<P> This was part of the Soviet plan for cotton, or "white gold", to become a major export . This temporarily succeeded, and in 1988, Uzbekistan was the world's largest exporter of cotton . </P> <P> The construction of irrigation canals began on a large scale in the 1940s . Many of the canals were poorly built, allowing water to leak or evaporate . From the Qaraqum Canal, the largest in Central Asia, perhaps 30 to 75% of the water went to waste . Today, only 12% of Uzbekistan's irrigation canal length is waterproofed . Of the 47,750 km of interfarm irrigation channels in the basin, only 28% have anti-infiltration linings . Only 77% of farm intakes have flow gauges, and of the 268,500 km of onfarm channels, only 21% have anti-infiltration linings, which retain on average 15% more water than unlined channels . </P> <P> By 1960, between 20 and 60 km (4.8 and 14.4 cu mi) of water each year was going to the land instead of the sea . Most of the sea's water supply had been diverted, and in the 1960s, the Aral Sea began to shrink . From 1961 to 1970, the Aral's level fell at an average of 20 cm (7.9 in) a year; in the 1970s, the average rate nearly tripled to 50--60 cm (20--24 in) per year, and by the 1980s, it continued to drop, now with a mean of 80--90 cm (31--35 in) each year . The rate of water use for irrigation continued to increase; the amount of water taken from the rivers doubled between 1960 and 2000, and cotton production nearly doubled in the same period . </P> <P> The disappearance of the lake was no surprise to the Soviets; they expected it to happen long before . As early as 1964, Aleksandr Asarin at the Hydroproject Institute pointed out that the lake was doomed, explaining, "It was part of the five - year plans, approved by the council of ministers and the Politburo . Nobody on a lower level would dare to say a word contradicting those plans, even if it was the fate of the Aral Sea ." </P>

What caused the dramatic reduction to the aral sea in former soviet union