Caspian lake on the oceans map. Ancient Caspian

The Caspian Sea is the largest closed lake on the planet. This body of water is called the sea for its huge size, brackish water and a regime similar to the sea. The level of the Caspian Sea-lake lies much lower than the level of the World Ocean. At the beginning of 2000, it was around -27 abs. m. At this level, the area of ​​the Caspian Sea is ~ 393 thousand km2 and the volume of water is 78,600 km3. The average and maximum depths are 208 and 1025 m, respectively.

The Caspian Sea stretches from south to north (Fig. 1). The Caspian Sea washes the shores of Russia, Kazakhstan, Turkmenistan, Azerbaijan and Iran. The reservoir is rich in fish, its bottom and shores are rich in oil and gas. The Caspian Sea has been studied quite well, but many mysteries remain in its regime. The most characteristic reservoir - this is an instability of the level with sharp drops and rises. Last promotion level of the Caspian Sea occurred before our eyes from 1978 to 1995. It gave rise to many rumors and speculation. Numerous publications appeared in the press talking about catastrophic floods and an environmental disaster. They often wrote that the rise in the level of the Caspian Sea led to the flooding of almost the entire Volga delta. What is true in the statements made? What is the reason for this behavior of the Caspian Sea?

WHAT HAPPENED TO THE CASPIAN IN THE XX CENTURY

Systematic observations of the level of the Caspian Sea began in 1837. In the second half of the 19th century, the average annual values ​​of the Caspian Sea level were in the range from – 26 to – 25.5 abs. m and had a slight downward trend. This trend continued into the 20th century (Fig. 2). In the period from 1929 to 1941, sea level dropped sharply (by almost 2 m - from - 25.88 to - 27.84 abs. m). In subsequent years, the level continued to fall and, having decreased by approximately 1.2 m, reached in 1977 the lowest level during the observation period - 29.01 abs. m. Then the sea level began to rise rapidly and, having risen by 2.35 m by 1995, reached 26.66 abs. m. In the next four years, the average sea level dropped by almost 30 cm. Its average levels were - 26.80 in 1996, - 26.95 in 1997, - 26.94 in 1998 and - 27.00 abs. m in 1999.

The decrease in sea level in 1930-1970 led to the shallowing of coastal waters, the extension of the coastline towards the sea, and the formation of wide beaches. The latter was perhaps the only positive consequence of the drop in level. There were significantly more negative consequences. As the level dropped, the areas of feeding grounds for fish stocks in the northern Caspian Sea decreased. The shallow-water estuarine coastal area of ​​the Volga began to quickly become overgrown with aquatic vegetation, which worsened the conditions for the passage of fish to spawn in the Volga. Fish catches have sharply decreased, especially valuable species: sturgeon and sterlet. Shipping began to suffer due to the fact that the depths in the approach channels decreased, especially near the Volga delta.

The rise in levels from 1978 to 1995 was not only unexpected, but also led to even greater negative consequences. After all, both the economy and the population of coastal areas have already adapted to the low level.

Many sectors of the economy began to suffer damage. Significant areas were in the flood and flood zone, especially in the northern (plain) part of Dagestan, Kalmykia and the Astrakhan region. The cities of Derbent, Kaspiysk, Makhachkala, Sulak, Kaspiysky (Lagan) and dozens of other smaller settlements suffered from the rise in level. Significant areas of agricultural land are flooded and submerged. Roads, power lines and engineering structures are destroyed industrial enterprises and public services. A threatening situation has developed with fish farming enterprises. Abrasion processes in the coastal zone and the influence of seawater surges have intensified. In recent years, the flora and fauna of the seaside and coastal zone The Volga delta suffered significant damage.

Due to the increase in depth in the shallow waters of the Northern Caspian and the reduction in the areas occupied by aquatic vegetation in these places, the conditions for the reproduction of stocks of anadromous and semi-anadromous fish and the conditions for their migration to the delta for spawning have somewhat improved. However, the predominance negative consequences from rising sea levels has led to talk of an environmental catastrophe. The development of measures to protect national economic facilities and settlements from the advancing sea began.

HOW UNUSUAL IS THE CURRENT BEHAVIOR OF THE CASPIAN SEA?

