On Sunday, August 12, in Aktau, Kazakhstan, the presidents of Azerbaijan, Iran, Kazakhstan, Russia and Turkmenistan signed the Convention on the Legal Status of the Caspian Sea. Previously, its status was regulated by Soviet-Iranian treaties, in which the Caspian Sea was defined as a closed (inland) sea, and each Caspian state had sovereign rights to a 10-mile zone and equal rights to the rest of the sea.
Now, according to the new convention, each country is assigned its own territorial waters (zones 15 miles wide). In addition, the provisions of the 1982 UN Convention on the Law of the Sea will not apply to the Caspian Sea, the seabed will be delimited into sectors, as is done by neighboring seas, and sovereignty over the water column will be established on the basis of the principle that it is a lake.
Why is the Caspian considered neither a lake nor a sea?
To be considered a sea, the Caspian Sea must have access to the ocean; this is one of the most important conditions for which a body of water can be called a sea. But the Caspian Sea has no access to the ocean, so it is considered a closed body of water not connected to the World Ocean.
The second feature that distinguishes sea waters from lake waters is their high salinity. The water in the Caspian Sea is indeed salty, but in its salt composition it occupies an intermediate position between the river and the ocean. In addition, in the Caspian Sea, salinity increases towards the south. The Volga delta contains 0.3‰ salts, and in the eastern regions of the Southern and Middle Caspian Sea the salinity reaches 13-14‰. And if we talk about the salinity of the World Ocean, it averages 34.7 ‰.
Due to its specific geographical and hydrological characteristics, the reservoir received a special legal status. The summit participants decided that the Caspian Sea is an inland body of water that does not have a direct connection with the World Ocean, and therefore cannot be considered a sea, and at the same time, due to its size, water composition and bottom features, cannot be considered a lake.
What has been achieved since the signing of the Convention?
The new treaty expands opportunities for cooperation between countries and also involves limiting any military presence of third countries. According to political scientist, director of the Institute of Modern States Alexey Martynov, the main achievement of the last summit is that its participants managed to stop any talk about the possible construction of military bases and NATO infrastructure facilities in the Caspian Sea.
“The most important thing that was achieved was to fix that the Caspian Sea will be demilitarized for all Caspian states. There will be no other military personnel there except those representing the countries that signed the Caspian Agreement. This is a fundamental and main question that was important to fix. Everything else, what is divided proportionally into zones of influence, zones of extraction of biological resources, zones of extraction of shelf resources, was not so important. As we remember, in the last twenty years the military has been actively seeking to enter the region. The United States even wanted to build its own military base there,” says Martynov.
In addition to the distribution of each country's shares in the oil and gas fields of the Caspian basin, the Convention also provides for the construction of pipelines. As stated in the document, the rules for laying them provide for the consent of only neighboring countries, and not all countries of the Caspian Sea. After signing the agreement, Turkmenistan, in particular, stated that it was ready to lay pipelines along the bottom of the Caspian Sea, which would allow it to export its gas through Azerbaijan to Europe. The consent of Russia, which previously insisted that the project could only be implemented with the permission of all five Caspian states, is now no longer required. They plan to subsequently connect the gas pipeline to the Trans-Anatolian gas pipeline, through which natural gas will flow through the territory of Azerbaijan, Georgia and Turkey to Greece.
“Turkmenistan is not a foreign country to us, but our partner, a country that we consider very important for us in the post-Soviet space. We cannot be against them receiving an additional impetus for development through such pipeline projects. Gas has long been coming from Turkmenistan and other countries through another pipeline system, somewhere it is even mixed with Russian gas, and there is nothing wrong with that. If this project works, everyone will benefit, including Russia. Under no circumstances should the project be considered as some kind of competition. The European market is so large and insatiable, I mean the energy market, that there is enough room for everyone,” says Martynov.
Today, almost all Turkmen gas is supplied to China, where Russia also intends to supply blue fuel. For this purpose, in particular, a large-scale project for the construction of the Power of Siberia gas pipeline is being implemented. Thus, the geography of gas supplies for both countries can expand - Turkmenistan will gain access to the European market, and Russia will be able to increase its gas supplies to China.
CaspAndyskoe mOre(Caspian) is the largest enclosed body of water on Earth. In size, the Caspian Sea is much larger than lakes such as Superior, Victoria, Huron, Michigan, and Baikal. According to formal characteristics, the Caspian Sea is an endorheic lake. However, given its large size, brackish waters and a regime similar to the sea, this body of water is called a sea.
According to one hypothesis, the Caspian Sea (among the ancient Slavs – the Khvalynsk Sea) received its name in honor of the Caspian tribes who lived BC on its southwestern coast.
The Caspian Sea washes the shores of five states: Russia, Azerbaijan, Iran, Turkmenistan and Kazakhstan.
The Caspian Sea is elongated in the meridional direction and is located between 36°33΄ and 47°07΄ N latitude. and 45°43΄ and 54°03΄ E. (without Kara-Bogaz-Gol Bay). The length of the sea along the meridian is about 1200 km; average width – 310 km. The northern coast of the Caspian Sea is bordered by the Caspian lowland, the eastern coast by the deserts of Central Asia; in the west the Caucasus Mountains approach the sea, in the south the Elburz ridge stretches near the coast.
The surface of the Caspian Sea is located significantly below the level of the World Ocean. Its current level fluctuates around -27...-28 m. These levels correspond to a sea surface area of 390 and 380 thousand km 2 (without the Kara-Bogaz-Gol Bay), a water volume of 74.15 and 73.75 thousand km 3, average depth approximately 190 m.
