International Journal of Marine Science, 2017, Vol.7, No.3, 19-30
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precipitation amount, run off rate, temperature and evaporation process for water level balance. So in the global
warming phases, the evaporation fivefold increased more ratio precipitation and Caspian Sea level intensively
dropped. This process has caused the difference behavior of Caspian Sea hydrology to ocean fluctuation function.
For example, the separation of Uzboy River from Caspian Sea decreased the water level during late Holocene.
Other vital river like Volga has important action in water level balance of Caspian Sea and human activities during
1930 to 1995 had caused a full fluctuation cycle with 6 meters’ amplitude (Rychagov, 1997).
Figure 7 Fluctuation curve of the Caspian Sea during Holocene epoch (Rychagov, 1997)
2.4 Caspian Sea level fluctuation (1830-2015)
The water level fluctuation is one of the most important non-biological properties of Caspian Sea which makes it
distinctive from other great lakes on the earth. The analysis of level change situation in Caspian Sea water in
historical periods and in the present time shows that there is a close relationship between the water level
fluctuations and the global climate changes. This means that the climatic processes, which cause in change of
humidity and heat exchange, influence this area; although, the role of human intervention in the processes of
Caspian Sea water level change is noticeable. The ancient historical and geographi cal information shows that the
level change process in Caspian Sea water is periodic and these changes ranged between 15 to 25 meters during
the last 5 to 12 thousand years. The most complete historical reconstruction done based on archaeological
evidences and the evidences of ancient weather condition have determined the water fluctuations from 2 to 3
thousand years ago with the accuracy of ten years. In the historical period, the long-term mean of Caspian sea
water was -27 meters and it’s variance was 0.04 centimeter from 7th century B.C to 7th century A.D and
fluctuated +0.03 centimeter from 8th century B.C up to now. In the historical period, the maximal water level
stagnation is 40% in the altitudinal range of -25 to -27 meters, and the reiterative period of 70 percent of changes
is in -24 to -30 meters level height. The data of historical period shows that the long-term mean of seawater level
fluctuation in the present time is oriented toward level rise up to 0.3 centimeter per year. But, after the 7th century
this amount was about 0.5 centimeter per year. Since 1837 and in the era of instrumental record observations, the
range of Caspian Sea water level fluctuations has been about 4 meters and it has ranged from -25.2 meters in
eighties to -29 meters in 1977. To do investigations on the long-term changes of Caspian Sea water level in the
instrumental record era, the data of hydrology posts with the long-term observation series were used. The only
fluctuation recording station in Caspian Sea which has the complete observatory series is the Baku gauging station
(1830-now). Considering the Caspian Sea water level changes, several index periods can be mentioned. For
instance, from 1830 to 1883 or in 50 years the condition of water level was almost constant in the height of -25.2
to -26.2 meters. The long-term decline period has started since 1883and lasted for more than 100 years, since then
