Wednesday, April 7, 2010

THE GREAT AMU DARYA

INTRODUCTION

The Amu Darya (lit. "Amu River") is formed at the junction of the Vakhsh and Panj Rivers in Tajikistan and flows 2,400km to the watershed of the Aral Sea.

The river historically has been regarded as the boundary between Iran and the Turan (the ancient Iranian name for Central Asia), literally meaning "the land of the Tur", essentially referring to those nomadising beyond the Oxus and Jaxartes rivers, both Turkic and Eastern Iranian peoples (Sogdians and Khwarezmians) who lived in the region.

In classical antiquity, the river was known as the Ōxus in Latin and Ὦξος Oxos in Greek — the name of the largest tributary of the river. In Middle Persian the river is known as Wehrōd (lit. "good river").

Medieval Arabic language sources call the river Jayhoun (جيحون) which is derived from Gihon the name of the second river mentioned in the second chapter of the Biblical Book of Genesis (one of four rivers said to be issuing out of the Garden of Eden).

The name Amu is said to have come from the city of Āmul, now known as Türkmenabat.

The beginning of irrigated agriculture in the region dates back to the 6th-7th centuries B.C. and coincides with flourishing the most ancient civilization where irrigation was a major decisive factor of historical and socio-economic development.

The river's drainage lies in the area between the former empires of Genghis Khan and Alexander the Great, although they occurred at much different times. One southern route of the Silk Road ran along part of the Amu Darya northwestward from Termez before going westwards to the Caspian Sea.

DESCRIPTION

The river's total length is 2,400 kilometres (1,500 mi) and its drainage basin totals 534,739 square kilometres (206,464 sq mi) in area, providing a mean discharge of around 97.4 cubic kilometres (23.4 cu mi) of water per year. The river is navigable for over 1,450 kilometres (900 mi). All of the water comes from the high mountains in the south where annual precipitation can be over 1,000 mm (39 in). Even before large-scale irrigation began, high summer evaporation meant that not all of this discharge reached the Aral Sea - though there is some evidence the large Pamir glaciers provided enough melt water for the Aral to overflow during the thirteenth and fourteenth centuries A.D.

The main source of the Amu Darya is the Pamir River, which emerges from Lake Zorkul in the Pamir Mountains, and flows west to Qila-e Panja, where it joins the Wakhan River to form the Panj River. Another source is an ice cave at the end of the Wakhjir valley, in the Wakhan Corridor, nestled in the Pamir Mountains, near the border with Pakistan. A glacier turns into the Wakhan River and joins the Pamir River about 50 kilometres downstream.

The Panj River forms the border of Afghanistan and Tajikistan. It then flows west to Ishkashim where it turns north and then east north-west, It subsequently forms the border of Afghanistan and Uzbekistan for about 200 kilometres, passing Termez and the Afghanistan-Uzbekistan Friendship Bridge. It then delineates the border of Afghanistan and Turkmenistan for another 100 kilometres before it flows into Turkmenistan at Atamyrat. As the Amudarya, it flows across Turkmenistan south to north, passing Türkmenabat, and forms the border of Turkmenistan and Uzbekistan from Halkabat.

Amu Darya (Near Urgench)

It is then split into many waterways that are used to form the river delta before joining the Aral Sea, passing Urgench, Daşoguz (formerly Daşhowuz) and Nukus.

THE CHANGING COURSE OF THE AMU DARYA

It is believed that the Amu Darya's course across the Kara-Kum Desert has gone through several major shifts over the past several thousand years.

Historical records state that in different periods, the Amu Darya river flowed into the Aral Sea (from the south), the Caspian Sea (from the east) or both, similar to the Syr Darya. These changes in course have also been influenced by climate change and changes in the state of the environment in the region. The Aral Sea over time has similarly had a number of periodical changes of its water area, expansions followed by withdrawals.
Evolution of periodic fluctuations of the Aral sea water territory during 10000 BC - 1990 AC

Reference:
  • UNESCO. The Aral Sea Basin. Division of Water Sciences,1999.


For much of the time, the most recent period being in the 1200s to the late 1500s, it is believed that  the Amu Darya emptied into both the Aral and the Caspian Seas, the latter via a large distributary called the Uzboy River. The Uzboy splits off from the main channel just south of the Amudarya Delta. The flow through the two branches being more or less equal, but in some flood years most of the Amu Darya's flow split to the west and flowed into the Caspian.

People began to settle along the lower Amu Darya and the Uzboy in the 5th century A.D., establishing a thriving chain of agricultural lands, towns, and cities. The river was impounded in about 985 A.D. at the bifurcation of the forks by the massive Gurganj Dam, which diverted water to the Aral.

The dam was destroyed by Genghis Khan's troops in 1221, and the Amu Darya shifted its flows more or less equally between the main stem and the Uzboy. But in the 1700s, the river again turned north, flowing into the Aral Sea, a path it has taken since. Less and less water flowed down the Uzboy until, in the 1720s, the river's surface flow completely dried up.

In the 1950s and 1960s, much of the waters of the Amu Darya and Syr Darya were diverted to irrigate extensive cotton fields in the Central Asian plain. Before this time, water from the rivers was already being used for agriculture, but not on this massive scale. The Qaraqum Canal, Karshi Canal, and Bukhara Canal were among the larger of the irrigation diversions built. A new Turkmen Canal was also proposed to divert water along the dry Uzboy River bed into central Turkmenistan, but was never built.

The use of a high percentage of the water in the Amu River for irrigation (some 97% on average)since the late 1950s has been the main contributing factor to the current shrinkage being experienced by the Aral.