GEOGRAPHICAL, GEOLOGICAL AND METEOROLOGICAL CHARACTERISTICS OF THE CASPIAN REGION

The Caspian is the world's largest body of water that is not connected to the ocean, accounting for more than 40 per cent of the overall volume of the global lacustrine waters.

The Caspian has three main basins: the North Caspian (about 25% of the total area), the Middle Caspian (36%), and the South Caspian (39%). The natural boundary between the North and the Middle Caspian is the Manguishlaki Bank, which is a chain of structurally controlled shoals. The Middle and the South Caspian are separated by the Apsheron Bank, which is another tectonically controlled latitudinal elevation. The North Caspian is very shallow. Its average depth is 10 m, with the maximum being approximately 20 m, and it contains only around 0.5 per cent of the entire Caspian water. The Middle Caspian, with its 780 meters deep Derbent Basin, holds about 34 per cent of the entire volume of water. The South Caspian accounts for over 65 per cent of the Caspian water, and its maximum depth reaches 1,025 m.

The level of the Caspian is closely connected with its basin's regime. The Caspian basin is situated between 61⁰24^' and 34⁰49^' of northern latitude and 31⁰59^' and 60⁰59^' of eastern longitude including the basins of the large rivers: Volga, Ural, Kura, Terek and others (about 130 rivers on the whole). The drainage basin area is 3.5 million km². The ratio between the areas of the water surface and the drainage basin (1:10) testifies to the fact that the whole natural water surface background is considerably influenced by drainage basin processes. The Volga basin (its area equaling to 1.38 million km² which is 40% of the drainage basin of the Caspian) plays the most important role in feeding the Caspian .

The Caspian morphometric characteristics change with the change of level. The geographic coordinates of the extreme points of the current water expansion of the Caspian (Kara-Bogaz-Gol excluded) are 47⁰07^' of the northern latitude in the north 36⁰33^' of the northern latitude in the south, 46⁰43^' of the eastern longitude in the west, 54⁰03^' of the eastern longitude in the east.

The water level of the Caspian is -26 m, the length of the Caspian along the median is 1,440km. The largest length from the north to the south along the meridian of 50⁰00^' of the eastern longitude is 1,040 km. The largest width is 440 km (along the parallel of 45⁰30^' of the northern latitude), the least - is about 200 km (along the parallel 40⁰30^' of the northern latitude). Its total area is 405,100 km² (table 3.1) which constitutes 18% of the total area of the Earth's lakes. The total length of the coastal line with Kara-Bogaz-Gol bay and islands is 7550 km.

The Caspian is divided into the Northern, Middle and Southern parts according to its morphological and geographic particularities.

The line connecting the Cheten Island with the Tub-Karagan Cape is taken for the conventional border between the Northern and Middle Caspian, the conventional border between the Western and Eastern Caspian is the line connecting the Kuuli Cape and Jiloy Island.

The Manguishlaki threshold as an element of the bottom relief is taken for natural morphological border between the Northern and Middle Caspian. This threshold extends from the Tub-Karagan island (10 m deep) to the Cheten island. The Middle and Southern Caspian are separated by the Apsheronian threshold. This undercurrent asymmetric height extends from the Apsheronian Peninsula to the Cheleken Peninsula. The largest depths are 140-150 m.

The area of the Northern Caspian is 115,200 m², its water area is 100,000 km². The Northern Caspian covers more than 24.3% of the water surface. The Middle and Southern Caspian areas are nearly equal. The total area of the Middle Caspian is 138600 km², the Southern part area is 151300 km² or correspondingly 36.4% and 39.3% of the total Caspian area.

The total volume of the Caspian water is 79,045 km^2, which is 44% of the total reserves of lake waters on the Earth.

The Caspian level variations cause changes in the water volume, water surface area, coastal line and depth.

Water area and water volume of the Caspian at different levels.

