Today in Astrakhan the program for celebrating Caspian Sea Day began. Such holidays are also celebrated in the five Caspian states. Although the Caspian Sea requires in modern conditions not so much festive events, but respect from all who inhabit its shores and exploit its wealth.
“Caspian News”, of course, cannot stand aside, because the attitude towards the Caspian Sea is inherent in the very name and ideology of our portal. Our story about a unique reservoir is a kind of offering to the “hero of the occasion.”
The uniqueness of the Caspian Sea lies, first of all, in the fact that it is not a sea, but a real endorheic lake. The sea must have access to the World Ocean, which the Caspian does not have; on the other hand, this salty lake has all the signs of the sea, from ebbs and flows to real storms, about which sailors say: “No ocean storms are scary for someone who has survived a storm in the Caspian.” " And the oceanic bottom topography is convincing evidence that initially the Caspian Sea, together with the Black and Azov Seas, belonged to a single ancient body of water, that is, it was part of the World Ocean.
Where the Caspian Lake is now located, several tens of thousands of years ago a depression was formed in the earth’s crust. Today it is filled with the waters of the Caspian Sea. At the end of the 20th century, the water level in the Caspian Sea was 28 meters below the level of the World Ocean. About six thousand years ago, the waters of the Caspian Sea gained independence, parting with the World Ocean. Another feature that distinguishes the Caspian from the sea is that the salinity of the water in it is almost three times lower than the salinity of the sea. This is because the rivers carry their fresh water to the Caspian Sea. The Volga accounts for the largest contribution: it gives almost 80% of all water to the sea-lake. And it also connects the Caspian Sea with the World Ocean through a system of canals. That's why this lake is still considered a sea!
In terms of its area and volume of water, the Caspian Sea-lake has no equal on Earth. The volume of water in the Caspian Sea accounts for 44% of the reserve of all lake waters on the planet! If we talk about the depth of reservoirs, their area and volume of water, the lake can compete with the Yellow, Baltic and Black Seas and surpasses the Aegean and Adriatic Seas in these same parameters.
Not every sea can boast that during its history it has had as many names as the Caspian: as many as seventy! Every traveler, every expedition to the Caspian Sea and the ancient peoples inhabiting its coast gave it their names. The most famous names are: Djurdzhansky, Khvalynsky, Shirvansky, Derbentsky, Saraysky and finally, Khazar. In Azerbaijan and Iran, the Caspian Sea is still called the Khazar Sea. And the sea received its modern name because of the tribes of Caspian horse breeders, who for a very long time inhabited the eastern parts of the Caucasus and the steppes of the Caspian territories.
The Caspian Sea is the hero of many legends and traditions in the epic of all peoples living on its shores. Legends, as a rule, tell about the love of a mighty and handsome Caspian hero for one of the beauties named Volga, Kura or Amu Darya - the choice is huge, since about 130 large and small rivers flow into the sea, nine of which have a mouth in the form deltas. Everyone's fantasy on the theme of love is approximately the same.
The sea area is divided into three regions: Northern, Middle and Southern Caspian. The Northern Caspian is shallow. The greatest depth of the Middle Caspian in the area of the Derbent depression is about 788 m. Beyond the Absheron threshold the South Caspian begins, this is where the sea is deepest: about 1025 m. For clarity, imagine three Eiffel towers stacked on top of each other.
There are many secrets and mysteries associated with the Caspian Sea. In 1939, archaeological divers found a flooded ancient guest house (caravanserai) in Baku Bay. Many inscriptions have been preserved on the walls, indicating that the building was erected in 1234-1235. Perhaps these are the remains of the ancient city of Sabail. Ancient quarries have been discovered nearby in the sea. And in 1940, during the construction of a dam on the Absheron Peninsula, an ancient cemetery was discovered at the bottom of the sea. The burials date back to the 1st century BC. It can be assumed that the level of the Caspian Sea in those days was about four meters lower than today.