The Caspian Sea is traditionally divided into three large parts: the Northern (24% of the sea area), the Middle (36%) and the Southern Caspian (40%), which differ significantly in morphology and regime, as well as the large and isolated Kara-Bogaz-Gol Bay. The northern, shelf part of the sea is shallow: its average depth is 5–6 m, maximum depths are 15–25 m, the volume is less than 1% of the total water mass of the sea. The Middle Caspian is an isolated basin with an area of maximum depths in the Derbent depression (788 m); its average depth is about 190 m. In the South Caspian, the average and maximum depths are 345 and 1025 m (in the South Caspian depression); 65% of the sea's water mass is concentrated here.
There are about 50 islands in the Caspian Sea with a total area of approximately 400 km2; the main ones are Tyuleniy, Chechen, Zyudev, Konevsky, Dzhambaysky, Durneva, Ogurchinsky, Apsheronsky. The length of the coastline is approximately 6.8 thousand km, with islands – up to 7.5 thousand km. The shores of the Caspian Sea are diverse. In the northern and eastern parts they are quite rugged. Here are the large bays of Kizlyarsky, Komsomolets, Mangyshlaksky, Kazakhsky, Kara-Bogaz-Gol, Krasnovodsky and Turkmensky, many bays; off the west coast - Kyzylagachsky. The largest peninsulas are Agrakhansky, Buzachi, Tyub-Karagan, Mangyshlak, Krasnovodsky, Cheleken and Apsheronsky. The most common shores are accumulative; areas with abrasion shores are found along the contour of the Middle and Southern Caspian Sea.
Over 130 rivers flow into the Caspian Sea, the largest of which are the Volga , Ural, Terek, Sulak, Samur, Kura, Sefidrud, Atrek, Emba (its flow enters the sea only in high-water years). Nine rivers have deltas; the largest are located at the mouths of the Volga and Terek.
The main feature of the Caspian Sea, as an endorheic reservoir, is instability and a wide range of long-term fluctuations in its level. This most important hydrological feature of the Caspian Sea has a significant impact on all its other hydrological characteristics, as well as on the structure and regime of river mouths and coastal zones. In the Caspian Sea level varied in the range of ~200 m: from -140 to +50 m BS; at -34 to -20 m BS. From the first third of the 19th century. and until 1977, sea level dropped by about 3.8 m - to the lowest level in the last 400 years (-29.01 m BS). In 1978–1995 The level of the Caspian Sea rose by 2.35 m and reached -26.66 m BS. Since 1995, a certain downward trend in level has been dominant - to -27.69 m BS in 2013.
During major events, the northern coast of the Caspian Sea shifted to the Samara Luka on the Volga, and perhaps further. During maximum transgressions, the Caspian Sea turned into a drainage lake: excess water flowed through the Kuma-Manych depression into the Sea of Azov and further into the Black Sea. During extreme regressions, the southern coast of the Caspian Sea shifted to the Absheron threshold.
Long-term fluctuations in the level of the Caspian Sea are explained by changes in the structure of the water balance of the Caspian Sea. Sea level rises when the incoming part of the water balance (primarily the water flow of rivers) increases and exceeds the outgoing part, and decreases if the influx of river water decreases. The total water flow of all rivers averages 300 km 3 /year; while the five largest rivers account for almost 95% (the Volga gives 83%). During the period of the lowest sea level, in 1942–1977, the river flow was 275.3 km 3 /year (of which 234.6 km 3 /year was the Volga runoff), precipitation - 70.9, underground flow - 4 km 3 /year, and evaporation and outflow into the Kara-Bogaz-Gol Bay are 354.79 and 9.8 km 3 /year. During the period of intense sea level rise, in 1978–1995, - respectively 315 (Volga - 274.1), 86.1, 4, 348.79 and 8.7 km 3 /year; in the modern period - 287.4 (Volga - 248.2), 75.3, 4, 378.3 and 16.3 km 3 /year.
Intra-annual changes in the level of the Caspian Sea are characterized by a maximum in June–July and a minimum in February; the range of intra-annual level fluctuations is 30–40 cm. Surge level fluctuations occur throughout the sea, but they are most significant in the northern part, where, with maximum surges, the level can rise by 2–4.5 m and the edge “retreat” by several tens kilometers inland, and during surges it will drop by 1–2.5 m. Seiche and tidal level fluctuations do not exceed 0.1–0.2 m.
Despite the relatively small size of the reservoir, there is strong excitement in the Caspian Sea. The highest wave heights in the Southern Caspian Sea can reach 10–11 m. Wave heights decrease in the direction from south to north. Storm waves can develop at any time of the year, but they are more frequent and more dangerous in the cold half of the year.
In the Caspian Sea as a whole, wind currents predominate; Nevertheless, in the estuary coastal zones of large rivers, runoff currents play a significant role. In the Middle Caspian, cyclonic water circulation predominates, in the Southern Caspian - anticyclonic. In the northern part of the sea, patterns of wind currents are more irregular and depend on the characteristics and variability of the wind, bottom topography and coastal contours, river flow and aquatic vegetation.
Water temperature is subject to significant latitudinal and seasonal changes. In winter, it varies from 0–0.5 o C at the ice edge in the north of the sea to 10–11 o C in the south. In summer, the water temperature in the sea averages 23–28 o C, and in shallow coastal waters in the Northern Caspian Sea it can reach 35–40 o C. At depths, a constant temperature is maintained: deeper than 100 m it is 4–7 o C.
In winter, only the northern part of the Caspian Sea freezes; in severe winter - the entire Northern Caspian and coastal zones of the Middle Caspian. Freeze-up in the Northern Caspian lasts from November to March.
Water salinity changes especially sharply in the northern part of the sea: from 0.1‰ at the mouth shores of the Volga and Ural to 10–12‰ on the border with the Middle Caspian. In the Northern Caspian Sea, the temporal variability of water salinity is also great. In the middle and southern parts of the sea, salinity fluctuations are small: it is generally 12.5–13.5‰, increasing from north to south and from west to east. The highest water salinity is in the Kara-Bogaz-Gol Bay (up to 300‰). With depth, water salinity increases slightly (by 0.1–0.3‰). The average salinity of the sea is about 12.5‰.
