Historical changes of Aral Sea

The Aral Sea is located at the junction of Kazakhstan and Uzbekistan, in the middle of the Kizilkum Desert.

Fifty years ago, the Aral Sea covered a total area of 66,000 square kilometers, almost equivalent to the land area of Sri Lanka. Abundant water resources have brought great opportunities for the development of local agriculture and fisheries. According to statistics, the annual catch of local fisheries has reached 40,000 tons, there are dozens of small lakes in the tributaries of the delta, and the area of ecologically rich swamps and wetlands has reached 550,000 hectares.

Because the inflow of water (runoff) is less than the evaporation of lake water, the salt content of Aral Sea is much higher than that of freshwater lake. At its peak, the Aral Sea was once the largest saltwater lake in Central Asia and the fourth largest lake in the world, covering an area of nearly 70,000 square kilometers. At its peak, the Aral Sea used to have a well-developed fishery, with more than 40,000 employees along the coast, and the catch accounted for 1/6 of the total catch of the former Soviet Union. The English name of Aral Sea can be roughly translated as "Sea of Islands" because it once had 1500 islands within a hectare.

There are 1000 islands scattered in the sea. The north shore is rugged, with winding coastline and numerous bays. The northern part of the east coast is the huge Syr Darya Delta, the southern coast is the same as the Amu Darya Delta, and the western coast is the Ustut Plateau. There are marine deposits and continental deposits on the coastline, and the lake bottom is flat and inclined from east to west. Shi Ying, limestone, sand, clay and clay-limestone silt are deposited at the bottom of the lake, which are produced by river rapids scouring the coast and wind and ice erosion. The Aral Sea was once the fourth largest inland lake in the world, located in the Kizilkum Desert. Since the 1960s, the water diversion and irrigation projects in the Soviet Union have greatly reduced the area of the Aral Sea. Today, due to various reasons, the Aral Sea is still shrinking.

As the lake dried up, fisheries and other industries that depended on it collapsed. The constantly salinized water quality is gradually polluted by chemical fertilizers and pesticides. Dust blown on the bare lake bed, coupled with pesticide pollution, has become a local public health disaster. According to the relevant research of NASA, the effects of Aral Sea drying up also include: more extreme climate in this area, such as colder in winter and hotter and drier in summer. High-salt dust is blown from the bare lake bed to the nearby farmland, which leads to soil degradation, and crops must absorb more river water to maintain their growth needs.

1960, this salt lake covers an area of 68,000 square kilometers, which is a big lake. From 65438 to 0987, the Aral Sea was divided into two parts: the North Aral Sea and the South Aral Sea; 1998 has been reduced to 29,000 square kilometers, divided into two small lakes, making it the eighth largest lake in the world, and the salt content has increased from 10g/L to 45g/l; In 2004, there was only 1.7 million square kilometers left, which became three small lakes. By 2007, the combined area of the three small Aral Sea is only 65,438+00% of the peak of the Aral Sea. From the satellite images of NASA in August 19 and 20 14, it can be seen that the Aral Sea has shrunk to sporadic parts in the west and north. Official website, the Aral Sea Foundation, shows that the Aral Sea area has shrunk by 74%, while the water volume has decreased by nearly 85%.

Since the 1960s, the former Soviet Union diverted water from the Aral Sea to develop agriculture, especially cotton planting, and began to dry up gradually. FAO calls it a "model course of unsustainable development": the development of irrigation was once remarkable, from about 4.5 million hectares in 1960 to nearly 7 million hectares in 1980, and the local population increased rapidly, from 1980 in the same period. At the same time, as water resources experts said, the water balance table of Aral Sea basin was destroyed, many small tributaries were overexploited, and the unlined ditches and drainage pipe network caused low irrigation efficiency, which led to a large number of floods and salinization, which finally affected about 40% of irrigated land. Excessive use of pesticides and fertilizers has polluted surface water and groundwater, and the delta ecosystem has actually been destroyed: by 1990, more than 95% of swamps and wetlands have become deserts, and more than 50% of delta lakes have dried up.