It is no coincidence that the inscription on a geographical map drawn up in 1320 reads: “The sea rises every year to one hand, and many good cities are already flooded.”
Instrumental measurements of the level of the Caspian Sea and systematic observations of its fluctuations have been carried out since 1837. The highest water level was recorded in 1882 (−25.2 m), the lowest in 1977 (−29.0 m), since 1978 the water level has risen and in 1995 reached −26.7 m, since 1996 year began to decline again, and since 2001 - to rise again and reached a level of −26.3 m. The reasons for this “behavior” of the Caspian Sea are climate change, as well as geological and anthropogenic factors.
The Caspian seal remains another mystery of the unique sea-lake: scientists cannot answer the question of where the animal of northern latitudes came from in the Caspian Sea. In total, 1809 species of different groups of animals live in the Caspian Sea. The Caspian Sea is also famous for its valuable fish species, in particular sturgeon. Their reserves account for up to 80% of the world's resources. The most valuable caviar is not black, as many are accustomed to believe, but white. Albino Beluga caviar ranges in color from light gray to white. The lighter, the more expensive: the cost of 100 grams is $2,000. This fish is caught in the Caspian Sea off the coast of Iran.
Many oil and gas fields are being developed in the Caspian Sea. The first oil well was drilled on the Absheron Peninsula near Baku back in 1820. In 1949, they began to extract oil from the bottom of the Caspian Sea for the first time. Salt, limestone, stone, sand and clay are also mined on the coast of the Caspian Sea and the Caspian shelf.
The Caspian Sea washes the shores of five countries: Kazakhstan, Azerbaijan, Turkmenistan, Iran and Russia. Caspian Day has been celebrated in every country for several years now, reminding that the Caspian Sea is not just a waterer and breadwinner for the peoples inhabiting its shores, but a very fragile ecosystem.
By the way, in 1978, World Maritime Day appeared on the calendar of world events, which refers to the international UN days, designed to draw humanity’s attention to the problems of the hydraulic system. There is also an International Black Sea Day: in 1996, representatives of Russia, Ukraine, Bulgaria, Romania, Turkey and Georgia signed a strategic action plan to save the Black Sea. In this regard, the Day of the Caspian Sea is also, rather, not a holiday, but a warning, a warning to people about how everything is interconnected in this world and how it is possible, by mercilessly exploiting, to lose what is dear to everyone.
Marina Parenskaya
Caspian SeaThe Caspian Sea is one of the most amazing closed bodies of water on Earth.
Over the centuries, the sea has changed more than 70 names. The modern one came from the Caspians - tribes inhabiting the central and southeastern part of Transcaucasia 2 thousand years BC.
Geography of the Caspian Sea
The Caspian Sea is located at the junction of Europe and Asia and, according to its geographical location, is divided into the South, North and Middle Caspian.
The middle and northern part of the sea belongs to Russia, the southern to Iran, the eastern to Turkmenistan and Kazakhstan, and the southwestern to Azerbaijan.
For many years, the Caspian states have been dividing the Caspian waters among themselves, and quite sharply at that.
Caspian sea map
Lake or sea?
In fact, the Caspian Sea is the world's largest lake, but has a number of marine signs.
These include: a large body of water, strong storms with high waves, high and low tides.
But the Caspian Sea does not have a natural connection with the World Ocean, which makes it impossible to call it a sea.
At the same time, thanks to the Volga and artificially created channels, such a connection appeared.
The salinity of the Caspian Sea is 3 times lower than the usual sea salinity, which does not allow the reservoir to be classified as a sea.
There were times when the Caspian Sea was truly part of the World Ocean.
Several tens of thousands of years ago the Caspian Sea was connected to the Sea of Azov, and through it to the Black and Mediterranean.
As a result of long-term processes occurring in the earth's crust, the Caucasus Mountains were formed, which isolated the reservoir.