More than a hundred species of fish live in the Caspian Sea and the mouths of the rivers flowing into it. There are Mediterranean and Arctic invaders. The fish species are goby, herring, salmon, carp, mullet and sturgeon. The latter include five species: sturgeon, beluga, stellate sturgeon, thorn and sterlet. The sea can produce up to 500–550 thousand tons of fish annually, if overfishing is not allowed. Of the marine mammals, the endemic Caspian seal lives in the Caspian Sea. 5–6 million waterfowl migrate through the Caspian region annually.
The economy of the Caspian Sea is associated with oil and gas production, shipping, fishing, seafood, various salts and minerals (Kara-Bogaz-Gol Bay), and the use of recreational resources. The explored oil resources in the Caspian Sea amount to about 10 billion tons, the total resources of oil and gas condensate are estimated at 18–20 billion tons. Oil and gas production is carried out on an ever-increasing scale. The Caspian Sea is also used by water transport, including along the river-sea and sea-river routes. The main ports of the Caspian Sea: Astrakhan, Olya, Makhachkala (Russia), Aktau, Atyrau (Kazakhstan), Baku (Azerbaijan), Noushehr, Bandar-Anzeli, Bandar-Torkemen (Iran) and Turkmenbashi (Turkmenistan).
Economic activities and hydrological features of the Caspian Sea create a number of serious environmental and water management problems. Among them: anthropogenic pollution of river and sea waters (mainly with petroleum products, phenols and surfactants), poaching and reduction of fish stocks, especially sturgeon; damage to the population and coastal economic activities due to large-scale and rapid changes in the level of the reservoir, the impact of numerous dangerous hydrological phenomena and hydrological-morphological processes.
The total economic damage for all Caspian countries associated with the rapid and significant recent rise in the level of the Caspian Sea, the flooding of part of the coastal land, and the destruction of coastlines and coastal structures, amounted to an estimated amount of 15 to 30 billion US dollars. Urgent engineering measures were required to protect the coast.
A sharp drop in the level of the Caspian Sea in the 1930s–1970s. resulted in less damage, but it was still significant. Navigable approach channels became shallow, the shallow seaside at the mouths of the Volga and Ural became heavily overgrown, which became an obstacle to the passage of fish into the rivers to spawn. Fish passages had to be built through the mentioned seashores.
Among the unresolved problems is the lack of an international agreement on the international legal status of the Caspian Sea, the division of its waters, bottom and subsoil.
The Caspian Sea is the object of many years of research by specialists from all Caspian states. Such domestic organizations as the State Oceanographic Institute, the Institute of Oceanology of the Russian Academy of Sciences, the Hydrometeorological Center of Russia, the Caspian Research Institute of Fisheries, the Faculty of Geography of Moscow State University, etc. took an active part in the study of the Caspian Sea.
Caspian Sea is inland and located in a vast continental depression on the border of Europe and Asia. The Caspian Sea has no connection with the ocean, which formally allows it to be called a lake, but it has all the features of the sea, since in past geological eras it had connections with the ocean.
Today Russia has access only to the Northern Caspian Sea and the Dagestan part of the western coast of the Middle Caspian Sea. The waters of the Caspian Sea wash the shores of countries such as Azerbaijan, Iran, Turkmenistan, and Kazakhstan.
The sea area is 386.4 thousand km2, the volume of water is 78 thousand m3.
The Caspian Sea has a vast drainage basin, with an area of about 3.5 million km2. The nature of the landscapes, climatic conditions and types of rivers are different. Despite the vastness of the drainage basin, only 62.6% of its area is drainage areas; about 26.1% - for non-drainage. The area of the Caspian Sea itself is 11.3%. 130 rivers flow into it, but almost all of them are located in the north and west (and the eastern coast does not have a single river reaching the sea). The largest river in the Caspian basin is the Volga, which provides 78% of the river waters entering the sea (it should be noted that more than 25% of the Russian economy is located in the basin of this river, and this undoubtedly determines many hydrochemical and other features of the waters of the Caspian Sea), as well as rivers Kura, Zhaiyk (Ural), Terek, Sulak, Samur.
Physiographically and according to the nature of the underwater relief, the sea is divided into three parts: northern, middle and southern. The conventional border between the northern and middle parts runs along the line Chechen Island–Cape Tyub-Karagan, and between the middle and southern parts along the line Zhiloy Island–Cape Kuuli.
The shelf of the Caspian Sea is on average limited to depths of about 100 m. The continental slope, which begins below the shelf edge, ends in the middle part at approximately 500–600 m depths, in the southern part, where it is very steep, at 700–750 m.
The northern part of the sea is shallow, its average depth is 5–6 m, the maximum depths of 15–20 m are located on the border with the middle part of the sea. The bottom topography is complicated by the presence of banks, islands, and grooves.
The middle part of the sea is an isolated basin, the region of maximum depths of which - the Derbent depression - is shifted to the western coast. The average depth of this part of the sea is 190 m, the greatest is 788 m.
The southern part of the sea is separated from the middle by the Absheron threshold, which is a continuation of the Greater Caucasus. The depths above this underwater ridge do not exceed 180 m. The deepest part of the South Caspian depression with a maximum sea depth of 1025 m is located east of the Kura delta. Several underwater ridges up to 500 m high rise above the bottom of the basin.
Shores The Caspian Sea is diverse. In the northern part of the sea they are quite indented. Here are the Kizlyarsky, Agrakhansky, Mangyshlaksky bays and many shallow bays. Notable peninsulas: Agrakhansky, Buzachi, Tyub-Karagan, Mangyshlak. Large islands in the northern part of the sea are Tyuleniy and Kulaly. In the deltas of the Volga and Ural rivers, the coastline is complicated by many islands and channels, often changing their position. Many small islands and banks are located on other parts of the coastline.