Research into the life history of the Caspian Sea can help answer this question. Of course, there are no direct observations of the past regime of the Caspian Sea, but there is archaeological, cartographic and other evidence for historical time and the results of paleogeographic studies covering a longer period.

It has been proven that during the Pleistocene (the last 700-500 thousand years), the level of the Caspian Sea underwent large-scale fluctuations in the range of about 200 m: from -140 to + 50 abs. m. During this period of time, four stages are distinguished in the history of the Caspian Sea: Baku, Khazar, Khvalyn and Novo-Caspian (Fig. 3). Each stage included several transgressions and regressions. The Baku transgression occurred 400-500 thousand years ago, sea level rose to 5 abs. m. During the Khazar stage, there were two transgressions: early Khazar (250-300 thousand years ago, maximum level 10 abs. m) and late Khazar (100-200 thousand years ago, highest level -15 abs. m). The Khvalynian stage in the history of the Caspian Sea included two transgressions: the largest during the Pleistocene period, the Early Khvalynian (40-70 thousand years ago, maximum level 47 absolute meters, which is 74 m higher than the modern one) and the Late Khvalynian (10-20 thousand years ago, rise level up to 0 abs. m). These transgressions were separated by the deep Enotayev regression (22-17 thousand years ago), when sea level dropped to -64 abs. m and was 37 m lower than the modern one.

Rice. 4. Fluctuations in the level of the Caspian Sea over the past 10 thousand years. P is the natural range of fluctuations in the level of the Caspian Sea under climatic conditions characteristic of the sub-Atlantic Holocene era (risk zone). I-IV - stages of the New Caspian transgression; M - Mangyshlak, D - Derbent regression

Significant fluctuations in the level of the Caspian Sea also occurred during the New Caspian stage of its history, which coincided with the Holocene (the last 10 thousand years). After the Mangyshlak regression (10 thousand years ago, the level dropped to – 50 abs. m), five stages of the New Caspian transgression were noted, separated by small regressions (Fig. 4). Following fluctuations in sea level—its transgressions and regressions—the outline of the reservoir also changed (Fig. 5).

Over historical time (2000 years), the range of change in the average level of the Caspian Sea was 7 m – from – 32 to – 25 abs. m (see Fig. 4). The minimum level in the last 2000 years was during the Derbent regression (VI-VII centuries AD), when it decreased to – 32 abs. m. During the time elapsed after the Derbent regression, the average sea level changed in an even narrower range - from – 30 to – 25 abs. m. This range of level changes is called the risk zone.

Thus, the level of the Caspian Sea has experienced fluctuations before, and in the past they were more significant than in the 20th century. Such periodic fluctuations are a normal manifestation of the unstable state of a closed reservoir with variable conditions at the outer boundaries. Therefore, there is nothing unusual in the decrease and increase in the level of the Caspian Sea.

Fluctuations in the level of the Caspian Sea in the past, apparently, did not lead to irreversible degradation of its biota. Of course, sharp drops in sea level created temporary unfavorable conditions, for example for fish stocks. However, as the level rose, the situation corrected itself. Natural conditions coastal zone (vegetation, bottom animals, fish) experience periodic changes along with sea level fluctuations and, apparently, have a certain margin of stability and resistance to external influences. After all, the most valuable sturgeon stock has always been in the Caspian basin, regardless of sea level fluctuations, quickly overcoming temporary deterioration in living conditions.

Rumors that rising sea levels caused floods throughout the Volga delta were not confirmed. Moreover, it turned out that the increase in water levels even in the lower part of the delta is inadequate to the magnitude of the rise in sea level. The increase in water level in the lower part of the delta during the low-water period did not exceed 0.2-0.3 m, and during the flood it almost did not appear at all. At the maximum level of the Caspian Sea in 1995, the backwater from the sea extended along the deepest branch of the delta, Bakhtemiru, no more than 90 km, and along other branches no more than 30 km. Therefore, only the islands on the seashore and the narrow coastal strip of the delta were flooded. Flooding in the upper and middle parts of the delta was associated with high floods in 1991 and 1995 (which is a normal phenomenon for the Volga delta) and with the unsatisfactory condition of protective dams. The reason for the weak influence of sea level rise on the regime of the Volga delta is the presence of a huge shallow coastal zone, which dampens the impact of the sea on the delta.