The connection between the Caspian and Black Seas was carried out for a long time through the strait (Kuma-Manych depression) and gradually ceased.
Physical quantities
Area, volume, depth
The area, volume and depth of the Caspian Sea are not constant and directly depend on the water level.
On average, the area of the reservoir is 371,000 km², the volume is 78,648 km³ (44% of all world lake water reserves).
The depth of the Caspian Sea in comparison with lakes Baikal and Tanganyika
The average depth of the Caspian Sea is 208 m; the northern part of the sea is considered the shallowest. The maximum depth is 1025 m, noted in the South Caspian depression.
In terms of depth, the Caspian Sea is second only to Baikal and Tanganyika.
The length of the lake from north to south is about 1200 km, from west to east on average 315 km. The length of the coastline is 6600 km, with islands - about 7 thousand km.
Shores
Mostly, the coast of the Caspian Sea is low and smooth.
In the northern part- strongly indented by the river channels of the Urals and Volga. The swampy shores here are located very low.
Eastern Shores adjacent to semi-desert zones and deserts, covered with limestone deposits.
The most winding shores are in the west in the area of the Absheron Peninsula, and in the east in the area of the Kazakh Bay and Kara-Bogaz-Gol.
Sea water temperature
Temperature of the Caspian Sea at different times of the year
Average water temperature in winter in the Caspian Sea it ranges from 0 °C in the northern part to +10 °C in the southern part.
In Iranian waters, the temperature does not drop below +13 °C.
With the onset of cold weather, the shallow northern part of the lake is covered with ice, which lasts for 2-3 months. The thickness of the ice cover is 25-60 cm, at especially low temperatures it can reach 130 cm. In late autumn and winter, drifting ice floes can be observed in the north.
Average temperature in summer The surface water temperature in the sea is + 24 °C.
In most parts the sea warms up to +25 °C…+30 °C.
Warm water and beautiful sandy, occasionally shell and pebble beaches create excellent conditions for a good beach holiday.
In the eastern part of the Caspian Sea, near the city of Begdash, it remains abnormally low water temperature.
Nature of the Caspian Sea
Islands, peninsulas, bays, rivers
The Caspian Sea includes about 50 large and medium-sized islands, with a total area of 350 km².
The largest of them are: Ashur-Ada, Garasu, Gum, Dash and Boyuk-Zira. The largest peninsulas are: Agrakhansky, Absheronsky, Buzachi, Mangyshlak, Miankale and Tyub-Karagan.
Tyuleniy Island in the Caspian Sea, part of the Dagestan Nature Reserve
To the largest bays of the Caspian Sea include: Agrakhansky, Kazakh, Kizlyarsky, Dead Kultuk and Mangyshlaksky.
In the east is salt lake Kara-Bogaz-Gol, formerly a lagoon connected to the sea by a strait.
In 1980, a dam was built on it, through which water from the Caspian goes to Kara-Bogaz-Gol, where it then evaporates.
130 rivers flow into the Caspian Sea, located mainly in its northern part. The largest of them are: Volga, Terek, Sulak, Samur and Ural.
The average annual drainage of the Volga is 220 km³. 9 rivers have delta-shaped mouths.
Flora and fauna
The Caspian Sea is home to about 450 species of phytoplankton, including algae, aquatic and flowering plants. Of the 400 species of invertebrates, worms, crustaceans and molluscs predominate. There are a lot of small shrimp in the sea, which are the object of fishing.
More than 120 species of fish live in the Caspian Sea and delta. Fishing objects include sprat (“Kilkin fleet”), catfish, pike, bream, pike perch, kutum, mullet, roach, rudd, herring, white fish, pike perch, goby, grass carp, burbot, asp and pike perch. Stocks of sturgeon and salmon are currently depleted, however, the sea is the largest supplier of black caviar in the world.
Fishing in the Caspian Sea is allowed all year round, with the exception of the period from late April to late June. There are many fishing bases with all amenities on the coast. Fishing in the Caspian Sea is a great pleasure. In any part of it, including in large cities, the catch is unusually rich.
