Earthshots: Satellite Images of Environmental Change

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» Aral Sea, Kazakhstan and Uzbekistan

We see a lot of change with the 40+ years of Landsat imagery, along with the historical aerial imagery in the archives at EROS. The drying of the Aral Sea is likely the most dramatic change occurring over the past several decades in this imagery.

The Aral Sea once covered about 68,000 square kilometers, a little bigger than the U.S. state of West Virginia. It was the 4th largest lake in the world. It is now only about 10% of the size it was in 1960. Coastlines receded several kilometers from what were once coastal communities.

The Aral Sea is a terminal lake. Large permanent snow fields and glaciers in mountain ranges feed the two major rivers that flow into it, but it has no outlet. Syr Darya flows into the northern part of the Aral Sea. Amu Darya flows into the southern part. (Darya means river in the Turkic languages of central Asia.)

The precipitation rate over the Aral Sea is very low, less than 200 millimeters per year. However, 1,000–1,200 millimeters of water evaporates from the sea each year. Therefore, stability of the water level greatly depends on inflow from these two rivers, which has diminished over the past few decades leading to the shrinking of the lake.

The sea has in fact split into two separate bodies of water, referred to as the North Aral Sea and the South Aral Sea. The North Aral has stabilized but the South Aral has continued to shrink and become saltier. Up until the 1960s, Aral Sea salinity was around 10 grams per liter, less than one-third the salinity of the ocean. The salinity level now exceeds 100 grams per liter in the South Aral, which is about three times saltier than the ocean.

The effects of this dramatic change are far-reaching, geographically, environmentally, and economically. The subsequent sections describe how a body of water this size could nearly disappear so quickly.

Map of the featured area.

While the entire Aral Sea is shrinking dramatically, these images show that the northern portion of the sea, while clearly smaller than it was in 1964 and 1977, is not losing water at the same rate as the South Aral. The North and South Arals became separated sometime in the 1980s. The two had been joined by the Berg Strait. By the time of the 1987 image, this strait became more of a land bridge.

In the 1990s, a dam was built to prevent North Aral water from flowing into the South Aral. It was rebuilt in 2005 and named the Kok-Aral Dam. It caused the North Aral water level to be stabilized with a lower level of salinity. Consequently, commercial fishing began to rebound.

Throughout the 2000s, the North and South Arals continued to develop as separate water bodies, and the South Aral continues to experience more drastic changes than the North Aral.

Syr Darya Source

The Kok-Aral Dam was completed in 2005 to control the water level of the North Aral Sea. This dam has prevented further decline of the North Aral Sea, and by 2011 it helped restore the water salinity level to the that of the 1960s (8 grams per liter).

A dam can be seen as early as the 1998 image. It’s the straight angled lines on the southernmost part of the North Aral. This earthen dike was built in 1992 and later replaced by a concrete dam in 2005. At times, water from the North Aral is allowed to flow southward into the South Aral through the dam in the Berg Strait.

The city of Aralsk is shown in the 1964 ARGON image on the coast of the sea. By 1977, the sea had retreated from the city but was still just a few kilometers away. As depicted in the 2015 image, Aralsk sits nearly 20 km from the water’s edge.

Commercial fishing in the Aral Sea peaked in the late 1950s. With the drop in water levels and rise in salinity, the fish that once thrived in the sea could not survive. As a result, commercial fishing was no longer sustainable by the early 1980s.

With the recovery of the North Aral, commercial fishing has started up again. It’s still just a fraction of what it was in the 1950s, but Aralsk is again processing fish at a new plant, established after the completion of the Kok-Aral Dam in 2005. Aralsk is not the thriving city it once was, but the return of the North Aral gives residents some hope of recovery.

Although using the dam to retain most of the water from the Syr Darya in the North Aral Sea has had beneficial results in Kazakhstan, it means the water in the south is even more depleted.

The Amu Darya, which flows through Uzbekistan into the South Aral Sea, is used now more than ever to irrigate crops, reducing the flow to the South Aral. Although improvements in irrigation efficiency could greatly reduce the amount of water used for irrigation, making these improvements has not been a high priority.

While the North and South Arals were separating into their own water bodies, the larger South Aral also divided into two lakes: the deep western lake and a shallower eastern lake. An increasingly long channel connects the two water bodies. This channel flows either direction depending on the wind and the relative levels of the two basins.

In the past, commercial fishing was also a major industry in the South Aral Sea. In the 1980s, as the salinity level in the Aral Sea was rising, flounder-gloss—a fish species with the ability to reproduce at salinities from 17 to 60 grams per litter—was introduced successfully into the Aral from the Sea of Azov. In the 1990s, it became the only commercial fish species available for catch in the Aral Sea. However, by the end of the 1990s, the salinity reached over 60 grams per liter, which made the South Aral uninhabitable for its last surviving fish species. The salinity level in South Aral is now over 100 grams per liter, and it has no fish.

Recent images intermittently show water in the eastern lobe of the South Aral. While the 2014 image shows the eastern lobe of the South Aral as completely dry, the 2015 image shows the return of some water there. The presence of water in the eastern lobe depends on inflow from the Amu Darya and outflow from the North Aral. This cyclical drying and then refilling is expected to continue for some time, even with restoration efforts.

Amu Darya Source

The name Aral means Island. The sea did once have many islands. However, many of them stopped beings islands as the sea dried up. Two of the prominent islands were Vozrozhdeniya and Barsa-Kelmes. Throughout the series of images, they first become larger, then they become peninsulas. They are now fully connected with the mainland.

Vozrozhdeniya Island became infamous as the location of the Soviet Union’s secret biological weapons program. In the 1950s, Vozrozhdeniya was a small, isolated island in the middle of the sea. Until the collapse of the Soviet Union in 1991, various pathogens were tested, modified, and possibly weaponized on this island.

Vozrozhdeniya Island grew in size and joined the mainland around 2001. As the remote site became accessible, there was concern that the pathogens might have survived and spread to the mainland. In the early 2000s, experts from the United States helped Uzbekistan decontaminate the former island.

The former island Barsa-Kelmes is a nature reserve, established in 1939. Its natural isolation gave it great protection. But in 1999, the island became accessible, possibly threatening its pristine nature. It is now a desolate plateau, more vegetated than the surrounding dried sea bottom. However, this vegetation degraded as the sea disappeared.

For more information, see the book by Micklin and others, listed in the References section, pages 4 and 22.

The first question people have when seeing these images of the Aral Sea over time is, Where did the water go?

The images that go along with this section show where a lot of it is going. These images are from a Landsat scene south of the Aral Sea, upstream along the Amu Darya. The urban area in the center of the close-up image is Urgench, Uzbekistan.

Both images show extensive irrigated cropland, and the river seems to be at full bank. Canals can be seen stretching across the region, along with several pools of stored water. There is still plenty of water in the rivers that feed the Aral, it’s just being used before it can get there.


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