The average water temperature tends to increase by 0.8°C per degree of latitude from north to south (from 0°C to 10.7°C in winter and from 22°C to 28°C in summer). The salinity of the Caspian ranges from 0.02 to 1.35 %, with an average salinity of 1.28 %. The North Caspian has the lowest salinity.

Rivers determine the Caspian water balance. Over 130 streams and rivers flow into it, but the Volga runoff accounts for around 78 % of the total annual inflow. The Ural and Terek also contribute to the North Caspian. Together with the Volga their combined annual flow accounts for about 88 % of all river water entering the Caspian. Flowing in on the western coast are the Sulak, Samur, Kura and several smaller rivers, which account for a total of 7 per cent of the inflow. Direct precipitation over the Caspian amounts to approximately 200 mm annually.

A fairly complex pattern of water currents, by and large following the cyclonic circulation of water, is observed within the confines of the Caspian water body. There is a wind-drift current of the Volga water running from the northern part of the Caspian past the western coast on southward. The Apsheron Peninsula breaks this current into two branches. Along the eastern coast, the water drifts from south to north. The flow rates attain 5-10 cm/s in gentle breezes and 30-40 cm/s in moderate gales. The other part of the Volga water flows along the northern coast to the east and joins the Ural water, thus forming local circulation.

The salinity of the central and southern Caspian’s water mass is stratified. This creates density turbulence. Intense vertical water exchange occurs in the upper water layer due to wind induced currents and dynamic turbulence.

Seasonal level fluctuations of the Caspian (deviations from average annual level) are no more than several tens of centimeters. Surge-related phenomena (higher, than 1,5 m) are especially conspicuous in the North Caspian. Those surges, caused by gales, are typical for the northwest coast. A particularly bad surge with disastrous consequences occurred on November 10-13, 1952 on the northwestern coast of the Caspian and in the Volga delta, when the water level near the town of Lagan rose by 3 to 4.5 m and a 25 to 50 km strip of land was flooded.

One of the most striking phenomena of the Caspian is the periodic variability of its level. Throughout recorded history the level has been lower than that of the world ocean. Since the beginning of scientific surveys of the Caspian level (around 1830) the variation in amplitude has been nearly 4 meters, from -25.3 m (relative to the zero reference level of the world ocean) in the 1880s to -29 m in 1977. This century has seen two major changes in the Caspian level. In 1929 the level stood at about -26 m. Since it had not changed for nearly 100 years, this level was considered to be a perennial, or secular, average. In 1930, however, the water level started to fall rapidly, dropping by nearly 2 meters by 1941. This regression continued until 1977 down to the mark of -29.02 m, the lowest level registered in the past 200 years.

Then the Caspian level began to rise again in 1978. In 1994, it stood at -26.5 m; i.e. in the sixteen years it rose by more than 2 m, at an annual rate of 15 cm. By 1991 the water level had risen to 39 cm. Currently the rise seems to have stagnated. However, the future development is not predictable.

Significant deposits of hydrocarbons have been found both on- and offshore. The Caspian’s paleogeography includes stages of exposed, semi-isolated and isolated basins. Its recent geological history is characterized by abruptly changing regimes. Alternating transgression and regression epochs determine the development of the coastal zone. The younger part of Caspian coast is characterized by loose Quaternary formations. Outcrops of bedrock, such as Sarmatian and Upper Khazar petrified limestone and conglomerates, are rare and are observable only on the coast of Daghestan. Oil and gas deposits are mainly linked with Jurassic and Cretaceous deposits. There are small stocks of deposits in Triassic and Paleozoic. Well-known fields are :the giant oil field Ozen, and the biggest fields Zhetibai, Kalamkas and Karazhanbas. The whole thickness of the deposit cover riches 4.4 - 5 km and even more in some places.

The Caspian Region of Azerbaijan

The Apsheron region, including the capital of the Republic of Azerbaijan Baku as well as Sumgait, is from the orographic point of view the continuation of the southeastern extremity of the main Caucasian ridge. The characteristic features of the south-eastern part of the Big Caucasian mountainous system within the Azerbaijanian territory are the lower heights in comparison with its central part. In Azerbaijan the heights of the Big Caucasus become lower to the southeast.

