The arrow-shaped island in the Aral Sea used to be a 35-kilometer-long visual marker, indicating the Aral Sea to astronauts. An image from the present International Space Station increment shows how much the coastline has changed as the sea level has dropped during the last three decades.
The Volga River drains much of western Russia’s industrial region as it travels southward to empty into the Caspian Sea. Over thousands of years, the river has built a tremendous delta that forms the northwestern shoreline of the Caspian Sea. The delta channels provide transportation between the heartland of Russia and the oil-rich Caspian Sea. The Volga’s extensive distributaries (branches to the sea) harbor habitat and rich fishing grounds for Russia’s famous beluga sturgeon, the source of beluga caviar. The delta’s wetlands, parts of which are designated as the Astrakhanskiy Biosphere Reserve, are important stopping points and breeding grounds for migrating water birds. This detailed astronaut photograph zooms in on a shipping channel in the western part of the delta.
The Aral Sea has shrunk to less than half its size since 1985. It receives little water (sometimes none) from the two major rivers that empty into it—the Syr Darya and Amu Darya. Instead, the river water is diverted to support irrigation for the region’s extensive cotton fields. Recently, water scarcity has increased due to a prolonged drought in Central Asia. As the Aral Sea recedes, its former seabed is exposed. The Aral’s sea bed is composed of fine sediments—including fertilizers and other agricultural chemicals—that are easily picked up by the region’s strong winds, creating thick dust storms. The International Space Station crew observed and recorded a large dust storm blowing eastward from the Aral Sea in late June 2001. This image illustrates the strong coupling between human activities (water diversions and irrigation), and rapidly changing land, sea and atmospheric processes—the winds blow across the Sea and pick up dust (former sea bottom sediments) as soon as the blowing air masses hit land.
The Ural River is one of the two major rivers (the other is the Volga) that empty into the northern coast of the Caspian Sea, creating extensive wetlands. This image shows details of the Ural’s tree-like (or “digitate”) delta. This type of delta forms naturally when wave action is low, and sediment content in the river is high. New distributary channels form in the delta when the river breaches natural levees created by sediment deposition. The long main channel of the river in this image and several of the distibutary channels are too regular to be entirely natural, however. Like the famous Mississippi River delta in the United States, the Ural River delta has been significantly modified to reduce flooding and divert water.
This elevation image shows that the Irrawaddy Delta in Burma (Myanmar) is clearly flat, much of it below five meters in elevation. This low elevation makes the delta particularly prone to flooding from storm surges.