19 18, the newly established Soviet government envisaged that the Amu Darya River in the south of the Aral Sea and the Syr Darya River in the north would be diverted to irrigate rice, melons, millet and cotton. This is part of the "Cotton Plan" or "Platinum Plan" of the former Soviet Union. At that time, planners hoped that cotton would become an important export product of emerging Soviet countries.

In the 1940s, large-scale canal projects began to be built. However, the quality of many channels is very poor, and a lot of water evaporates or leaks, which is wasted. It is estimated that 30%-75% of the water flowing in the Qaraqum canal, the largest canal in Central Asia, has been wasted, and the water leakage around the two major water sources in the Aral Sea will be quite serious. In the 1960 s, about 20-60 cubic kilometers of water were diverted from the Amu Darya and Syr Darya rivers to the desert near the Aral Sea every year.

From 19 1 1 to 1960, the average annual inflow of the Aral Sea is 56 billion cubic meters, the average water level is maintained at an absolute elevation of 53.3 meters, the water surface area is 66,000 square kilometers, and the total water volume is 1 trillion cubic meters. The former Soviet Union has a vast territory, but most of it is in cold high latitudes. In order to develop new reclamation areas, cotton, rice and vegetables are planted. As early as in Russia, I dreamed of reclaiming wasteland in Central Asia, expanding irrigated land to grow cotton and solving the problem of cotton dependence on imports. Using the Syr Darya River, 1937, the former Soviet Union built a 220km-long figuera Grand Canal to irrigate cotton fields. 1906 put forward the idea of using the Amu Darya River to develop the southeast of Karakum Desert, but due to the constraints at that time, the idea could not be implemented. 1925, in order to develop the economy of Central Asia, the motion of building Karakum water transfer project was put forward again. After a large number of experts' on-the-spot investigation, investigation and demonstration, the water transfer project was officially started on 1954. The goal of this project is to introduce the natural waterways of Amu Darya River and Syr Darya River into eastern Turkmenistan and central Uzbekistan to expand the irrigated land area. In particular, the Karakum Lenin Canal was built, starting from the Amu Darya River in the east (starting from Cerci), cutting off the water from the Amu Darya River in the upstream, and extending westward through Ashgabat, the capital of Turkmenistan, with a total length of 1400 km. This is a century-old project, and several generations of the Soviet Union have been working hard for it.

/kloc-After the completion of the two new canals in the 1960s, thousands of immigrants came to the Amu Darya River, Syr Darya River and the new canal basin, and 6.6 million hectares of paddy fields and cotton fields were reclaimed and irrigated, making this basin a new grain and cotton production base. Karakum Lenin Canal is the most important water transfer project, which can irrigate 3.5 million hectares of desert grassland and 6.5438+million hectares of newly reclaimed agricultural areas, and improve the water supply conditions of 7 million hectares of grassland. After the completion of the water transfer project represented by the new canal, cotton and rice have been harvested in this area, and agriculture has made great strides year after year. The annual output of crops has increased by four times compared with that before the construction of the water transfer project.

Then, the former Soviet Union built large-scale water diversion projects in Kazakhstan, Uzbekistan and Turkmenistan. The water sources of the Syr Darya and Amu Darya rivers in this area mainly come from the snowmelt in the distant mountains. These two rivers cross the Kizilkum Desert and finally meet at the bottom of the basin, forming the Aral Sea. However, after the completion of the diversion irrigation project, the water flows from the two rivers were diverted to the desert area to irrigate the farmland in the barren desert area to grow cotton and other crops. Although this river makes the desert full of vitality, it gradually dries up the Aral Sea.

By 1980, the annual output of cotton in the former Soviet Union reached 9.96 million tons, accounting for 20% of the world's total output, of which 95% was produced in this area. At that time, 40% of rice, 25% of vegetables, fruits and 32% of grapes in the whole Soviet Union were also produced in this area. The bumper harvest of agricultural production has promoted the economic development of this area, and the population has also increased rapidly, from 7 million in the early 1920s to more than 36 million. Through the transformation of nature, it has achieved unimaginable great gains, which is really a miracle on earth.

