to dry up. The decrease in sea level in the 1960s and 1970s caused an increase in vertical mixing in deep sea water. However, during the last rise and fall of the water level, the Caspian marine environment had a limited vertical circulation, which led to a lack of oxygen in deep areas. Global warming through changes in precipitation, evaporation and wind regime, in addition to human impacts, will have a significant impact on the water level of the Caspian Sea until the end of this century.
Despite the importance of local, regional and global impacts of changes in the water level of the Caspian Sea, long-term forecasts are still associated with a great lack of certainty and have not yet been successful. Short-term predictions of the water level of the Caspian Sea (about one year) are mainly based on the amount of rainfall in the Volga catchment area in the year before the forecast date, and are highly accurate with reality.

The possibility of reducing the Caspian water level this year
Device measurement at coastal stations (http://www.caspcom.com) and satellite measurement (https://hydroweb.theia-land.fr/) of the Caspian water level show that the trend of lowering the level has continued in recent years. Accordingly, the Caspian water level decreased by 27 cm last year and 20 cm the year before.
This year, the spring flooding of the Volga River started earlier and reached its peak during the Mahdavi period, which was due to the smaller volume of water in the catchment area. Therefore, we should expect a further decrease in the Caspian water level this year as well (Caspcom Bulletin 25).
The effect of the reduction of the Caspian water level on the coastal wetlands of Iran is much more noticeable than the wetlands of other parts of the Caspian, because these wetlands are shallow and mostly surrounded by population centers. Coastal wetlands of Iran in the Caspian, in addition to the pressure caused by the decrease in water level, bear the pressure caused by human factors; They are like excessive consumption of river water and sewage entering the wetland.
Geosciences Review is a monthly review-only journal published by the Elsevier indexing database that covers scientific and research articles in all aspects of the geosciences. This magazine has been published continuously since 1966 (1345).