As for the negative impact of sea level rise on the economy and life of the population in the coastal zone, the following should be recalled. At the end of the last century, sea level was higher than it is now, and this was not perceived as ecological catastrophy. And before the level was even higher. Meanwhile, Astrakhan has been known since the middle of the 13th century, and here in the 13th - mid-16th centuries the capital of the Golden Horde, Sarai-Batu, was located. These and many others settlements on the Caspian coast did not suffer from high levels, since they were located on elevated places and during abnormal flood levels or surges, people temporarily moved from low places to higher places.

Why is it that now the consequences of sea level rise, even to lower levels, are perceived as a catastrophe? The reason for the enormous damage caused National economy, is not a rise in level, but a thoughtless and short-sighted development of a strip of land within the mentioned risk zone, freed (as it turned out, temporarily!) from sea level after 1929, that is, when the level dropped below the level of 26 abs. m. The buildings erected in the risk zone, naturally, turned out to be flooded and partially destroyed. Now, when a territory developed and polluted by humans is flooded, a dangerous ecological situation is actually created, the source of which is not natural processes, but unreasonable economic activity.

ABOUT THE REASONS FOR CASPIAN LEVEL FLUCTUATIONS

When considering the reasons for fluctuations in the level of the Caspian Sea, it is necessary to pay attention to the confrontation between two concepts in this area: geological and climatic. Significant contradictions in these approaches emerged, for example, at the international conference "Caspian-95".

According to the geological concept, the causes of changes in the level of the Caspian Sea include processes of two groups. The processes of the first group, according to geologists, lead to changes in the volume of the Caspian basin and, as a consequence, to changes in sea level. Such processes include vertical and horizontal tectonic movements of the earth's crust, accumulation of bottom sediments and seismic phenomena. The second group includes processes that, as geologists believe, affect the underground flow into the sea, either increasing or decreasing it. Such processes are called periodic extrusion or absorption of waters that saturate bottom sediments under the influence of changing tectonic stresses (changes in periods of compression and extension), as well as technogenic destabilization of the subsurface caused by oil and gas production or underground nuclear explosions. It is impossible to deny the fundamental possibility of the influence of geological processes on the morphology and morphometry of the Caspian basin and underground flow. However, at present, the quantitative connection of geological factors with fluctuations in the level of the Caspian Sea has not been proven.

There is no doubt that tectonic movements played a decisive role in the initial stages of the formation of the Caspian basin. However, if we take into account that the Caspian Sea basin is located within a geologically heterogeneous territory, which results in a periodic rather than linear nature of tectonic movements with repeated changes in sign, then one should hardly expect a noticeable change in the capacity of the basin. The tectonic hypothesis is not supported by the fact that the coastlines of the New Caspian transgressions on all sections of the Caspian coast (with the exception of certain areas within the Absheron archipelago) are at the same level.

There is no reason to believe that the cause of fluctuations in the level of the Caspian Sea is a change in the capacity of its depression due to the accumulation of sediments. The rate of filling of the basin with bottom sediments, among which the main role is played by river discharges, is estimated, according to modern data, to be about 1 mm/year or less, which is two orders of magnitude less than the currently observed changes in sea level. Seismic deformations, which are observed only near the epicenter and attenuate at close distances from it, cannot have any significant effect on the volume of the Caspian basin.

As for the periodic large-scale discharge of groundwater into the Caspian Sea, its mechanism is still unclear. At the same time, this hypothesis is contradicted, according to E.G. Maevu, firstly, the undisturbed stratification of silt waters, indicating the absence of noticeable migrations of water through the thickness of bottom sediments, and secondly, the absence of proven powerful hydrological, hydrochemical and sedimentation anomalies in the sea, which should have accompanied large-scale discharge of groundwater that could influence changes in the level of the reservoir.

The main proof of the insignificant role of geological factors at present is the convincing quantitative confirmation of the plausibility of the second, climatic, or more precisely, water-balance concept of Caspian level fluctuations.

CHANGES IN THE COMPONENTS OF THE CASPIAN WATER BALANCE AS THE MAIN REASON FOR FLUCTUATIONS IN ITS LEVEL

For the first time, fluctuations in the level of the Caspian Sea were explained by changes in climatic conditions (more specifically, river flow, evaporation and precipitation on the sea surface) by E.Kh. Lentz (1836) and A.I. Voeikov (1884). Later, the leading role of changes in the components of the water balance in sea level fluctuations was proven again and again by hydrologists, oceanologists, physical geographers and geomorphologists.