The Apsheronian folds form the peculiar south-eastern extremity of the Big Caucasian system. The biggest heights of the Apsheron Peninsula amount to 340 - 350 meters on the border with Gobustan. There are many mud volcanoes in the south-western part of the Peninsula (Lok-Batan, Akhtarma, etc.)

The eastern part of the Apsheron Peninsula extending to the east of the villages of Mashtagui and Surakhani is a low-lying flat but only somewhere slightly hilly plain, the maximum height of which does not exceed 38 meters. Some parts of this plain are even below the level of the Caspian .

From the northwest to the east the city of Sumgait is surrounded by the Sumgaitchay river falling into the Caspian . The length of the river is 182 km.

The tertiary rocks of the Apsheron Peninsula include mainly argillaceous rocks and limestone.

The climate in Baku and Sumgait is arid. Winters are soft and summers are hot and lasting. The average annual air temperature is +14 - +15°C, the average air temperature in January is +3 - +4°C, in July - +24 - +26°C. The annual temperature difference amplitude is not very big and makes in the average 21 - 22°C. The largest quantities of precipitation fall during fall and winter, the average annual precipitation is 200mm according to the precipitation gauge figures, the maximum quantities of precipitation - 300mm are observed in November.

The average annual relative air humidity is 73%, in the evening 75 - 80%, in the daytime 65 - 70%. In winter the relative humidity for many years has been 80 - 83% in the morning and in the evening, in the daytime it has been 70 - 73%. In summer these figures are by approximately 10 - 15% less than in winter.

The wind regime is the most characteristic feature of the climate with the predominance of the north and north-western directions. The winds blow several times a month regardless of the son. The local name of the north winds is "Khazri". Within cold air masses the wind velocity often reaches 20m/sec. The average annual wind velocity is about 6 - 7 m/sec.

Hydrogeological conditions of the region are very complex in character and diverse. There are four groups of natural factors and one group of artificial factors that influence origin and regime of underground water. These are geological and geomorphologic, climatic, hydrological, biogenic and anthropogenic factors.

Natural factors are relatively stable, their impact on the regime keeps constant in time (terrain, geological structure) or sometimes natural factors are subordinated to a certain cyclic recurrence (climate, hydrology, etc.) The artificial factors are dynamic. In this respect there are two kinds of underground water: natural and disturbed water. Geological and geomorphologic factors being very important in forming underground water and its regime create favorable conditions for its accumulation and distribution.

Hydrologic factors mainly determine the drainage conditions of the underground water. The rising level of the Caspian has recently led to a rise of the underground water level. The chemical composition of the water is usually characterized by chlorides, sulfates and bicarbonates. The underground water in deluvial-proluvial deposits is a rare occasion and is to be found in isolated areas mainly to the north-west of the Sumgaitchay river. The underground water usually occurs at a depth of 1.2 - 5.3 m, and on the Sumgait plain - at a depth of 1.3 - 6.1m. The water can be slightly salty, salty or very salty, the dry residue is 3 - 126 g/l, but more often - 20-30 g/l.

In new Caspian and modern littoral deposits the underground water is distributed along the coast of the in a zone of 60 - 1,500m wide. The water occurs there at a depth of 7 meters, and the depth tends to increase as the underground water zone moves away from the coast. The general mineral content is 0.3 - 13.6g/l. with chloride, sulfide, bicarbonate, sodium and calcium as main components.

In the Khvalyn layer deposits the underground water can be found along the coast. The underground water occurs at a depth of 16-17m in this case, the general mineral content is 0.3-17.6 g/l with bicarbonate, chloride, sulfate, calcium, sodium and magnesium as main components.

