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Section: Biology
The Aral: Sea and Land

The Aral: Sea and Land

Only half a century ago the Aral Sea was the world's forth largest landlocked water basin. Its warm saline waters were full of life. However, very shortly afterwards, in the 1960s, the Aral began to shrink very quickly after the rivers Amu-Darya and Syr-Darya that fed it were diverted by irrigation projects. By the beginning of this century, the lake's surface area shrank to one-forth and its volume to one-tenth.
This process has not stopped yet: the Aral Sea continues to die slowly in front of our eyes. Studies of its history though demonstrate explicitly that in the past it was not always full of water either

It is not by chance that the lake of Aral was called a sea: not so long ago it was one of the world’s largest endorheic saline bodies of water. Situated among the Central Asian deserts, the Aral Sea was a blessing for this huge arid region. The prosperous fishing industry, well-developed cattle breeding, and occasional irrigated farming fed the residents of Kazakh and Kara-Kalpak settlements and the town of Aralsk.

Test boring was carried out on the exposed bottom of the Aral Sea in the fall 2008, within the new international project whose aim is to determine the sequence and evaluate the scale of the Aral transgressions and regressions

Today, the Aral Sea and surrounding area are a world-known example of an environmental catastrophe caused by humans. The sharp increase in water salinity (from 10 g/L to 160 g/L by 2004) produced a true collapse of the ecosystem. The sea bottom exposed with the shrinking of the Aral has produced dust storms carrying, along with dust and sand, salt and hazardous substances like pesticides that once made their way to the lake. The environmental catastrophe has touched upon, directly or indirectly, all of the Central Asian nations: it has affected vast areas of Kazakhstan and Uzbekistan, and repercussions of dust storms have reached the south of West Siberia.

In the last two decades, monitoring of the Aral crisis initiated by Soviet scientists has been carried on by international research teams.

The “Blue Sea” story

The lake of Aral has been mentioned as Kurder, Khorezm, or Dzhend Lake in the Arab manuscripts beginning with the 10th century, and vague indications to it were found with ancient historians. The Russians found out about the Aral Sea a long time ago. In Kniga glagolemaya Bolshoi Chertezh (Book of the Great Map, 1627), which was description to the first map of the “entire Moscow state”, the Aral was referred to as the Blue Sea for its particular dark blue water.

The name “Aral Sea” first appeared in 1697 on the map of the talented Russian cartographer S. U. Remezov called “The Draft of the Land of the Waterless and Difficult Stone Desert”. The word “Aral” means an “island” in Turkic languages. According to the historical treatises of the Khiva Khan Abulgazi, who lived in the first half of the 17th century, it was first used to denote the place where the Amu-Darya fell into the lake.

The Aral studies were initiated in the late 18th century by Russian officers who were members of the expeditions organized as part of the state policy to colonize Central Asia. The expedition headed by Commodore A. I. Butakov (or Butakoff) drew the first map of the Aral Sea based on geodesic tool measurements. It is this map that has given us the idea that the Sea of Aral was a vast body of water.

The Aral Sea level standard for the 20th century was 53 meters above the Baltic Sea level. A few centuries earlier, however, camels used to roam around the Aral bottom

The Aral looks almost the same on the very accurate pilot chart published by the Department of Hydrographic Service of the USSR Navy in 1962. The long-term average level of the Aral Sea shown in the chart—53 meters above the world ocean level—has become a benchmark for the 20th century. But has the Aral Sea always had so much water?

The Aral’s changeable nature was no secret ages ago. Medieval Arab manuscripts mentioned several times that the lake had shrunk and the rivers that fed it—the Amu-Darya and Syr-Darya—had changed their flow. However, proper studies of the Aral Sea began in the 20th c. with the works of well-known Russian orientalist V. V. Bartold and Academician encyclopedist L. S. Berg. Detailed investigation into the Aral’s latest Pleistocene and Holocene history was conducted by the specialists of the Khorezm archaeological-ethnographic expedition, from 1937 to the Soviet Union collapse.

The chart showing changes in Aral’s water level in the last 6,000 years drawn by the end of the 1990s was predominantly based on geological-geomorphic and archaeological data.

The chart lacked radiocarbon age estimations: for the entire huge Sea of Aral, there were less than ten dates.

