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1.4.4. The Caspian Sea A. Caspian Sea Basin The Caspian Sea, the largest lake of the world, is located in an inland depression (between 47° 07˘ and 36° 33˘ N, and 45° 43˘ and 54° 50˘ E). Although the Caspian Sea is thousands of kilometer away from the world˘ s open waters and by the geographical definitions it could be called a Lake, but it possesses many marine characteristics: a large water surface area and volume, a specific hydro chemical regime; heavy gales; etc. The Caspian Sea accounts for more than 40% of the over all volume of the global lacustrine waters. The area of the Caspian Sea is 386,400 km2. This area may fluctuate by 10-20%, as the sea level rises or falls. The coastline of the Caspian Sea is about 7250 km extending approximately 1,200 km from north to south, and is 200-450km wide. The drainage basin of the Caspian Sea is estimated to be of 3.1 million km2. The Caspian basin area exhibits an uneven pattern of water distribution and could be differentiated into three sub-areas: the Northern Caspian (80,000 km2), the Middle Caspian (138,000 km2) and the Southern Caspian (168,400 km2). The Northern Caspian is relatively shallow (average depth is 5-6 m and maximum depth is 15-20m) and possesses many islands, banks and troughs. There are as many as 50 islands with a total area of about 350 km2. The Middle Caspian having the maximum depth of 788 m is located in the Derbent Depression or Basin. It holds about 34% of the entire Caspian water volume. The average depth of the Middle Caspian is 190 m. The Southern Caspian holds more than 65% of the entire Caspian water and its maximum depth is of 1025 m. The average depth of the shelf of the Caspian Sea is about 180 m. The natural boundary between the Northern and the Middle Caspian is the Mangyshlak Bank and between the Middle and Southern Caspian is Apsheron Bank, both of which are tectonic elevations. The 7250 km Coastline of the Caspian sea is shared by five countries: the I.R. Iran, with approximately 1000 km (15% of the total coastline), and the Azerbaijan; Kazakhstan; Russia and Turkmenistan, with approximately 6000km (85% of the total coastline). The freshwater inflows to the Caspian Sea are from the Northern and southern Caspian. There is no freshwater inflow from the east. The Volga, Ural and Terek rivers contribute 88% of the freshwater flows in to the Caspian Sea. Azerbaijan and I.R. Iran respectively contribute 7% and 5% of the freshwater flows into the Caspian Sea. B. Oceanography The physico-chemical characteristic of the Northern, Middle and Southern Caspian Sea are very different. The chemical characteristic of the Southern Caspian Sea is as follows: The water temperature of this region along the Iranian coast is highest compared to that of Northern and Middle Caspian Sea. The temperature range in southern Caspian Sea is between 3.5° and to 28° C. There is an increase in water temperature by approximately 4° C, from west (Astara port) to east (Torkaman port). In spring, there is a temperature difference between the coastal region and the open sea (0.5° C). The warming of the sea surface creates thermoclines between 30-40 m of depth, in the Southern Caspian Sea. During the summer, the surface temperature is 25-26 ° C in the southern part. In autumn, with decrease in water temperature, the thermocline becomes less defined, and by winter, it disappears. During the winter, the open sea surface temperature decreases to 16° -17° C in the southern Caspian Sea, while the bottom water temperature through out the year is constant, 4.5 ° C (Figure 8 and Figure 9). In the Southern Caspian Sea salinity level ranges from 12.5-13.5%. The salinity however, decreases to its lowest level in the estuarine rivers (i.e. mixing of fresh and brackish waters). The salinity level like temperature increases from west to east. The phenomenon of halocline has been observed with decrease in depth, where salinity tends to increase. The Caspian Sea is identified to be brackish water lake (Figure 10). The average dissolved oxygen (DO) of water in the Caspian (southern basin) is estimated to be 8.7 mg/lit. The dissolved oxygen level decreases, from the west (Astara port) to the east. This is due to an increase in temperature and salinity of water, as we move in this direction and therefore the level of oxygen tends to decline There is also a decrease in the oxygen level by depth. The pH level in the Southern Caspian Sea is higher than oceanic waters due to the presence of high concentration of ionic HCO3- and CO32- (its pH is 0.3 times higher than oceanic waters). C. Currents The Caspian Sea has two types of cyclonic eddy currents (anti-clock wise) in central and southeastern regions (Figure 11). In the coastal regions of the Southern Caspian the average, currents are directed towards the northwest, north, southeast and south. Current˘ s speed is 20-40 cm/sec reaching a maximum of 50-80 cm/sec. Baroclinic, Seiches and inertial currents play an important role in the local circulation pattern. The average speed of the current along the western shores is estimated to be 30 m/s, which decreases to 10 m/s along the eastern shores (Figure 12). Except the temperature, salinity, dissolved oxygen and pH all exhibit unique patterns of fluctuation, as their amount decrease from the west coast (port of Astara) towards the east coast (Bandar-e Torkaman). D. Water level fluctuations One of the most striking phenomenons in the Caspian Sea is the sea level rise. Sea level fluctuation is primarily due to: climatological changes; regional precipitation and water evaporation from the sea, wind stresses/ surges; alteration in atmospheric transport pattern as well as human activities such as construction of dams on the major rivers. Between the year 1829 and 1929 the sea level was maintained at about-26m, this level was considered perennial or secular average. However, the sea level dropped by nearly 2 meters in 1941, interrupted by two short-term rises in 1946-48 and in 1956-58. The lowest registered level was - 29.02m., in the year 1977, which was the lowest level in the past 200 years. The recent sea level rise (2.1m, since 1978) could be attributed to: river flow; surface precipitation and decrease in evaporation rates. It has also been claimed that the recent sea-level rise is tectonic in origin, and attempt has been made to predict the sea level fluctuation in the future. However, due to uncertainties in the climatic fluctuation and in the Caspian basin evaporation and precipitation, levels it is not yet possible to predict the sea level