The Caspian Region of Iran

The Caspian is the north coast of Iran. Most of Iran’s forests and wetlands are in this region, which is considered to be the greenest part of the country. The provinces of Mazandaran and Gilan share the waters of the Caspian. The salinity of the water on the Iranian side is about 14,000 - 16,000 ppm,. creating a unique and delicate environment for the marine species living in the Caspian.

The rich ecosystem of the Iranian coastal area of the Caspian at the foothills of the Alborz mountains, is an ideal breeding place for many types of birds. Its flora and fauna are divers and abundant. Many migrating birds visit this area every year.

It has been feared that changes in the marine fauna would lessen the attraction of the Caspian as a flyway, which had already happened in the adjacent Aral . The green province of Mazandaran with a surface area of 46,956 sq. km has a border with Turkmenistan in the north. West of Mazandaran lies the province of Gilan, in the south the province of Semnan and Tehran and in the east Khorasan. Three major roads (Haraz, Chalous and Firouzkooh) and a railroad line connect this province with Tehran.

The climate of Mazandaran is generally temperate, but with intense variations, very cold winters in high altitude areas and very hot and humid summers on the lower areas and coast line. Almost 60% of this province consists of Alborz mountains including the Damavand peak (5672 m).

Gilan is one of the most historic provinces of Iran. With a total area of 14,820 sq. km. is borders in the north on the Caspian , in the west on the province of Ardabil, in the south on Zanjan and Ghazvin and in the east on Mazandaran province. A major road from Tehran to Rasht connects the province to the capital.

The Anzali wetlands, a very well known wildlife and bird sanctuary hosts a great variety of migrating birds.

The climate of Gilan is very temperate. Cold winters in the southern high lands of the province and hot, humid summers on the coast line are typical for this climate, Gilan has the highest precipitation in the country (about 1200 mm per year). Gilan is mostly covered by forests and woodlands.

Growing rice and citrus crops are the main land products of its farmers. Over 80 percent of Iran’s tea is grown in Gilan. Fishing and fish processing is also a main source of income.

The Caspian Region of Kazakhstan

Kazakhstan has about 2,300 kilometers of shoreline on the northern and northwestern Caspian between Russia in the west and Turkmenistan in the south.

Kazakhstan is rich in mineral resources and petroleum. The Republic produces 50 elements of Mendeleev's periodic table in the form of metals, alloys and chemicals. It has 90% of world stock of tungsten, and significant resources of chromium, copper, iron, lead, gold, uranium, oil, gas, phosphorus and many other important minerals.

The northern part of the Caspian is shallow. Its salt content varies. From the Volga and the Ural rivers fresh water flows into the Caspian. Geologically, it is characterized by sediments of the Cenozoic, Mesozoic and Paleozoic periods that lie on crystalline blocks of the archaic base. In some ancient parts it is considered to have Proterozoic sediments. According to geological structure and the degree of metamorphism of depth (deposits) the sediment cover is divided into 3 structural levels: super-saline, saline and sub-saline.

The super-saline level is built of friable and weakly metamorphosed sediments of Cenozoic, Mesozoic and upper Permian formations. It contains oil layers of high quality. The saline level of the lower part of the Permian system contains Kungurs rock and layers of saline rocks of terrigenous stratum, anhydrides, dolomite and limestone. It is characterized by salty tectonic and plastic current of rock salt in its depth.

The thickness of the salt changes from zero (in molds between domes) up to several kilometers (in kernels of the salty domes). The sub-saline level mainly consists of terrigenous and carbonic deposits with minor quantities of imbedded anhydride. There are gigantic deposits of oil, gas and condensate fields such as: Tengis, Carachaganak, Zhanazhol, etc. Lower horizons of the level have not been well studied yet. The sub-saline level is also characterized by difficult conditions for drilling and oil extraction. Much depends on the depth (more than 5 km) and the presence of extremely high temperature (more than 100 C) and high concentration of hydrogen sulfide (18-22%).