A new round of studies using up-to-date technologies was initiated by a project of INTAS, the International Association for the promotion of CIS research activities through developing cooperation with Western European countries. The most important achievement of the project “Aral # 00—1030” carried out from 2002 to 2005 was the recording of the Aral natural changes and water level variations occurred in the last 2,000 years, which was obtained from the examination of bottom deposits samples.

So what can we say today about this small but the most clear part of the Aral Sea history?

Mausoleums on the sea bottom

On the exposed bottom of the Aral Sea, not far from the former island of Barsakelmes on the northern coast, expeditions of Kyzylorda State University (Kazakhstan) have found ruins of medieval settlements. The groups of monuments called Kerderi-1 and Kerderi-2 are dated 14th century. They are 60 km away from the 1960 coastline, and during the maximum of the last transgression were at a depth of 20 meters.

How could a man survive amid this flat salty plain? Judging by the abundance of domestic animals’ bones, pottery fragments, pieces of bronze artifacts and grindstones strewn over the area of several hectares, and the necropolises found nearby, these were permanent settlements. Most likely, they would spring up along the caravan routes going across the dry sea bed. The question is, however, where did the residents of these settlements take water from? The Aral water, same as the ground water, was certainly too salty.

On the basis of the manuscripts, it was believed that the medieval Syr-Daria lost in the sands did not reach the sea. However, analyzing some recent space photographs of the Aral’s exposed bottom, we discovered the ancient bed of the Syr-Daria River. It has appeared to have come to the Aral shore about 30 km further to the south than it does now and flow about a hundred kilometers along its bottom. People were thus able to inhabit this lifeless expanse thanks to the presence of fresh water.

What was the reason for the medieval regression? The water level could have been affected both by the natural and anthropogenic factors. Firstly, it was the 14th century that witnessed the change of the climatic epochs: the medieval climatic optimum ended and the Little Ice Age began. Possibly, reduction in the river runoff caused by precipitation conservation in the Pamir and Tien Shan glaciers dates back to this time.

Secondly, along with the climatic changes, people contributed to the Aral shrinking. In 1221—1222 Chinggis Khan’s conquest led to neglecting the irrigation systems in the southern Aral region; in particular, the earth dike near the ancient city of Urgench that directed the Amu-Darya waters to the lake. As a result, the water went largely to the Sarykamysh Hollow. Probably, the dike had not been reconstructed since then, and Urgench was completely wiped off the face of the earth by Tamerlan in 1388.

These Amu-Darya flow conditions were observed by the British merchant and explorer Anthony Jenkinson in the mid-16th century. The Khiva Khan Abulgazi stated that the Amu-Darya turned back towards the Aral 30 years before his birth, that is, approximately in 1573. By the end of the 16th century, the Aral Sea was again full of water. The above-mentioned Book of the Great Map maintained that the voyage across the Blue Sea (from the west to the east) was 250 versta’s long (in the 17th c., a versta was about 2.278 km).

The medieval bed of the Syr-Daria River—one of the two rivers that feed the Aral—was detected as a result of examination of recent space photographs showing the Aral Sea exposed bottom. You can easily see the delta protruding into the opposite western slope of the sea bottom.
Only a few years ago the delta was half flooded but by 2008 it jutted out completely above the water. The Aral Sea level reconstructed from the ancient delta is 30 m above the sea level—it is commensurable with the scale of the modern regression, which exceeded the medieval regression only in 2008

We can thus reason that the phase of the lower level of the Aral Sea and its subsequent rise lasted about 300 years (from late 13th c. to late 16th c.). The Aral was at its lowest for quite a long time, over a hundred years (according to the archaeological data, this occurred in the 14th century).

Evidence of variations in the sea level was found on its southern shore too. About 70 km to the south from the 1960 coastline, under the Usturt Plateau’s face there is the closed Karaumbet basin (now a salt deposit). For a long time, it was the confluence of the Amu-Darya distributary Laudan that fed the once flourishing oasis. Archaeological data indicate that people lived there from the 1st to the 5th century and from the 12th to the 14th century. On the river bank there was a town with rich manors, the last “outpost” before the waterless Usturt for the caravans taking this branch of the Silk Road.