The lake is famous for its wide variety of waterfowl. Geese, ducks, loons, gulls, waders, eagles, geese, swans and many others fly to the Caspian Sea during the migration or nesting period.
The largest number of birds - over 600 thousand individuals - is observed at the mouths of the Volga and Ural, in the Turkmenbashi and Kyzylagach bays. During the hunting season, a huge number of fishermen come here not only from Russia, but also from countries near and far abroad.
Caspian seal
The Caspian Sea is home to the only mammal. This is the Caspian seal or seal. Until recently, seals swam close to the beaches, everyone could admire the amazing animal with round black eyes, and the seals behaved very friendly.
Now the seal is on the verge of extinction.
Cities on the Caspian Sea
The largest city on the Caspian Sea coast is Baku.
The population of one of the most beautiful cities in the world is over 2.5 million people. Baku is located on the picturesque Absheron Peninsula and is surrounded on three sides by the waters of the warm and oil-rich Caspian Sea.
Smaller cities: the capital of Dagestan is Makhachkala, the Kazakh Aktau, the Turkmen Turkmenbashi and the Iranian Bender-Anzeli.
Baku Bay, Baku - a city on the Caspian Sea
Interesting Facts
Scientists are still arguing about whether to call a body of water a sea or a lake.
The level of the Caspian Sea is gradually decreasing.
The Volga delivers most of the water to the Caspian Sea.
90% of black caviar is mined in the Caspian Sea. Among them, the most expensive is the albino beluga caviar “Almas” ($2 thousand per 100 g).
Companies from 21 countries are taking part in the development of oil fields in the Caspian Sea. According to Russian estimates, hydrocarbon reserves in the sea amount to 12 billion tons.
American scientists claim that a fifth of the world's hydrocarbon reserves are concentrated in the depths of the Caspian Sea. This is more than the combined reserves of oil-producing countries such as Kuwait and Iraq.
, Kazakhstan, Turkmenistan, Iran, Azerbaijan
Geographical position
Caspian Sea - view from space.
The Caspian Sea is located at the junction of two parts of the Eurasian continent - Europe and Asia. The length of the Caspian Sea from north to south is approximately 1200 kilometers (36°34"-47°13" N), from west to east - from 195 to 435 kilometers, on average 310-320 kilometers (46°-56° v. d.).
The Caspian Sea is conventionally divided according to physical and geographical conditions into 3 parts - Northern Caspian, Middle Caspian and Southern Caspian. The conditional border between the Northern and Middle Caspian runs along the line of the island. Chechen - Cape Tyub-Karagansky, between the Middle and Southern Caspian Sea - along the line of the island. Residential - Cape Gan-Gulu. The area of the Northern, Middle and Southern Caspian Sea is 25, 36, 39 percent, respectively.
Coast of the Caspian Sea
Coast of the Caspian Sea in Turkmenistan
The territory adjacent to the Caspian Sea is called the Caspian region.
Peninsulas of the Caspian Sea
- Ashur-Ada
- Garasu
- Zyanbil
- Khara-Zira
- Sengi-Mugan
- Chygyl
Bays of the Caspian Sea
- Russia (Dagestan, Kalmykia and Astrakhan region) - in the west and northwest, the length of the coastline is about 1930 kilometers
- Kazakhstan - in the north, northeast and east, the length of the coastline is about 2320 kilometers
- Turkmenistan - in the southeast, the length of the coastline is about 650 kilometers
- Iran - in the south, the length of the coastline is about 1000 kilometers
- Azerbaijan - in the southwest, the length of the coastline is about 800 kilometers
Cities on the Caspian Sea coast
On the Russian coast are the cities of Lagan, Makhachkala, Kaspiysk, Izberbash and the southernmost city of Russia, Derbent. Astrakhan is also considered a port city of the Caspian Sea, which, however, is not located on the shores of the Caspian Sea, but in the Volga delta, 60 kilometers from the northern coast of the Caspian Sea.