The climate on Kazakhstan’s shore of the Caspian coast is continental as all over Kazakhstan. The average summer temperature is about 30-35°C, sometimes +40°C. Winter temperatures can drop below -20°C. The amplitude temperature over the Caspian reservoir is 3 - 4°C less than on land. Snow and ice covers are formed only in the northern part of the Caspian . The ice cover in the northeastern part can be 40-50 cm thick and in the west up to 20 cm. Winter lasts about five months in the northern part of the Caspian and about 2 months in its central part.

The Kazakhstanian region of the Caspian usually is dominated by breezes, sometimes interrupted by fully calm periods. In winter many days are stormy, especially in January. The wind speed reaches 10-15 m per second, sometimes 30 m/second. In fall and spring stormy winds in the northern and northeastern Caspian cause high waves up to 1.3 - 4.5 m and flood large areas of land as far as 20 km and sometimes even 50 km from the coast.

The Caspian Region of Russia

The Russian part of the coast is 695 km long and constitutes the northwestern segment of the Caspian shoreline. Geologically, the coast is heterogeneous and is characterized by diverse structural conditions and a unique paleogeographical development. The entire northern coast and the adjacent shallow water areas of the North Caspian are situated in the Caspian syncline of the Russian Platform, an area of stable saline dome tectonics and a thick series of fresh Pliocene Quaternary formations. South of the deep fault that forms the boundary of the depression, there are uplifts of the Epihercynian Scythian-Turanian Platform whose sedimentary mantle is represented by Mesozoic and Cenozoic sediments and is separated from the Cenozoic basement by an intermediate Permian-Triassic complex.

The relief of the Caspian coast in the Russian Federation is clearly divided into three large regions: the Volga delta in the Astrakhan Oblast; the Terek-Kuma plain in Kalmykia and Daghestan and the narrow coastal plain bordering the territory of the middle and southern parts of Daghestan.

The coast of Daghestan and the western part of the Middle Caspian are situated in the North Caucasian forefront of the folded region filled with an 8-10 km thick series of Meso-Cenozoic formations dislocated and broken into folds. A wide seismic belt stretches along the coast of the Caspian . Foci of potentially strong earthquakes lie this zone at various depths. An especially violent tremor was the 1970 Daghestan earthquake of magnitude 9 according to the MSK-64 scale in the epicenter. It has caused much more frequent landslide processes.

The climate of the Russian coast is moderately continental, changing to sub-tropical in the south and to arid, with hot summers and relatively mild winters. In the northern part of the Caspian the coldest month is January and the warmest June. The temperature in January varies from -7°C to 2°C and the average in June is +25°C. Duration of the frost period decreases from north to south and from east to west. The largest annual amplitude of air temperature is observable over the northwest part of the Caspian (25-27°C). The longest period with daily average air temperature below freezing is 113 days for Astrakhan and 100 days for the Iskusstvenny Island. The North Caspian freezes in the winter. In harsh winters, almost the entire water area of the North Caspian is covered with ice, sometimes from November to March. The shore ice is 35-40 cm thick in moderate winters and 70-90 cm in cold winters. Shore ice is not formed in southern areas, but broken ice may form dense accumulations in harsh winters. Large amounts of ice hummocks are observed in the Astrakhan area and near the Chechen and Tyulenii islands where ice piles may become 3-6 m high. 18 - 43 days per year the Caspian coast is covered with snow. In Daghestan no snow cover is formed in 50% of winters.

The most storm-affected area is near Makhachkala because of the mountainous topography combined with the complex shape of the shoreline. Interaction of local pressure systems (over the warm land and cold ) creates a monsoon pattern of wind flow on the coast: Winds from southeast and east prevail in summer and from west and northwest in the cold period. The monsoon pattern of the circulation is less observable in winter than in summer. The average annual wind velocity is 5 - 6 m/s and the highest average monthly velocity 7.6 - 8.7 m/s. Stormy winds with velocities in excess of 15 m/s occur in the entire coastal area.

The Russian part of the Caspian coast has three vegetation zones: desert; semi-desert; and arid steppe. Considerable areas in the region are covered by sand and sandy soil. Their agricultural use is insignificant.