However, what people didn't expect was that agricultural production was bumper and regional economic prosperity didn't last long. The Aral Sea is an inland lake. When the flow of the Syr Darya and Amu Darya rivers drops sharply, the water level of the Aral Sea also drops sharply. According to the actual observation, from 197 1 to 1975, the inflow of the Syr Darya River and the Amu Darya River were 5.3 billion cubic meters and 21200 million cubic meters respectively, but from 1976 to 1980, it decreased to. From 198 1 to 1990, the total inflow of the Syr Darya and Amu Darya rivers is only 7 billion cubic meters per year. 1987 When the irrigated land increased to 7.3 million hectares, the Amu Darya River and the Syr Darya River were basically unable to deliver water to the Aral Sea, and the water level of the Aral Sea decreased by15m, the water area decreased from 66,000 square kilometers to 37,000 square kilometers, and the coastline retreated by150km. The Aral Sea has a surface area of only 25,200 square kilometers.

From 196 1 to 1970, the water level in the Aral Sea drops at a rate of 20 cm per year. In the 1970s, this speed reached 50-60 cm per year; In the 1980s, the speed reached 80-90cm per year. From 1960 to 2000, the amount of water pumped from the Amu Darya and Syr Darya rivers for irrigation doubled, and the corresponding cotton production doubled. From 65438 to 0987, the Aral Sea was divided into two parts: the North Aral Sea and the South Aral Sea; In 2003, the South Aral Sea was divided into East Aral Sea and West Aral Sea. In fact, the "Aral Sea" no longer exists, and several "small Aral Sea" that "fight alone" are in even more dangerous situation.

In the series of photos taken in 2000, the Aral Sea is only a part of 1960. The northern Aral Sea, sometimes called Little Aral Sea, has been completely separated from the southern Aral Sea. The South Aral Sea (the Great Aral Sea) has been divided into two parts, the east and the west, but the two parts can at least be connected by slender waters.

By 200 1, the connection between the two parts of the southern Aral Sea has also become a problem. The shallow waters in the east have shrunk rapidly in the past few years. From 2005 to 2009, the eastern waters of the South Aral Sea experienced the largest range of decline.

In 2005, in order to save the Aral Sea, Kazakhstan made a final effort to build a dam between the North and South Aral Sea. The construction of the dam is also equivalent to the death penalty for the southern Aral Sea. The water flowing from the Syr Darya River into the desert basin now only flows into the northern Aral Sea.

In 2005-2006, the water level in the northern Aral Sea rose obviously. The change of lake color is caused by the change of sediment.

From 2009 to 20 14, the water level in Aral Sea alternately experienced droughts and floods in different years. The dry climate in 20 14 years led to the first dry-up of the southern and eastern Aral Sea in modern times. 2 1 century, Kazakhstan and Uzbekistan announced a series of measures to save the fate of the Aral Sea, but their efforts did not fundamentally reverse the fate of the Aral Sea.

The Kazakh government took action to save the North Aral Sea. The government rebuilt the Syr Darya Canal, reducing the waste of water flow. In 2003, the government built another dam, blocking the circulation of the two parts of the Aral Sea to protect the North Aral Sea.

The recovery speed of the North Aral Sea is unexpected. The depth of the North Aral Sea has risen from less than 30 meters to 38 meters, and a reasonable depth of 42 meters is just around the corner. Today, the fishery production here has resumed, many fishermen have resumed their jobs that they once interrupted, and their fish have also been exported to Ukraine. This change may even bring cumulonimbus clouds that have not been seen for many years back to this area, bringing a glimmer of hope to the recovery of local agriculture. Due to the fiscal austerity of Uzbek government, the water level in the South Aral Sea is still falling. There is a lot of salt and sand in the exposed river bed, which greatly increases the sandstorm. Unfortunately, in 2003, the southern Aral Sea was divided into two parts, the East Aral Sea and the West Aral Sea, after the water level continued to drop. The salt content in their water has reached 0/00g per liter of water/kloc-,while the salt content in general seawater is only 35g per liter of water. The salt content in the East Aral Sea and the West Aral Sea is rapidly approaching the level of 300 grams per liter of water in the Dead Sea.

The Uzbek government decided to open the floodgates on the river regularly to let some water flow into the South Aral Sea.