fluctuation accurately. Better meteorological studies of the Caspian Sea region as well as more advanced watershed and ocean modeling must be used in order to predict the sea level fluctuation with optimum accuracy. The average perennial value for the sea level rise is 40 cm, the seasonal fluctuation as well as the wind - induced surges have a significant impact on the Caspian Sea level fluctuation. Wind- induced surges can increase the sea level for a period of up to few days and causes inundation of vast areas of the coast causing heavy economical losses to the Caspian littoral states. The wind-induced surges are maximum in the Northern Caspian, while in the middle and southern parts they are smaller. Wind induced surges of 1.5 to 3 m. high has been observed in the Caspian Sea within the past few decades. In the North Caspian, the wind-induced surges may even penetrate up to 20-30 km inland and remain in the shore depressions up to 15-20 days. The Caspian Sea level rise has been exerting considerable damages to the Caspian states, i.e., human habitation, industry, and navigation. It causes damages to the flora and fauna habitats. It increases the soil salinity and causes the rise in the ground water. Sea level fluctuation has both positive as well as negative impact on the environment of the Caspian Sea and its coastal states. The rise of water level in the Caspian Sea during the past two decades has caused serious damages in the southern coastal shores of this great lake. Although each of the pertinent organizations including the Ministry of Power has tried to prevent the expansion of possible damages by conducting studies, implementing national-regional projects and especially constructing breakwaters, the rise of water level and its expansion toward the shorelines (regardless of its halt or retreat in the past few years) is a continues source of anxiety for the coastal settlers. The Water Resources of the Caspian Sea Research Center has been established to monitor the water level fluctuations during successive annual hydrological cycles in order to fulfill its organizational goals and objectives. This center monitors these trends and eventually publishes a report on the water level fluctuations annually. For instance, the analysis of the results of data collected from Anzali Station for the annual hydrological cycle of 1999-2000 is presented here. The water level in the Caspian Sea has started its rising trend from the annual hydrological cycle of 1977-1978 and by the end of annual hydrological cycle of 1994-1995 (according to the revised curve), it has risen more than 2.32 meters. During the annual hydrological cycle of 1995-1996 and 1996-1997, the water level decreased temporarily. But, in the following hydrological cycle of 1997-1998, an increase in the water level was observed. Meanwhile, the average water level in hydrological cycle of 1999-2000 shows a decline in comparison to the water level of the previous year. Although most of the researchers believe that the increase in the Caspian Sea’s water level is due to the climatic changes and have presented facts to support this theory, the other possible causes of this phenomenon are not over-ruled in the scientific and technical articles. Therefore, recognizing the type of climatic phenomena taken place and their subsequent effects on the water level fluctuation as well as investigating the other possible sources of sea water input are included in the work plan of the research centers stationed in the littoral states and as well as the international research centers. The researchers at the CASPI Research Center in Russian Federation have presented their views and predictions for the water level changes in the next two decades in the “CASPI Technical & Economic Report”. Although different conditions were studied (removal of various amounts of water from the annual incoming flow), their analysis was basically made upon one possible condition (removal of 35-40 Cubic Kilometers of water per year). In this condition, it is predicted that the water level will continue its increasing trend until 2010 and eventually will reach the elevation of 24.92 meters. This elevation in comparison with the reference year (1992) indicates an increase of 1.46 meters (1.49 meters higher than the average water level in the hydrological cycle of 1999-2000). In view of the above and considering the ever-increasing scope of the scientific research and studies performed on this vast body of water, the Water Resources of The Caspian Sea Research Center is conducting its research in compliance with the activities of the researchers. This center prepares data and information in various fields including the water level fluctuations in several stations in order to pave the way for more comprehensive studies of Caspian Sea parameters and conditions. This center in addition to its ongoing research projects and collection of data and information in its various stations has included the establishment of meteorological stations (on-shore and off-shore stations) in its work plan. This center with the collaboration of the Regional Water Organizations of Gilan and Mazandaran provinces established three Fluctuation Recording Stations in the Astara, Amir-Abad-e-Neka and Bandar-e Torkaman (Ashouradeh) ports last year. All three stations are equipped with Limnograph and are presently functional. The general characteristics of the monitoring stations are as follows: Anzali Station: Ghazian Station: Astara Station: Nowshahr Station: Babolsar (Khezer-Shahr) Station: Amir-Abad-e-Neka Station: Bandar-e-Torkaman (Ashouradeh) Station: The procedure for statistical analysis are presented bellow: First by utilizing the statistics reported by the Anzali Station, a chart indicating the daily changes in the water level is drawn and then the external factors that have affected directly or indirectly the registering devices or the inspections are determined. Since they produce inaccurate and unreal registered data, they are studied and eventually the curves will be altered accordingly. Tables 6 and 7 include the water level fluctuation specifications for the first and the second half of annual hydrological cycle according to the reported data. The charts in pages 9 and 10 show the water level changes in two consecutive annual hydrological cycles (1998-1999) and (1999-2000) respectively as well as the long-term changes in the water level from 1971 to 1999. From the information and data gathered from these stations for the last few years, the following results can be drawn:
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