Interestingly, the area of the town and ruins of its houses are strewed with shells of Cerastoderma, a typical Aral bivalve, which means that the town was flooded with the sea. In fact, the Butakov’s map shows the Aybughir, or Laudan, Bay that protruded into the Karaumbet basin. The upper layer of the basin’s bottom sediment corresponding to the Aybughir Bay has the radiocarbon age of 300 years.

On the basis of today’s refined data, we suggest that the Aral’s water level was the highest in about 1740.

Aral tested by numbers

In this way, thanks to research done in the recent years, we have reliable records of the Aral level variations in the last 2,000 years and less justified data for 6,000 years. Nevertheless, our knowledge of the Aral’s distant past is vague. Moreover, the data we have do not always allow a quantitative, and not just qualitative, evaluation of the water level dynamics.

This is why in 2008 the international project “Environmental history of the Aral Sea in the last 10,000 years: natural and anthropogenic components” was started. The project was supported by the Russian Foundation for Basic Research and U.S. Civilian Research & Development Foundation (CRDF). Participating in the projects are researchers from the Institute of Geology and Mineralogy SB RAS, Institute of Petroleum Geology and Geophysics SB RAS (Russia), University of Arizona (U.S.A.) and Kyzylorda State University (Kazakhstan).

The International Fund for Saving the Aral Sea - an intergovernmental organization that develops and sponsors environmental and practical research projects and programmes targeted at improving the situation in the Aral region—was founded in 1993. In August 2003 the Programme in the Aral Sea Basin (PASB-2) comprising about fifty regional projects was adopted.
Plans for the post-catastrophe relief actions in the northern (Kazakhstan) and southern (Uzbekistan) parts of the Aral Sea basin are very different. The main reason for this is that in each case the solutions best suited to the specific situation are chosen.
Kazakhstan is reviving the Small Aral Sea, the northern part of the lake is separated from its main part. A waterworks facility has been constructed to dam the Berg Strait connecting the Small (or North) Aral Sea and the Big (or South) Aral Sea, as a result of which the Syr-Darya waters fill the Small Aral Sea. To control the water flow, a water reservoir is being built in the Syr-Darya lower reaches. It is believed that the measures adopted will gradually turn the Small Aral Sea into a freshwater lake.
Uzbekistan is concerned about irrigation of the farmland in the Amu-Darya delta. To this end, a system of small reservoirs is being set up, which is going to feed the irrigation canals and ditches of this fertile area

The aim of the new project is to determine the sequence of the Aral’s transgressions and regressions and assess their size based on the data obtained by drilling: geological sections from the shore to the center of the lake.

The matter is that transgressive and regressive sediments can be easily distinguished. Regressions are normally marked by the layers rich in shells, and indicators of deep regressions are salt-bearing sections—evaporites and deltaic sand. Having examined layer distribution on sediment cores, one can judge with confidence how large or small the Aral Sea was in a certain epoch. Restoration of the ancient coastline will make it possible to estimate the volume of water, based on which paleoclimate can be readily reconstructed.

An important part of the project is radiocarbon dating preformed at the Accelerator Mass Spectrometry (AMS) machine at the University of Arizona. This facility allows calculating the age of deposits based on small samples that contain carbon: single mollusk shell, a hundred of seed shrimp (small crustaceans) valves, or a hundred of foraminifer (gigantic unicellular organisms) shells. The contribution of the American partners is essential—the cost of one such analysis performed by commercial laboratories is US $550—600, and the minimum of 100 age measurements is planned. It should be noted that neither Russia nor any other country of the former USSR has a similar facility yet, and the first such machine is being developed at the Novosibirsk Research Center.

As it is known, the Aral Sea level depends on the two rivers that feed it—the Amu-Darya and Syr-Darya. These rivers have changed their course more than once, carrying their waters sometimes to the Aral Sea, sometimes to the Caspian Sea (the Amu-Darya), and sometimes just to the desert. These changes were related both to natural wandering about the river deltas and to human activities. The new project is expected to reconstruct the chronology of the river-bed shifts of the ancient Amu-Darya and Syr-Darya in order to determine the relation between variations in the Aral Sea level and river runoff, and to make an attempt at distinguishing between the natural and the anthropogenic factors. After all, before we start making plans for the future, the more so the future of a sea, past lessons should be learnt.

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The photos are courtesy of the author

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