The middle part of the sea has a relatively flat coastline. On the western coast, on the border with the southern part of the sea, is the Absheron Peninsula. To the east of it there are islands and banks of the Absheron archipelago, of which the largest island is Zhiloy. The eastern coast of the Middle Caspian is more indented; the Kazakh Gulf with Kenderli Bay and several capes stand out here. The largest bay of this coast is Kara-Bogaz-Gol.
South of the Absheron Peninsula are the islands of the Baku archipelago. The origin of these islands, as well as some banks off the eastern coast of the southern part of the sea, is associated with the activity of underwater mud volcanoes lying on the bottom of the sea. On the eastern shore there are large bays of Turkmenbashi and Turkmensky, and near it the island of Ogurchinsky.
One of the most striking phenomena of the Caspian Sea is the periodic variability of its level. In historical times, the Caspian Sea had a level lower than the World Ocean. Fluctuations in the level of the Caspian Sea are so great that for more than a century they have attracted the attention of not only scientists. Its peculiarity is that in the memory of mankind its level has always been below the level of the World Ocean. Since the beginning of instrumental observations (since 1830) of sea level, the amplitude of its fluctuations has been almost 4 m, from –25.3 m in the eighties of the 19th century. to –29 m in 1977. In the last century, the level of the Caspian Sea changed significantly twice. In 1929 it stood at about -26 m, and since it had been close to this level for almost a century, this level position was considered to be a long-term or secular average. In 1930 the level began to decline rapidly. By 1941 it had dropped by almost 2 m. This led to the drying out of vast coastal areas of the bottom. The decrease in level, with slight fluctuations (short-term slight rises in level in 1946–1948 and 1956–1958), continued until 1977 and reached a level of –29.02 m, i.e. the level reached its lowest position in history the last 200 years.
In 1978, contrary to all forecasts, sea level began to rise. As of 1994, the level of the Caspian Sea was at –26.5 m, that is, over 16 years the level rose by more than 2 m. The rate of this rise is 15 cm per year. The level increase in some years was higher, and in 1991 it reached 39 cm.
The general fluctuations in the level of the Caspian Sea are superimposed by its seasonal changes, the long-term average of which reaches 40 cm, as well as surge phenomena. The latter are especially pronounced in the Northern Caspian Sea. The northwestern coast is characterized by large surges created by prevailing storms from the eastern and southeastern directions, especially in the cold season. A number of large (more than 1.5–3 m) surges have been observed here over the past decades. A particularly large surge with catastrophic consequences was noted in 1952. Fluctuations in the level of the Caspian Sea cause great damage to the states surrounding its waters.
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Climate. The Caspian Sea is located in temperate and subtropical climatic zones. Climatic conditions change in the meridional direction, since the sea stretches from north to south for almost 1200 km.
Various atmospheric circulation systems interact in the Caspian region, however, winds from the eastern directions predominate throughout the year (the influence of the Asian High). The position at fairly low latitudes provides a positive balance of heat influx, so the Caspian Sea serves as a source of heat and moisture for passing air masses for most of the year. The average annual air temperature in the northern part of the sea is 8–10°C, in the middle part - 11–14°C, in the southern part - 15–17°C. However, in the northernmost areas of the sea, the average January temperature is from –7 to –10°C, and the minimum during intrusions of Arctic air is down to –30°C, which determines the formation of ice cover. In summer, rather high temperatures dominate over the entire region under consideration - 24–26°C. Thus, the Northern Caspian is subject to the most dramatic temperature fluctuations.
The Caspian Sea is characterized by a very small amount of precipitation per year - only 180 mm, with most of it falling during the cold season of the year (from October to March). However, the Northern Caspian differs in this respect from the rest of the basin: here the average annual precipitation is lower (for the western part only 137 mm), and the seasonal distribution is more uniform (10–18 mm per month). In general, we can talk about the proximity of climatic conditions to arid ones.
Water temperature. The distinctive features of the Caspian Sea (large differences in depths in different parts of the sea, the nature of the bottom topography, isolation) have a certain influence on the formation of temperature conditions. In the shallow Northern Caspian Sea, the entire water column can be considered homogeneous (the same applies to shallow bays located in other parts of the sea). In the Middle and Southern Caspian Sea, surface and deep masses can be distinguished, separated by a transition layer. In the Northern Caspian and in the surface layers of the Middle and Southern Caspian, water temperatures vary over a wide range. In winter, temperatures vary from north to south from less than 2 to 10°C, the water temperature off the west coast is 1–2°C higher than that on the east, in the open sea the temperature is higher than at the coasts: by 2–3°C in the middle part and by 3–4°С in the southern part of the sea. In winter, the distribution of temperature with depth is more uniform, which is facilitated by winter vertical circulation. During moderate and severe winters in the northern part of the sea and shallow bays of the east coast, the water temperature drops to freezing temperature.
In summer, the temperature varies in space from 20 to 28°C. The highest temperatures are observed in the southern part of the sea; temperatures are also quite high in the well-warmed shallow Northern Caspian Sea. The zone where the lowest temperatures occur is adjacent to the east coast. This is explained by the rise of cold deep waters to the surface. Temperatures are also relatively low in the poorly heated deep-sea central part. In open areas of the sea, at the end of May–beginning of June, the formation of a temperature jump layer begins, which is most clearly expressed in August. Most often it is located between horizons of 20 and 30 m in the middle part of the sea and 30 and 40 m in the southern part. In the middle part of the sea, due to the surge off the eastern coast, the shock layer rises close to the surface. In the bottom layers of the sea, the temperature throughout the year is about 4.5°C in the middle part and 5.8–5.9°C in the southern part.
Salinity. Salinity values are determined by such factors as river flow, water dynamics, including mainly wind and gradient currents, the resulting water exchange between the western and eastern parts of the Northern Caspian and between the Northern and Middle Caspian, bottom topography, which determines the location of waters with different salinities, mainly along isobaths, evaporation, providing a deficit of fresh water and an influx of saltier water. These factors collectively influence seasonal differences in salinity.