Physiography
Area, depth, volume of water
The area and volume of water in the Caspian Sea varies significantly depending on fluctuations in water levels. At a water level of −26.75 m, the area is approximately 371,000 square kilometers, the volume of water is 78,648 cubic kilometers, which is approximately 44% of the world's lake water reserves. The maximum depth of the Caspian Sea is in the South Caspian depression, 1025 meters from its surface level. In terms of maximum depth, the Caspian Sea is second only to Baikal (1620 m) and Tanganyika (1435 m). The average depth of the Caspian Sea, calculated from the bathygraphic curve, is 208 meters. At the same time, the northern part of the Caspian Sea is shallow, its maximum depth does not exceed 25 meters, and the average depth is 4 meters.
Water level fluctuations
Vegetable world
The flora of the Caspian Sea and its coast is represented by 728 species. The predominant plants in the Caspian Sea are algae - blue-green, diatoms, red, brown, characeae and others, and 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.
History of the Caspian Sea
Origin of the Caspian Sea
Anthropological and cultural history of the Caspian Sea
Finds in the Khuto Cave off the southern coast of the Caspian Sea indicate that man lived in these areas approximately 75 thousand years ago. The first mentions of the Caspian Sea and the tribes living on its coast are found in Herodotus. Around the V-II centuries. BC e. Saka tribes lived on the Caspian coast. Later, during the period of settlement of the Turks, in the period of the 4th-5th centuries. n. e. Talysh tribes (Talysh) lived here. According to ancient Armenian and Iranian manuscripts, Russians sailed the Caspian Sea from the 9th-10th centuries.
Research of the Caspian Sea
Research of the Caspian Sea was started by Peter the Great, when, on his order, an expedition was organized in 1714-1715 under the leadership of A. Bekovich-Cherkassky. In the 1720s, hydrographic research was continued by the expedition of Karl von Werden and F. I. Soimonov, and later by I. V. Tokmachev, M. I. Voinovich and other researchers. At the beginning of the 19th century, instrumental surveys of the shores were carried out by I. F. Kolodkin, in the mid-19th century. - instrumental geographical survey under the direction of N. A. Ivashintsev. Since 1866, for more than 50 years, expeditionary research on the hydrology and hydrobiology of the Caspian Sea was carried out under the leadership of N. M. Knipovich. In 1897, the Astrakhan Research Station was founded. In the first decades of Soviet power, geological research by I.M. Gubkin and other Soviet geologists was actively carried out in the Caspian Sea, mainly aimed at searching for oil, as well as research into the study of water balance and level fluctuations in the Caspian Sea.
Economy of the Caspian Sea
Mining of oil and gas
Many oil and gas fields are being developed in the Caspian Sea. Proven oil resources in the Caspian Sea are 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 near Baku. In the second half of the 19th century, oil production began on an industrial scale on the Absheron Peninsula, and then in other territories.
Shipping
Shipping is developed in the Caspian Sea. There are ferry crossings on the Caspian Sea, in particular, Baku - Turkmenbashi, Baku - Aktau, Makhachkala - Aktau. The Caspian Sea has a shipping connection with the Sea of Azov through the Volga, Don and Volga-Don Canal rivers.
Fishing and seafood production
Fishing (sturgeon, bream, carp, pike perch, sprat), caviar production, as well as seal fishing. More than 90 percent of the world's sturgeon catch occurs in the Caspian Sea. In addition to industrial mining, illegal fishing of sturgeon and their caviar flourishes in the Caspian Sea.