The key to most of the studies mentioned is the development of a water balance equation and the analysis of its components. The meaning of this equation is as follows: the change in the volume of water in the sea is the difference between the incoming (river and underground runoff, precipitation on the sea surface) and outgoing (evaporation from the sea surface and outflow of water into the Kara-Bogaz-Gol Bay) components of the water balance. The change in the level of the Caspian Sea is the quotient of the change in the volume of its waters divided by the area of ​​the sea. The analysis showed that the leading role in the water balance of the sea belongs to the ratio of the runoff of the Volga, Ural, Terek, Sulak, Samur, Kura rivers and visible or effective evaporation, the difference between evaporation and precipitation on the sea surface. Analysis of the components of the water balance revealed that the largest contribution (up to 72% of the variance) to the level variability is made by the influx of river water, and more specifically, the zone of runoff formation in the Volga basin. As for the reasons for the change in the Volga runoff itself, many researchers believe that they are associated with the variability of atmospheric precipitation (mainly winter) in the river basin. And the precipitation regime, in turn, is determined by atmospheric circulation. It has long been proven that the latitudinal type of atmospheric circulation contributes to an increase in precipitation in the Volga basin, and the meridional type contributes to a decrease.

V.N. Malinin revealed that the root cause of moisture entering the Volga basin should be sought in the North Atlantic, and specifically in the Norwegian Sea. It is there that an increase in evaporation from the sea surface leads to an increase in the amount of moisture transferred to the continent and, accordingly, to an increase in atmospheric precipitation in the Volga basin. The latest data on the water balance of the Caspian Sea, obtained by employees of the State Oceanographic Institute R.E. Nikonova and V.N. Bortnik, are given with clarifications by the author in table. 1. These data provide convincing evidence that the main causes of both the rapid drop in sea level in the 1930s and the sharp rise in 1978-1995 were changes in river flow, as well as visible evaporation.

Bearing in mind that river flow is one of the main factors influencing the water balance and, as a consequence, the level of the Caspian Sea (and the Volga flow provides at least 80% of the total river flow into the sea and about 70% of the incoming part of the Caspian water balance), It would be interesting to find a connection between sea level and the flow of the Volga alone, measured most accurately. Direct correlation of these quantities does not give satisfactory results.

However, the connection between sea level and Volga runoff is clearly visible if we take into account the river flow not for every year, but take the ordinates of the difference integral runoff curve, that is, the sequential sum of normalized deviations of annual runoff values ​​from the long-term average value (norm). Even a visual comparison of the course of the average annual levels of the Caspian Sea and the difference integral curve of the Volga runoff (see Fig. 2) allows us to identify their similarities.

Over the entire 98-year period of observations of the Volga runoff (the village of Verkhnee Lebyazhye at the top of the delta) and sea level (Makhachkala), the correlation coefficient between the sea level and the ordinates of the difference integral runoff curve was 0.73. If we discard years with small changes in level (1900-1928), then the correlation coefficient increases to 0.85. If we take for analysis a period with a rapid decline (1929-1941) and a rise in level (1978-1995), then the overall correlation coefficient will be 0.987, and separately for both periods 0.990 and 0.979, respectively.

The above calculation results fully confirm the conclusion that during periods of a sharp decrease or rise in sea level, the levels themselves are closely related to the runoff (more precisely, to the sum of its annual deviations from the norm).

A special task is to assess the role of anthropogenic factors in fluctuations in the level of the Caspian Sea, and first of all, the reduction of river flow due to irreversible losses due to the filling of reservoirs, evaporation from the surface of artificial reservoirs, and water intake for irrigation. It is believed that since the 40s, irreversible water consumption has steadily increased, which has led to a reduction in the influx of river water to the Caspian Sea and an additional decrease in its level compared to the natural one. According to V.N. Malinin, by the end of the 80s, the difference between the actual sea level and the restored (natural) reached almost 1.5 m. At the same time, the total irrecoverable water consumption in the Caspian basin was estimated in those years at 36-45 km3/year (of which the Volga accounted for about 26 km3/year). If it were not for the withdrawal of river flow, sea level rise would have begun not in the late 70s, but in the late 50s.