A small portion of the territory of the foothills of Daghestan is occupied by chestnut and light chestnut soils. Chestnut soils are most frequently used for vineyards or orchards and light chestnut soils for pastures. A considerable area on the coast is occupied by reed thickets that stretch in several kilometers wide belts in the Volga delta and in the coastal zone in Kalmykia.

The coastal fauna is typical of steppe and semi-desert areas: numerous rodents, steppe birds, reptiles (lizards, snakes, tortoises), saiga, corsac fox. Jungle cat and numerous waterfowl occur in reed thickets. Jackals and wild boars live in the plain of Daghestan. A highly diverse avifauna is found in the Volga delta. The North Caspian is rich in fishes (sturgeon, giant sturgeon, salmon, various small fishes).

The most vulnerable areas on the Russian coast are the wetlands in the lower Volga delta and some other areas that fall under the jurisdiction of the Ramsar Convention of 1971 as habitats of waterfowl. Parts of the Astrakhan State Biosphere Reserve and the State Reserve Dagestanskyi are located on the Russian coast. They were established to protect flora and fauna threatened by anthropogenic impact and rise of the water level. Since 1975 a part of the Caspian water body north to the mouth of the river Sulak has been declared a protected area.

The Caspian Region of Turkmenistan

The coastline of the Caspian in Turkmenistan extends 470 kilometers from north to south. However, if the shores of the numerous gulfs in western Turkmenistan are counted, it exceeds 1,000 kilometers.

In winter the weather over the central Caspian is unstable weather and often the wind often changes its direction. The wind strength goes sometimes up to 9-10, and the air temperature fluctuates significantly. The weather is influenced by continental polar air, Siberian anticyclones and arctic air from the Kara and Barentz s. Winds from the east bring rather dry air with moderate frosts. Strong winds from the north cause sharp cooling and snowstorms. The southern part of the Caspian has usually cloudy but dry weather in the winter.

The monthly average temperature of January - February varies from 2-3°C in northeast up to 3-4 degrees in the south. Frosts are observed in January and February. The historically observed minimum was - 27°C. In the southernmost part winter temperatures can reach 8 - 12°C and frosts are rare.

The probability of ice forming in winter consistently decreases from 100 % in the north to below 40 % in the south. The probability of complete freezing, i.e. formation of a motionless ice cover to the visible horizon, is 27 % in the gulf of Krasnodar. However, in the central Caspian such a cover does not stay throughout the winter, but may appear five to seven times for a short period of time during the son.

In the south, ice covers appear only in extremely adverse winters in the Chelekenskiy and Turkmenskiy Gulfs. The width of floating coast ice can be in Beckdash up to 0,5 km, in Karabogazgol up to 1,4 km, in Cheleken - up to 7 km and in Turkmenbashi 7 - 10 km. The thickness of motionless ice in the same places reaches 15 - 30 cm.

In March the central Caspian weather is warmer but unstable with frequent storms and fog, but in April the Caspian warm air flows from the Azores to the Caspian and. Causes clear, dry and warm weather. The air temperature quickly rises to 16-18 degrees and in the extreme south up to 20 degrees. In summer it is hot and dry with mainly weak winds. The monthly average air temperature in July and August is 24-28°C with highs of 40-45°C. In fall the weather becomes again unstable. The wind frequently changes direction and speed. The air temperature in October is about 20-22°C.

Local wind speeds differ considerably in different parts of the Caspian. Over the central Caspian and on a significant part of the east coast dominate east winds in the cold and north-west and west winds in the warm son. The Karabogazgol region gets strong winds in with speeds up to 30 m/s have from east and south-east. This condition often lasts several days. Because of non-uniform heating and cooling of the Caspian and shore, local winds are common. These “monsoons” appear particularly in the south. During the warm son the Caspian is cooler than the land and the monsoon blows towards the Caspian. Vice versa, when the water it is warmer than the land in winter, the monsoon blows from the Caspian.

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