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It was once the world's fourth biggest sea, a vast lake in the middle of the Kyzylkum Desert.

However, a massive water diversion project begun by the Soviet Union in the 1960s has caused it to shrink dramatically - and this year, to dry up completely for the first time.

This series of images from Nasa's Terra satellite reveals the shocking change. 

Before the project, the Syr Darya and the Amu Darya rivers flowed down from the mountains, cut northwest through the Kyzylkum Desert, and finally pooled together in the lowest part of the basin. 

In the 1960s, the Soviet Union undertook a major water diversion project on the arid plains of Kazakhstan, Uzbekistan, and Turkmenistan. 

The region's two major rivers, fed by snowmelt and precipitation in faraway mountains, were used to transform the desert into farms for cotton and other crops. 

Before the project, the Syr Darya and the Amu Darya rivers flowed down from the mountains, cut northwest through the Kyzylkum Desert, and finally pooled together in the lowest part of the basin.

The lake they made, the Aral Sea, was once the fourth largest in the world.

Although irrigation made the desert bloom, it devastated the Aral Sea. 

This series of images from the Moderate Resolution Imaging Spectroradiometer(MODIS) on NASA's Terra satellite documents the changes. 

At the start of the series in 2000, the lake was already a fraction of its 1960 extent (black line). 

The Northern Aral Sea (sometimes called the Small Aral Sea) had separated from the Southern (Large) Aral Sea. 

The Southern Aral Sea had split into eastern and western lobes that remained tenuously connected at both ends. 

These images show the incredible changes in the region. Taken on August 15th 2001 (left) and August 19th 2014, they show the entire central area has dried up.

By 2001, the southern connection had been severed, and the shallower eastern part retreated rapidly over the next several years. 

Especially large retreats in the eastern lobe of the Southern Sea appear to have occurred between 2005 and 2009, when drought limited and then cut off the flow of the Amu Darya. 

Water levels then fluctuated annually between 2009 and 2014 in alternately dry and wet years. 

Dry conditions in 2014 caused the Southern Sea's eastern lobe to completely dry up for the first time in modern times.

As the lake dried up, fisheries and the communities that depended on them collapsed. 

The increasingly salty water became polluted with fertilizer and pesticides. 

The blowing dust from the exposed lakebed, contaminated with agricultural chemicals, became a public health hazard. 

According to NASA, the loss of the water's moderating influence has also led to more extreme temperatures in the region, making winters colder and summers hotter and drier. 

THE ARAL SEA

Aralsk's Mayor Alashbai Baimyrzayev points at a fishing boat on dry dock 23 March 1999 near the city of Kyzmet in the Aral Sea.

The Aral Sea is actually not a sea at all. 

It is an immense lake, a body of fresh water, although that particular description of its contents might now be more a figure of speech than practical fact.

Beginning in the 1960s, farmers and state offices in Uzbekistan, Kazakhstan, and Central Asian states opened significant diversions from the rivers that supply water to the lake, thus siphoning off millions of gallons to irrigate cotton fields and rice paddies. 

As recently as 1965, the Aral Sea received about 50 cubic kilometers of fresh water per year—a number that fell to zero by the early 1980s. 

Consequently, concentrations of salts and minerals began to rise in the shrinking body of water.

The Aral Sea supported a thriving commercial fishing industry employing roughly 60,000 people in the early 1960s. 

By 1977, the fish harvest was reduced by 75 percent, and by the early 1980s the commercial fishing industry had been eliminated. 

The shrinking Aral Sea has also had a noticeable affect on the region's climate. 

The growing season there is now shorter, causing many farmers to switch from cotton to rice, which demands even more diverted water.

A secondary effect of the reduction in the Aral Sea's overall size is the rapid exposure of the lake bed. 

Strong winds that blow across this part of Asia routinely pick up and deposit tens of thousands of tons of now exposed soil every year. 

The salty dust blew off the lakebed and settled onto fields, degrading the soil. Croplands had to be flushed with larger and larger volumes of river water. 

The loss of the moderating influence of such a large body of water made winters colder and summers hotter and drier.

In a last-ditch effort to save some of the lake, Kazakhstan built a dam between the northern and southern parts of the Aral Sea. 

Completed in 2005, the dam was basically a death sentence for the southern Aral Sea, which was judged to be beyond saving. 

All of the water flowing into the desert basin from the Syr Darya now stays in the Northern Aral Sea.

Between 2005 and 2006, the water levels in that part of the lake rebounded significantly and very small increases are visible throughout the rest of the time period. 

The differences in water color are due to changes in sediment.