The increase in water consumption in the Caspian basin by 2000 was predicted first to 65 km3/year, and then to 55 km3/year (36 of which were accounted for by the Volga). Such an increase in irrevocable losses of river flow should have reduced the level of the Caspian Sea by more than 0.5 m by 2000. In connection with assessing the impact of irreversible water consumption on the level of the Caspian Sea, we note the following. Firstly, estimates in the literature of the volumes of water intake and losses due to evaporation from the surface of reservoirs in the Volga basin are apparently significantly overestimated. Secondly, forecasts for the growth of water consumption turned out to be erroneous. The forecasts included the pace of development of water-consuming sectors of the economy (especially irrigation), which not only turned out to be unrealistic, but also gave way to a decline in production in recent years. In fact, as A.E. points out. Asarin (1997), by 1990, water consumption in the Caspian basin was about 40 km3/year, and has now decreased to 30-35 km3/year (in the Volga basin up to 24 km3/year). Therefore, the “anthropogenic” difference between the natural and actual sea level is currently not as great as predicted.

ABOUT POSSIBLE FLUCTUATIONS IN THE CASPIAN SEA LEVEL IN THE FUTURE

The author does not set himself the goal of analyzing in detail the numerous forecasts of fluctuations in the level of the Caspian Sea (this is an independent and difficult task). The main conclusion from assessing the results of forecasting Caspian level fluctuations can be drawn as follows. Although the forecasts were based on completely different approaches (both deterministic and probabilistic), there was not a single reliable forecast. The main difficulty in using deterministic forecasts based on the sea water balance equation is the lack of development of the theory and practice of ultra-long-term climate change forecasts over large areas.

When sea levels dropped in the 1930s to 1970s, most researchers predicted they would fall further. In the last two decades, when sea level rise began, most forecasts predicted an almost linear and even accelerating rise in sea level to -25 and even -20 abs. m and higher at the beginning of the 21st century. Three circumstances were not taken into account. Firstly, the periodic nature of fluctuations in the level of all closed reservoirs. The instability of the Caspian Sea level and its periodic nature is confirmed by an analysis of its current and past fluctuations. Secondly, at a sea level close to – 26 abs. m, the flooding of large bays-sors on the north-eastern coast of the Caspian Sea - Dead Kultuk and Kaydak, as well as low-lying areas in other places on the coast - will begin to flood, which have dried out at low levels. This would lead to an increase in the area of ​​shallow waters and, as a consequence, to an increase in evaporation (up to 10 km3/year). At a higher sea level, the outflow of water into Kara-Bogaz-Gol will increase. All this should stabilize or at least slow down the level increase. Thirdly, level fluctuations under the conditions of the modern climatic era (the last 2000 years), as shown above, are limited by the risk zone (from – 30 to – 25 abs. m). Taking into account the anthropogenic decrease in runoff, the level is unlikely to exceed the level of 26-26.5 abs. m.

The decrease in average annual levels in the last four years by a total of 0.34 m may indicate that in 1995 the level reached its maximum (- 26.66 abs. m), and a change in the trend of the Caspian level. In any case, the prediction is that sea level is unlikely to exceed 26 absolute. m, apparently, is justified.

In the 20th century, the level of the Caspian Sea changed within 3.5 m, first falling and then rising sharply. This behavior of the Caspian Sea is the normal state of a closed reservoir as an open dynamic system with variable conditions at its inlet.

Each combination of incoming (river flow, precipitation on the sea surface) and outgoing (evaporation from the surface of a reservoir, outflow into the Kara-Bogaz-Gol Bay) components of the Caspian water balance corresponds to its own level of equilibrium. Since the components of the water balance of the sea also change under the influence of climatic conditions, the level of the reservoir fluctuates, trying to reach an equilibrium state, but never reaches it. Ultimately, the trend of changes in the level of the Caspian Sea at a given time depends on the ratio of precipitation minus evaporation in the catchment area (in the basins of the rivers that feed it) and evaporation minus precipitation above the reservoir itself. There is actually nothing unusual about the recent rise in the Caspian sea level by 2.3 m. Such level changes have happened many times in the past and have not caused irreparable damage to the natural resources of the Caspian Sea. The current rise in sea level has become a catastrophe for the economy coastal zone only because of man’s unreasonable exploration of this risk zone.