The Northern Caspian Sea can be considered as a reservoir of constant mixing of river and Caspian waters. The most active mixing occurs in the western part, where both river and Central Caspian waters directly flow. Horizontal salinity gradients can reach 1‰ per 1 km.
The eastern part of the Northern Caspian is characterized by a more uniform salinity field, since most of the river and sea (Middle Caspian) waters enter this area of the sea in a transformed form.
Based on the values of horizontal salinity gradients, it is possible to distinguish in the western part of the Northern Caspian the river-sea contact zone with water salinity from 2 to 10‰, in the eastern part from 2 to 6‰.
Significant vertical salinity gradients in the Northern Caspian are formed as a result of the interaction of river and sea waters, with runoff playing a decisive role. The strengthening of vertical stratification is also facilitated by the unequal thermal state of the water layers, since the temperature of the surface desalinated waters coming from the seashore in summer is 10–15°C higher than the bottom waters.
In the deep-sea depressions of the Middle and Southern Caspian Sea, fluctuations in salinity in the upper layer are 1–1.5‰. The largest difference between the maximum and minimum salinity was noted in the area of the Absheron threshold, where it is 1.6‰ in the surface layer and 2.1‰ at a 5 m horizon.
The decrease in salinity along the western coast of the South Caspian Sea in the 0–20 m layer is caused by the flow of the Kura River. The influence of the Kura runoff decreases with depth; at horizons of 40–70 m, the range of salinity fluctuations is no more than 1.1‰. Along the entire western coast to the Absheron Peninsula there is a strip of desalinated water with a salinity of 10–12.5‰, coming from the Northern Caspian Sea.
In addition, in the Southern Caspian Sea, an increase in salinity occurs when salted waters are carried out from bays and gulfs on the eastern shelf under the influence of southeastern winds. Subsequently, these waters are transferred to the Middle Caspian Sea.
In the deep layers of the Middle and Southern Caspian Sea, the salinity is about 13‰. In the central part of the Middle Caspian, such salinity is observed at horizons below 100 m, and in the deep-water part of the Southern Caspian, the upper boundary of waters with high salinity drops to 250 m. Obviously, in these parts of the sea, vertical mixing of waters is difficult.
Surface water circulation. Currents in the sea are mainly wind-driven. In the western part of the Northern Caspian, currents of the western and eastern quarters are most often observed, in the eastern part - southwestern and southern ones. Currents caused by the runoff of the Volga and Ural rivers can be traced only within the estuary coastal area. The prevailing current speeds are 10–15 cm/s; in open areas of the Northern Caspian Sea, maximum speeds are about 30 cm/s.
In the coastal areas of the middle and southern parts of the sea, in accordance with the wind directions, currents in the northwestern, northern, southeastern and southern directions are observed; near the east coast, currents in the eastern direction often occur. Along the western coast of the middle part of the sea, the most stable currents are southeastern and southern. Current speeds are on average about 20–40 cm/s, with maximum speeds reaching 50–80 cm/s. Other types of currents also play a significant role in the circulation of sea waters: gradient, seiche, and inertial.
Ice formation. The Northern Caspian Sea is covered with ice every year in November, the area of the frozen part of the water area depends on the severity of the winter: in severe winters the entire Northern Caspian Sea is covered with ice, in mild winters the ice remains within 2–3 meter isobath. The appearance of ice in the middle and southern parts of the sea occurs in December-January. On the eastern coast the ice is of local origin, on the western coast it is most often brought from the northern part of the sea. In severe winters, shallow bays freeze off the eastern coast of the middle part of the sea, shores and fast ice form off the coast, and on the western coast, drifting ice spreads to the Absheron Peninsula in abnormally cold winters. The disappearance of ice cover is observed in the second half of February–March.
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Oxygen content. The spatial distribution of dissolved oxygen in the Caspian Sea has a number of patterns. The central part of the waters of the Northern Caspian Sea is characterized by a fairly uniform distribution of oxygen. An increased oxygen content is found in the areas near the Volga River near the mouth, while a decreased oxygen content is found in the southwestern part of the Northern Caspian Sea. In the Middle and Southern Caspian Sea, the highest concentrations of oxygen are confined to shallow coastal areas and pre-estuary coastal areas of rivers, with the exception of the most polluted areas of the sea (Baku Bay, Sumgait region, etc.). In summer, due to the significant warming of water masses and the activation of photosynthesis processes, the leading factors in the formation of the oxygen regime are photosynthetic processes in surface waters, and biochemical oxygen consumption by bottom sediments in bottom waters. Due to the high temperature of the waters, the stratification of the water column, the large influx of organic matter and its intense oxidation, oxygen is quickly consumed with minimal entry into the lower layers of the sea, resulting in the formation of an oxygen deficiency zone in the Northern Caspian Sea. Intense photosynthesis in the open waters of the deep-sea regions of the Middle and Southern Caspian Sea covers the upper 25-meter layer, where oxygen saturation is more than 120%. |
– The Northern Caspian, which is a vast mixing zone of river and sea waters, is characterized by significant spatial gradients in the distribution of nutrients;
– in the Middle Caspian, the cyclonic nature of the circulation contributes to the rise of deep waters with a high content of nutrients into the overlying layers of the sea;
– in the deep-water regions of the Middle and Southern Caspian Sea, the vertical distribution of nutrients depends on the intensity of the convective mixing process, and their content increases with depth.
On the dynamics of concentrations nutrients During the year, the Caspian Sea is influenced by factors such as seasonal fluctuations in biogenic flow into the sea, the seasonal ratio of production-destruction processes, the intensity of exchange between soil and water mass, ice conditions in winter in the Northern Caspian, processes of winter vertical circulation in deep-sea areas seas.
