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Posts tagged Caspian Depression

Deltas and Wetlands of the Caspian Sea – June 10th, 2009

43.0N 49.9E

June 10th, 2009 Category: Image of the day, Lakes, Rivers

Caspian Sea - June 3rd, 2009

Caspian Sea - June 3rd, 2009

Volga River Delta

Volga River Delta

Ural River Delta

Ural River Delta

Various types of wetland and delta areas can be found on the shores of the Caspian Sea. The northern section of this immense lake is encompassed by the Caspian Depression, a low-lying flatland region.

The depression, which covers approximately 200,000 kilometers² (77,220 miles²), lies at the southern end of the Ryn Desert, and is in both Kazakhstan and Russia.

The Volga River and the Ural River, which forms part of the traditional boundary between Europe and Asia, flow into the Caspian Sea through this region. The deltas of the Ural and Volga Rivers are extensive wetlands.

Both deltas can be observed in detail in their respective close-ups. The fan-shaped Volga River Delta has, unfortunately, experienced significant wetland loss due to industrial and agricultural modification to the delta plain. Much of the water in and around the delta appears bright green due to algal blooms, intensified by fertilizers carried in by the river.

Tengiz Field

Tengiz Field

Kura River and wetlands

Kura River and wetlands

In fact, studies have shown that water pollution, mostly coming from the Volga River, poses a serious threat to the biodiversity of the Caspian Depression. Water pollution is contributed mainly by industrial, agricultural, and household discharges.

The Ural River Delta in Kazakhstan has a different shape from that of the Volga: rather than a wide triangular or fan-shape, it is longer and thinner. This is called a “bird’s foot” or “digitate” delta. Such deltas are often seen on sediment-rich rivers flowing into lakes.

Much of the Caspian Depression is below the level of the sea; its lowest point is 28m (92 ft) below sea level. Its eastern region comprises large areas of marshlands. One such marshy area in western Kazakhstan is the location of the Tengiz Field (see close-up), a huge source of oil.

The final close-up focuses on the western shore of the Caspian Sea, in Azerbaijan. Here, the Kura River enters the sea, discharging sediments. Onland, the dark green area in the center near the coast is swampy Gyzylaghadj State Reserve. Also called the Gizil-Agach State Reserve, it is a Ramsar Wetland that is an important wintering and nesting area for migrant, swamp and wild birds.

The Three Zones of the Volga Delta, Russia – May 20th, 2009

46.7N 47.8E

May 20th, 2009 Category: Image of the day, Lakes, Rivers

Volga Delta, Russia - May 17th, 2009

Volga Delta, Russia - May 17th, 2009

The Volga Delta is located in Russia’s Astrakhan Oblast. It is the largest inland river delta in Europe, and occurs where Europe’s largest river system, the Volga River, drains into the Caspian Sea in the Caspian Depression. The far eastern part of the delta extends into Kazakhstan.

The delta lies in the arid climate zone, characterized by very little rainfall. The region receives less than one inch of rainfall in January and in July in normal years.

Strong winds often sweep across the delta and form linear dunes. Along the front of the delta, one will find muddy sand shoals, mudflats, and coquina banks. Green algae, nourished by fertilizers, is present in the waters around the delta.

The Volga Delta has grown significantly in the past century because of changes in the level of the Caspian Sea. In 1880, the delta had an area of 3,222 km². Today the Volga Delta covers an area of 27,224 km² and is approximately 160 km across.

The changing level of the Caspian Sea has resulted in three distinct zones in the delta. The higher areas of the first zone are known as “Behr’s mounds,” which are linear ridges of clayey sands ranging from 400 m to 10 km in length, and averaging about eight meters in height. Between the Behr’s mounds are depressions that fill with water and become either fresh or saline bays.

The second zone, in the delta proper, generally has very little relief (usually less than one meter), and is the site of active and abandoned water channels, small dunes and algal flats.

The third zone is composed of a broad platform extending up to 60 km offshore, and is the submarine part of the delta.

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