Vadim Nikolaevich Mikhailov, Doctor of Geographical Sciences, Professor of the Department of Land Hydrology, Faculty of Geography, Moscow State University, Honored Scientist of the Russian Federation, Full Member of the Academy of Water Sciences. Area of ​​scientific interests: hydrology and water resources, interaction of rivers and seas, deltas and estuaries, hydroecology. Author and co-author of about 250 scientific works, including 11 monographs, two textbooks, four scientific and methodological manuals.

Caspian Sea

The Caspian Sea is the largest lake on Earth, located at the junction of Europe and Asia, called a sea because of its size. The Caspian Sea is an endorheic lake, and the water in it is salty, from 0.05% near the mouth of the Volga to 11-13% in the southeast. The water level is subject to fluctuations, currently approximately 28 m below sea level. The area of ​​the Caspian Sea is currently approximately 371,000 km2, maximum depth is 1025 m.

The length of the coastline of the Caspian Sea is estimated at approximately 6500 - 6700 kilometers, with islands - up to 7000 kilometers. The shores of the Caspian Sea in most of its territory are low-lying and smooth. In the northern part, the coastline is indented by water channels and islands of the Volga and Ural deltas, the banks are low and swampy, and the water surface in many places is covered with thickets. The east coast is dominated by limestone shores adjacent to semi-deserts and deserts. The most winding shores are on the western coast in the area of ​​the Absheron Peninsula and on the eastern coast in the area of ​​the Kazakh Gulf and Kara-Bogaz-Gol.

130 rivers flow into the Caspian Sea, of which 9 rivers have a delta-shaped mouth. Large rivers flowing into the Caspian Sea are the Volga, Terek (Russia), Ural, Emba (Kazakhstan), Kura (Azerbaijan), Samur (Russian border with Azerbaijan), Atrek (Turkmenistan) and others.

The Caspian Sea washes the shores of five coastal states:

Russia (Dagestan, Kalmykia and Astrakhan region) - in the west and northwest, coastline length 695 kilometers Kazakhstan - in the north, northeast and east, coastline length 2320 kilometers Turkmenistan - in the southeast, coastline length 1200 kilometers Iran - in the south, coastline length - 724 kilometers Azerbaijan - in the southwest, coastline length 955 kilometers

Water temperature

Subject to significant latitudinal changes, most clearly expressed in winter period, when the temperature changes from 0 - 0.5 °C at the ice edge in the north of the sea to 10 - 11 °C in the south, that is, the water temperature difference is about 10 °C. For shallow water areas with depths less than 25 m, the annual amplitude can reach 25 - 26 °C. On average, the water temperature off the west coast is 1 - 2 °C higher than that on the east, and in the open sea the water temperature is 2 - 4 °C higher than on the coasts.

The climate of the Caspian Sea is continental in the northern part, temperate in the middle and subtropical in the southern part. In winter, the average monthly temperature of the Caspian Sea varies from?8?10 in the northern part to +8 - +10 in the southern part, in summer - from +24 - +25 in the northern part to +26 - +27 in the southern part. The maximum temperature recorded on the east coast was 44 degrees.

Animal world

The fauna of the Caspian Sea is represented by 1809 species, of which 415 are vertebrates. 101 species of fish are registered in the Caspian Sea, where most of the world's sturgeon stocks are concentrated, as well as freshwater fish such as roach, carp, and pike perch. The Caspian Sea is the habitat of fish such as carp, mullet, sprat, kutum, bream, salmon, perch, and pike. The Caspian Sea is also home to a marine mammal - the Caspian seal.

Vegetable world

The flora of the Caspian Sea and its coast is represented by 728 species. Among the plants in the Caspian Sea, the predominant algae are blue-green, diatoms, red, brown, characeae and others, and among the flowering plants - zoster and ruppia. In origin, the flora is predominantly of Neogene age, but some plants were brought into the Caspian Sea by humans deliberately or on the bottoms of ships.

Mining of oil and gas

Many oil and gas fields are being developed in the Caspian Sea. Proven oil resources in the Caspian Sea amount to about 10 billion tons, total oil and gas condensate resources are estimated at 18 - 20 billion tons.