In winter, a significant area of the Northern Caspian Sea is covered with ice, but biochemical processes actively develop in subglacial water and in ice. The ice of the Northern Caspian Sea, being a kind of accumulator of nutrients, transforms these substances entering the sea with river runoff and from the atmosphere.
As a result of the winter vertical circulation of water in the deep-water regions of the Middle and Southern Caspian Sea during the cold season, the active layer of the sea is enriched with nutrients due to their supply from the underlying layers.
Spring for the waters of the Northern Caspian Sea is characterized by a minimum content of phosphates, nitrites and silicon, which is explained by the spring outbreak of phytoplankton development (silicon is actively consumed by diatoms). High concentrations of ammonium and nitrate nitrogen, characteristic of the waters of a large area of the Northern Caspian Sea during floods, are due to intensive washing by river waters of the Volga delta.
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In the spring season, in the area of water exchange between the Northern and Middle Caspian Seas in the subsurface layer, with a maximum oxygen content, the phosphate content is minimal, which, in turn, indicates the activation of the photosynthesis process in this layer.
In the Southern Caspian, the distribution of nutrients in spring is basically similar to their distribution in the Middle Caspian.
In summer, a redistribution of various forms of biogenic compounds is detected in the waters of the Northern Caspian Sea. Here the content of ammonium nitrogen and nitrates decreases significantly, while at the same time there is a slight increase in the concentrations of phosphates and nitrites and a rather significant increase in the concentration of silicon. In the Middle and Southern Caspian Sea, the concentration of phosphates has decreased due to their consumption during photosynthesis and the difficulty of water exchange with the deep-sea accumulation zone.
In autumn in the Caspian Sea, due to the cessation of activity of some types of phytoplankton, the content of phosphates and nitrates increases, and the concentration of silicon decreases, as there is an autumn outbreak of the development of diatoms.
For more than 150 years, oil has been mined on the shelf of the Caspian Sea. oil.
Currently, large hydrocarbon reserves are being developed on the Russian shelf, the resources of which on the Dagestan shelf are estimated at 425 million tons in oil equivalent (of which 132 million tons of oil and 78 billion m3 of gas), on the shelf of the Northern Caspian Sea - at 1 billion tons of oil .
In total, about 2 billion tons of oil have already been produced in the Caspian Sea.
Losses of oil and its products during production, transportation and use reach 2% of the total volume.
Main sources of income pollutants, including petroleum products into the Caspian Sea - this is the removal with river runoff, the discharge of untreated industrial and agricultural wastewater, municipal wastewater from cities and towns located on the coast, shipping, exploration and exploitation of oil and gas fields located at the bottom of the sea, transportation of oil by sea. The places where pollutants enter with river runoff are 90% concentrated in the Northern Caspian Sea, industrial wastes are confined mainly to the area of the Absheron Peninsula, and increased oil pollution of the Southern Caspian Sea is associated with oil production and oil exploration drilling, as well as with active volcanic activity (mud volcanism) in the zone of oil and gas bearing structures.
From the territory of Russia, about 55 thousand tons of petroleum products enter the Northern Caspian annually, including 35 thousand tons (65%) from the Volga River and 130 tons (2.5%) from the runoff of the Terek and Sulak rivers.
Thickening of the film on the water surface to 0.01 mm disrupts gas exchange processes and threatens the death of hydrobiota. The concentration of petroleum products is toxic to fish at 0.01 mg/l and to phytoplankton at 0.1 mg/l.
The development of oil and gas resources on the bottom of the Caspian Sea, the forecast reserves of which are estimated at 12–15 billion tons of standard fuel, will become the main factor in the anthropogenic load on the sea ecosystem in the coming decades.
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Caspian autochthonous fauna. The total number of autochthons is 513 species or 43.8% of the entire fauna, which include herring, gobies, mollusks, etc.
Arctic species. The total number of the Arctic group is 14 species and subspecies, or only 1.2% of the entire Caspian fauna (mysids, sea cockroach, white fish, Caspian salmon, Caspian seal, etc.). The basis of the Arctic fauna are crustaceans (71.4%), which easily tolerate desalination and live at great depths of the Middle and Southern Caspian Sea (from 200 to 700 m), since the lowest water temperatures are maintained here throughout the year (4.9– 5.9°C).
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Mediterranean species. These are 2 types of mollusks, needle fish, etc. At the beginning of the 20s of our century, the mollusk mytileaster entered here, later 2 types of shrimp (with mullet, during their acclimatization), 2 types of mullet and flounder. Some Mediterranean species entered the Caspian Sea after the opening of the Volga-Don Canal. Mediterranean species play a significant role in the food supply of fish in the Caspian Sea.
Freshwater fauna(228 species). This group includes anadromous and semi-anadromous fish (sturgeon, salmon, pike, catfish, carp, and also rotifers).
Marine species. These are ciliates (386 forms), 2 species of foraminifera. There are especially many endemics among higher crustaceans (31 species), gastropods (74 species and subspecies), bivalves (28 species and subspecies) and fish (63 species and subspecies). The abundance of endemics in the Caspian Sea makes it one of the most unique brackish bodies of water on the planet.
The Caspian Sea produces more than 80% of the world's sturgeon catches, the bulk of which occur in the Northern Caspian Sea.
To increase sturgeon catches, which sharply decreased during the years of falling sea levels, a set of measures is being implemented. Among them are a complete ban on sturgeon fishing in the sea and its regulation in rivers, and an increase in the scale of sturgeon factory farming.
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The Caspian Sea is the largest lake on planet Earth. It is called the sea because of its size and bed, which is built like an ocean basin. The area is 371,000 square meters, the depth is 1025 m. The list of rivers flowing into the Caspian Sea includes 130 names. The largest of them are: Volga, Terek, Samur, Sulak, Ural and others.