Recreational resources
The natural environment of the Caspian coast with sandy beaches, mineral waters and healing mud in the coastal zone creates good conditions for recreation and treatment. At the same time, in terms of the degree of development of resorts and the tourism industry, the Caspian coast is noticeably inferior to the Black Sea coast of the Caucasus. At the same time, in recent years, the tourism industry has been actively developing on the coasts of Azerbaijan, Iran, Turkmenistan and Russian Dagestan. In Azerbaijan, the resort area in the Baku region is actively developing. At the moment, a world-class resort has been created in Amburan, another modern tourist complex is being built in the area of the village of Nardaran, and holidays in the sanatoriums of the villages of Bilgah and Zagulba are very popular. A resort area is also being developed in Nabran, in northern Azerbaijan. However, high prices, a generally low level of service and a lack of advertising lead to the fact that there are almost no foreign tourists at the Caspian resorts. The development of the tourism industry in Turkmenistan is hampered by a long-term policy of isolation, in Iran - Sharia laws, due to which mass holidays of foreign tourists on the Caspian coast of Iran are impossible.
Ecological problems
Environmental problems of the Caspian Sea are associated with water pollution as a result of oil production and transportation on the continental shelf, the flow of pollutants from the Volga and other rivers flowing into the Caspian Sea, the life activity of coastal cities, as well as the flooding of individual objects due to rising levels of the Caspian Sea. Predatory production of sturgeon and their caviar, rampant poaching lead to a decrease in the number of sturgeon and to forced restrictions on their production and export.
International status of the Caspian Sea
Legal status of the Caspian Sea
After the collapse of the USSR, the division of the Caspian Sea has long been and still remains the subject of unresolved disagreements related to the division of Caspian shelf resources - oil and gas, as well as biological resources. For a long time, negotiations were ongoing between the Caspian states on the status of the Caspian Sea - Azerbaijan, Kazakhstan and Turkmenistan insisted on dividing the Caspian along the median line, Iran insisted on dividing the Caspian by one-fifth between all Caspian states.
In relation to the Caspian Sea, the key is the physical-geographical circumstance that it is a closed inland body of water that does not have a natural connection with the World Ocean. Accordingly, the norms and concepts of international maritime law, in particular, the provisions of the UN Convention on the Law of the Sea of 1982, should not be automatically applied to the Caspian Sea. Based on this, in relation to the Caspian Sea it would be unlawful to apply such concepts as “territorial sea”, “exclusive economic zone", "continental shelf", etc.
The current legal regime of the Caspian Sea was established by the Soviet-Iranian treaties of 1921 and 1940. These treaties provide for freedom of navigation throughout the sea, freedom of fishing with the exception of ten-mile national fishing zones and a ban on vessels flying the flag of non-Caspian states sailing in its waters.
Negotiations on the legal status of the Caspian Sea are currently ongoing.
Delineation of sections of the Caspian seabed for subsoil use
The Russian Federation concluded an agreement with Kazakhstan on delimiting the bottom of the northern part of the Caspian Sea in order to exercise sovereign rights to subsoil use (dated July 6, 1998 and the Protocol thereto dated May 13, 2002), an agreement with Azerbaijan on delimiting adjacent areas of the bottom of the northern part of the Caspian Sea (dated September 23, 2002), as well as the trilateral Russian-Azerbaijani-Kazakh agreement on the junction point of the demarcation lines of adjacent sections of the bottom of the Caspian Sea (dated May 14, 2003), which established the geographical coordinates of the dividing lines limiting the sections of the bottom within which the parties exercise their sovereign rights in the field of exploration and production of mineral resources.
The Caspian Sea is a brief description of the endorheic salt lake of Eurasia and the largest lake on the planet is presented in this article. A message about the Caspian Sea will help you prepare for classes.
Caspian Sea: report
This water body is located at the geographical junction of Europe and Asia. The water level is 28 m below the level of the World Ocean. Over its long history, the Caspian Sea has “changed” more than 70 names. And it received its modern name from the ancient Caspian tribe, who were engaged in horse breeding and settled along the southwestern shore of the lake.