Oil production in the Caspian Sea began in 1820, when the first oil well was drilled on the Absheron shelf. In the second half of the 19th century, oil production began on an industrial scale on the Absheron Peninsula, and then in other territories.

In addition to oil and gas production, salt, limestone, stone, sand, and clay are also mined on the coast of the Caspian Sea and the Caspian shelf.

Not all of the countries located on the shores of the Caspian Sea can be listed.

Countries on the Caspian Sea

Caspian Sea is the largest inland body of water on our planet by area. It also has no churn. The Caspian Sea is classified in different ways: as the world's largest lake and as a full-fledged sea. Its surface area is 371,000 km 2 (143,200 mi 2) and its volume is 78,200 km 3. Maximum depth 1025 m. Sea salinity is about 1.2% (12 g/l). The water level in the sea constantly fluctuates due to tectonic movements and high air temperatures. Today it is 28 m below sea level.

Even the ancient inhabitants who inhabited the coast of the Caspian Sea perceived it as a real ocean. It seemed to them limitless and very large. The word “Caspian” comes from the language of these peoples.

What countries are located on the shores of the Caspian Sea?

Sea waters wash the shores of 5 coastal states. This:

• Russia. The coastal zone covers Kalmykia, Dagestan and the Astrakhan region in the northwest and west. The length of the coastline is 695 km.
• Kazakhstan. The coastal zone covers the east, north and northeast of the state. The length of the coastline is 2320 km.
• Turkmenistan. The coastal zone covers the southeast of the country. The length of the coastline is 1200 km.
• Iran. The coastal zone covers the southern part of the state. The length of the coastline is 724 km.
• Azerbaijan. The coastal zone covers the southwest of the country. The length of the coastline is 955 km.

In addition, this water volume is the main object International Society, since there are huge reserves here natural gas and oil. The Caspian Sea is only 700 miles long, but it contains six basins with hydrocarbon reserves. Most of them have not been mastered by humans.

The Caspian Sea is located on the continent of Eurasia. The surprising thing is that the Caspian Sea, with an area of ​​370 thousand square kilometers, is actually the largest lake, since it has no connection with the ocean. Although it is difficult to call it a lake, because the composition of the water, flora and fauna are similar to those of the sea. The salinity of the water is close to oceanic (from 0.05% to 13%).

Photo: Seagulls on the shores of the Caspian Sea.

About 50 million years ago in the territory of Eastern Europe The Tethys Sea was located, which dried up and divided into several large bodies of water - the Caspian, Black and Mediterranean seas.

Thanks to mineral waters and the healing mud of the Caspian Sea has great recreational and health potential. Therefore, there is an increase in the popularity of the coasts of Turkmenistan, Iran, Azerbaijan and Russian Dagestan among tourists.

Particularly popular is the resort area in the Baku region, where the popular resort in Amburan is located, as well as the area of ​​​​the village of Nardaran, sanatoriums in the villages of Zagulba and Bilgah. In the north of Azerbaijan, the resort in Nabran is gaining popularity.

Unfortunately, tourism in Turkmenistan is poorly developed, which is due to the policy of isolation. And in Iran, Sharia law prohibits foreign tourists from vacationing on the coast.

But if you decide to relax on the Caspian Lake, then you will enjoy walking through protected areas; you will see extraordinary floating islands, various plants and animals that live in fresh and salt waters.

There is a greater variety of ways to have a good time throughout the year. For example, you can go on boat cruises, go fishing or waterfowl hunting, or you can simply enjoy the healing waters, looking at seals and a variety of birds. The protected areas of the sea coast are very beautiful, for example the Astrakhan International Biosphere Reserve and the Volga delta with lotus fields.

A special feature of the Caspian zone is the oriental flavor with hookah and mesmerizing dances. Traditional music will delight your ears, and East Asian cuisine will satisfy your hunger.

See where the Caspian Sea is located on the world map.

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Video: Caspian Sea. Storm. 07/08/2012.

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 area of ​​the sea 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. Average depth this part of the sea is 190 m, the largest 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 seabed. 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.

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. Distinctive features Caspian Sea (large differences in depths in various parts seas, 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 factors such 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 Sea 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.

– 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
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.

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.

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).

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.