Caspian Sea
It took 10 million years before the Caspian Sea was formed. The reason for its formation is that the Sarmatian Sea, having lost contact with the World Ocean, was divided into two bodies of water, which were called the Black and Caspian Seas. Between the latter and the World Ocean there are thousands of kilometers of waterless route. It is located at the junction of two continents - Asia and Europe. Its length in the north-south direction is 1200 km, west-east - 195-435 km. The Caspian Sea is an internal endorheic basin of Eurasia.
Near the Caspian Sea, the water level is below the level of the World Ocean, and it is also subject to fluctuations. According to scientists, this is due to many factors: anthropogenic, geological, climatic. Currently, the average water level reaches 28 m.
The river network and wastewater are unevenly distributed along the coast. A few rivers flow into part of the sea from the northern side: Volga, Terek, Ural. From the west - Samur, Sulak, Kura. The east coast is characterized by the absence of permanent watercourses. Differences in space in the flow of water that rivers bring to the Caspian Sea are an important geographical feature of this reservoir.
Volga
This river is one of the largest in Europe. In Russia it ranks sixth in size. In terms of drainage area, it is second only to Siberian rivers flowing into the Caspian Sea, such as the Ob, Lena, Yenisei, and Irtysh. The source from which the Volga begins is taken to be a spring near the village of Volgoverkhovye, Tver Region, on the Valdai Hills. Now at the source there is a chapel that attracts the attention of tourists who are proud to step over the very beginning of the mighty Volga.
A small fast stream gradually gains strength and becomes a huge river. Its length is 3690 km. The source is 225 m above sea level. Among the rivers flowing into the Caspian Sea, the largest is the Volga. Its path runs through many regions of our country: Tver, Moscow, Nizhny Novgorod, Volgograd and others. The territories through which it flows are Tatarstan, Chuvashia, Kalmykia and Mari El. The Volga is the location of millionaire cities - Nizhny Novgorod, Samara, Kazan, Volgograd.
Volga Delta
The main channel of the river is divided into channels. A certain shape of the mouth is formed. It's called delta. Its beginning is the place where the Buzan branch separates from the Volga river bed. The delta is located 46 km north of the city of Astrakhan. It includes channels, branches, and small rivers. There are several main branches, but only Akhtuba is navigable. Among all the rivers of Europe, the Volga has the largest delta, which is a rich fishing region in this basin.
It lies 28 m lower than ocean level. The mouth of the Volga is the location of the southernmost Volga city of Astrakhan, which in the distant past was the capital of the Tatar Khanate. Later, at the beginning of the 18th century (1717), Peter 1 gave the city the status of “capital of the Astrakhan province.” During his reign, the city's main attraction, the Assumption Cathedral, was built. Its Kremlin is made of white stone brought from the capital of the Golden Horde, Saraya. The mouth is divided by branches, the largest of which are: Bolda, Bakhtemir, Buzan. Astrakhan is a southern city located on 11 islands. Today it is a city of shipbuilders, sailors and fishermen.
The Volga currently needs protection. For this purpose, a reserve was established in the place where the river flows into the sea. The delta of the Volga, the largest river flowing into the Caspian Sea, is replete with unique flora and fauna: sturgeon, lotuses, pelicans, flamingos and others. Immediately after the revolution of 1917, a law was passed on their protection by the state as part of the Astrakhan Nature Reserve.
Sulak River
It is located in Dagestan and flows through its territory. It is fed by the waters of melted snow that flow from the mountains, as well as by tributaries: Maly Sulak, Chvakhun-bak, Akh-su. Water also enters Sulak through a canal from the Aksai and Aktash rivers.
The source is formed by the confluence of two rivers that originate in the basins: Didoiskaya and Tushinskaya. The length of the Sulak River is 144 km. Its pool has a fairly large area - 15,200 square meters. It flows through a canyon with the same name as a river, then through the Akhetlinsky gorge and finally reaches the plane. Rounding the Agrakhan Bay from the south, Sulak flows into the sea.
The river provides Kaspiysk and Makhachkala with drinking water, and is home to hydroelectric power stations, the urban-type settlements of Sulak and Dubki, and the small town of Kizilyurt.
Samur
The river received this name not by chance. The name translated from the Caucasian language (one of them) means “middle”. Indeed, the waterway along the Samur River marks the border between the states of Russia and Azerbaijan.
The sources of the river are glaciers and springs originating in the spurs of the Caucasus Range on the northeastern side, not far from Guton Mountain. The height above sea level is 3200 m. Samur has a length of 213 km. The height at the headwaters and the mouth differs by three kilometers. The drainage basin has an area of almost five thousand square meters.
The places where the river flows are narrow gorges located between high mountains made of clayey shales and sandstones, which is why the water here is muddy. The Samur basin has 65 rivers. Their length reaches 10 km or more.
Samur: valley and its description
The valley of this river in Dagestan is the most densely populated area. Near the mouth is Derbent, the oldest city in the world. The banks of the Samur River are home to twenty or more species of relict flora. Endemic, endangered and rare species listed in the Red Book grow here.
In the river delta there is a relict forest, which is the only one in Russia. The liana forest is a fairy tale. Huge trees of the rarest and most common species grow here, intertwined with vines. The river is rich in valuable fish species: mullet, pike perch, pike, catfish and others.
Terek
The river received its name from the Karachay-Balkar peoples who lived along its banks. They called it “Terk Suu”, which means “swift water”. The Ingush and Chechens called it Lomeki - “mountain water”.
The beginning of the river is the territory of Georgia, the Zigla-Khokh glacier is a mountain located on the slope of the Caucasus ridge. It is located under glaciers all year round. One of them melts when sliding down. A small stream is formed, which is the source of the Terek. It is located at an altitude of 2713 m above sea level. The length of the river flowing into the Caspian Sea is 600 km. When it flows into the Caspian Sea, the Terek is divided into many branches, resulting in the formation of a vast delta, its area is 4000 square meters. In some places it is very swampy.