Salinity of the Caspian Sea not constant: near the mouth of the Volga River it is 0.05%, and in the southeast the figure increases to 13%. The area of the water body today is about 371,000 km2, the maximum depth of the Caspian Sea is 1025 m.
Features of the Caspian Sea
Scientists have conditionally divided the lake-sea into 3 natural zones:
- Northern
- Average
- Southern
Each of them has a different depth and composition of water. For example, the smallest part is Northern. The full-flowing Volga River flows here, so the salinity here is the lowest. And the southern part is the deepest, and, accordingly, salty.
The Caspian Sea was formed more than 10 million years ago. It can be called part of the ancient Tethys superocean, which once lay between the African, Indian and Eurasian continental plates. Its long history is also evidenced by the nature of the bottom and geological coastal deposits. The length of the coastline is 6500 - 6700 km, and including the islands up to 7000 km.
The shores of the Caspian Sea are predominantly smooth and low-lying. The northern part of the coastline is indented by islands and channels of the Ural and Volga deltas. The shore is swampy and low, covered with thickets. The eastern coast is characterized by limestone coasts that are adjacent to deserts and semi-deserts. The west and east coasts have winding coastlines.
Where does the Caspian Sea flow?
Since the Caspian Sea is an endorheic body of water, it is logical that it does not flow anywhere. But 130 rivers flow into it. The largest of them are Terek, Volga, Emba, Ural, Kura, Atrek, Samur.
Climate of the Caspian Sea
In the northern part of the sea the climate is continental, in the middle part it is temperate and in the southern part it is subtropical. In winter, the average temperature ranges from - 8 ... - 10 (northern part) to +8 ... + 10 (southern part). Summer average temperatures range from +24 (northern part) to +27 (southern part). The maximum temperature recorded on the east coast was 44 degrees.
Animal and plant life
The fauna is diverse and includes 1809 species. The sea is home to 415 invertebrates and 101 species of fish. It contains most of the world's reserves of pike perch, sturgeon, roach, and carp. The Caspian Sea is home to carp, mullet, bream, sprat, perch, kutum, pike, as well as such a large mammal as the Caspian seal.
The flora is represented by 728 species. The sea is dominated by diatoms, brown algae, red algae, blue-green algae, chara algae, ruppium and zoster.
The importance of the Caspian Sea
On its territory there are many gas and oil reserves, the fields of which are at the development stage. Scientists have calculated that oil resources amount to 10 billion tons, and gas condensate - 20 billion tons. The first oil well was drilled in 1820 on the Absheron shelf. Limestone, sand, salt, stone, and clay are also mined on its shelf.
In addition, the Caspian Sea is popular among tourists. Modern resort areas are being created on its banks; mineral waters and mud contribute to the development of health complexes and sanatoriums. The most famous resorts are Amburan, Nardaran, Zagulba, Bilgakh.
Environmental problems of the Caspian Sea
Sea waters are polluted as a result of the extraction and transportation of gas and oil on the shelf. Pollutants also come from the rivers that flow into it. Poaching of sturgeon caviar has led to a decrease in the number of these fish.
We hope that the report on the Caspian Sea helped you prepare for the lesson. You can supplement your essay about the Caspian Sea using the comment form below.
V. N. MIKHAILOVThe 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 feature of a reservoir is the instability of the level with sharp drops and rises. The last increase in the 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 have been flooded and submerged. Roads and power lines, engineering structures of industrial enterprises and public utilities are being destroyed. 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 of the Volga delta have 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 of 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 absolute 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. The natural conditions of the 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 sea level rise. 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 levels were higher than they are now, and this was in no way perceived as an environmental disaster. 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 other 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 suffered by the national economy is not the rise in level, but the thoughtless and short-sighted development of a strip of land within the mentioned risk zone, freed (as it turned out, temporarily!) from under sea level after 1929, that is, when the level decreased below the mark - 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 noted 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 reservoir level.
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 higher sea levels, 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 disaster for the economy of the coastal zone only because of the unreasonable development by man 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.