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W21
Atlas pp. 6&17

Caspian Sea, Russia, Kazakhstan, Turkmenistan, Iran, Azerbaijan Water level fluctuations, past shorelines

Significance: The Caspian Sea, the largest inland sea in the world, is a vast landlocked basin where rivers flow in, but water escapes only by evaporation. Since 1930, the water level has fluctuated greatly, dropping from 2 meters to 28 meters or 92 feet below sea level until 1992, the rising sharply in 1993 to 1994. The drastic drops in water level has been caused not only by evaporation due to a slightly drier climatic pattern, but by diversion of water from the Volga River, which supplies 80 percent of the inflow, for irrigation of agriculture in the middle and upper Volga Basin and industrial needs all along the basin. The sharp water level rises throughout 1994 have flooded many coastal areas, especially in the north, and threaten structures related to the large oil industry along the northeast corner of the sea. Shuttle photography of the coastal shorelines will assist Earth scientists to document the water level changes and map changing shorelines.

Physical Characteristics: Completely landlocked, the Caspian Sea stretches north to south for 1200 km (734 miles) and averages 320 kilometers (180 miles) across. Its surface area is 1.5 times the size of the combines U.S. Great Lakes. The sea, cupped in a huge depression, is encircled by a band of lowlands, some of which are also below sea level. To the southwest, it is hemmed in by the high snow covered peaks of the Caucasus, while the southern shores are fringed by the forested slopes of Iran's Elburz Mounntains. Beyond the broad band of lowlands to the north of the Caspian are the rolling Volga uplands. The Volga Delta dominates the northwest shore. Along the eastern shore, almost completely cut off from the main body of water by long, low sandspits is a gulf called the Kara-Bogaz-Gol', which is almost as big as Lake Ontario. Though it is lower than the rest of the sea and water rushes in through the narrow channel, the aridity of region causes very rapid evaporation. In 1980, a dike was built to allow continued flow of water into this gulf, due to the rapid decline of the surface waters of the Caspian. The Zaliv Kara-Bogaz-Gol' remains a good indicator of relative sea level.

Climatic changes during the recent glacial period have resulted in several fluctuations in the Caspian Sea's depth and surface area. Traces of former shorelines can be seen in many places, some up to 50 kilometers from the present shore. During the winter, the shallow northern portion freezes over. The deeper southern portion (978 meters at its deepest point) remains unfrozen.

Observation Techniques: Low-oblique to near-vertical views using both the 100-mm lens for synoptic views and the 250-mm lens to detail shoreline features are requested. Look for eddies in the southern sea basin and photograph in the sun glint if possible, using the 250-mm lens. Coverage of the Zaliv Kara-Bogaz-Gol' is especially requested.

Center point: 42° N, 50° E