The riverbed in this place changed several times. The old branches have now been converted into canals. The middle of the last century (1957) was marked by the construction of the Kargaly hydroelectric complex. It is used to supply water to the canals.
How is the Terek replenished?
The river has a mixed supply, but for the upper reaches, water from melting glaciers plays an important role; they fill the river. In this regard, 70% of the flow occurs in spring and summer, that is, at this time the water level in the Terek is highest, and the lowest is in February. The river freezes if the winters are characterized by a harsh climate, but the ice cover is unstable.
The river is not clean and transparent. The turbidity of the water is high: 400-500 g/m3. Every year the Terek and its tributaries pollute the Caspian Sea, pouring into it from 9 to 26 million tons of various suspended matter. This is explained by the rocks that make up the shores, which are clayey.
Estuary Terek
The Sunzha is the largest tributary flowing into the Terek, the lower reaches of which are measured from this river. By this time, the Terek flows for a long time through the flat terrain, leaving the mountains located behind the Elkhotov Gate. The bottom here is made of sand and pebbles, the current slows down, and in some places stops altogether.
The mouth of the Terek River has an unusual appearance: the channel here is raised above the valley, in appearance it resembles a canal, which is fenced by a high embankment. The water level becomes higher than the land level. This phenomenon is due to natural causes. Since the Terek is a turbulent river, it brings sand and stones in large quantities from the Caucasus Range. Considering that the current in the lower reaches is weak, some of them settle here and do not reach the sea. For residents of this area, sediment is both a threat and a blessing. When they are washed away by water, floods of great destructive power occur, this is very bad. But in the absence of floods, the soils become fertile.
Ural River
In ancient times (until the second half of the 18th century) the river was called Yaik. It was renamed in the Russian way by decree of Catherine the Second in 1775. Just at this time, the Peasant War, the leader of which was Pugachev, was suppressed. The name has been preserved to this day in the Bashkir language, and is official in Kazakhstan. The Urals are the third longest in Europe; only the Volga and Danube are larger rivers.
The Urals originate in Russia, on the slope of the Round Hill of the Uraltau ridge. The source is a spring gushing out of the ground at an altitude of 637 m above sea level. At the beginning of its journey, the river flows in a north-south direction, but after encountering a plateau along the way, it makes a sharp turn and continues to flow in a north-west direction. However, beyond Orenburg its direction changes again to the southwest, which is considered the main one. Having overcome a winding path, the Urals flows into the Caspian Sea. The length of the river is 2428 km. The mouth is divided into branches and tends to become shallow.
The Ural is a river along which the natural water boundary between Europe and Asia passes, with the exception of the upper reaches. This is an inland European river, but its upper reaches east of the Ural Range are Asian territory.
The importance of the Caspian rivers
The rivers flowing into the Caspian Sea are of great importance. Their waters are used for human and animal consumption, domestic, agricultural and industrial needs. Hydroelectric power stations are built on rivers, the energy of which is in demand by people for various purposes. River basins are full of fish, algae, and shellfish. Even in ancient times, people chose river valleys for future settlements. And now cities and towns are being built on their banks. The rivers are plied by passenger and transport ships, performing important tasks for transporting passengers and cargo.
The Caspian Sea is located on the border of Europe and Asia and is surrounded by the territories of five states: Russia, Azerbaijan, Iran, Turkmenistan and Kazakhstan. Despite its name, the Caspian Sea is the largest lake on the planet (its area is 371,000 km2), but the bottom, composed of oceanic crust, and salty water, together with its large size, give reason to consider it a sea. A large number of rivers flow into the Caspian Sea, for example, such large ones as the Volga, Terek, Ural, Kura and others.
Relief and depth of the Caspian Sea
Based on the bottom topography, the Caspian Sea is divided into three parts: southern (the largest and deepest), middle and northern.
In the northern part, the depth of the sea is the smallest: on average it ranges from four to eight meters, and the maximum depth here reaches 25 m. The northern part of the Caspian Sea is limited by the Mangyshlak Peninsula and occupies 25% of the total area of the reservoir.
The middle part of the Caspian Sea is deeper. Here the average depth becomes 190 m, while the maximum is 788 meters. The area of the middle Caspian Sea is 36% of the total, and the volume of water is 33% of the total volume of the sea. It is separated from the southern part by the Absheron Peninsula in Azerbaijan.
The deepest and largest part of the Caspian Sea is the southern one. It occupies 39% of the total area, and its share of the total water volume is 66%. Here is the South Caspian depression, which contains the deepest point of the sea - 1025 m.
Islands, peninsulas and bays of the Caspian Sea
There are about 50 islands in the Caspian Sea, almost all of them are uninhabited. Due to the shallower depth of the northern part of the sea, most of the islands are located there, among them the Baku archipelago belonging to Azerbaijan, the Tyuleni Islands in Kazakhstan, as well as many Russian islands off the coast of the Astrakhan region and Dagestan.
Among the Caspian Sea peninsulas, the largest are Mangyshlak (Mangistau) in Kazakhstan and Absheron in Azerbaijan, on which such large cities as the capital of the country Baku and Sumgayit are located.
Kara-Bogaz-Gol Bay Caspian Sea
The coastline of the sea is very indented, and there are many bays on it, for example, Kizlyarsky, Mangyshlaksky, Dead Kultuk and others. The Kara-Bogaz-Gol Bay deserves special mention, which is actually a separate lake connected to the Caspian Sea by a narrow strait, thanks to which it maintains a separate ecosystem and higher salinity of water.
Fishing in the Caspian Sea
Since ancient times, the Caspian Sea has attracted residents of its shores with its fish resources. About 90% of the world's sturgeon production is caught here, as well as fish such as carp, bream, and sprat.
Caspian Sea video
In addition to fish, the Caspian Sea is extremely rich in oil and gas, the total reserves of which are about 18-20 million tons. Salt, limestone, sand and clay are also mined here.
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