Ahead of the Dushanbe International Water Forum, Tajikistan's President Emomali Rakhmonov echoed the hopes of cooperation which Central Asia's authoritarian governments have frequently voiced since the end of Soviet rule, but less frequently acted on.

"Water is our common heritage. It's necessary to ensure it is shared ... in a way that preserves it for future generations," Rakhmonov said in a written statement.

The ongoing evaporation of Central Asia's Aral Sea, once the world's fourth largest lake, has turned some 400,000 square kilometres into a toxic wasteland and symbolises wider concerns raised by recent United Nations research.

The UN's World Water Development Report estimates that some 2.2 million people around the world died due to water-related diseases last year.

Partly due to global warming, between two billion and seven billion people will be suffering from water scarcity by the middle of this century, the report warns.

But this deepening crisis "is essentially caused by the ways in which we mismanage water," the report reads. "The real tragedy is the effect it has on the everyday lives of poor people."

Impoverished Tajikistan may get a boost when delegates arrive from Canada, Lebanon, Turkey, Iran and the United States for the conference which starts Saturday, but few observers underestimate the scale of Central Asia's water problems.

They are particularly evident along the shores of the Amu-Darya River, which criss-crosses Uzbekistan and Turkmenistan's mutual border before trickling -- in a good year -- into what remains of the Aral Sea.

Amid a dearth of reliable statistics a leading non-governmental health organisation told AFP that tuberculosis and other diseases are on the rise among those in both countries scraping a living on the river's polluted shores.

Further north in Kazakhstan the damage to health and farmland caused by salt and poisonous dust carried on the wind from the sea's exposed bed is better documented.

At the root of the problem is a reluctance to reform a complex barter system seen as inflaming tensions between mountainous Tajikistan and Kyrgyzstan -- which have few natural resources except water -- and their water-thirsty cotton-growing neighbours downstream, Uzbekistan, Kazakhstan and Turkmenistan.

As elsewhere in the world critics point to a failure to listen to anyone beyond a few insiders.

Few people in Turkmenistan dare criticise autocratic President Saparmurat Niyazov's ongoing construction of a "Golden Century Lake" in the centre of his desert country, seen elsewhere as a white elephant project likely to add to the region's problems.

For its part Uzbekistan has often been accused of exerting disproportionate pressure on its neighbours, at times prompting fears that it is ready to use force.

"The Central Asian nations still approach the issue purely as an engineering problem," the Kyrgyzstan office of the International Crisis Group wrote recently. "Each country has started to view the problem as a zero-sum game."

Some reform efforts were announced recently at a meeting of four of the five Central Asian country's presidents, although Niyazov was absent, with international bodies like the World Bank likely to be called on for help.

But an Aral Sea rescue package intended for approval at this weekend's forum has been dropped from the agenda and there are worries that new demand for Central Asian water could come from neighbouring Afghanistan as it rebuilds its war-ravaged economy.

Tajikistan and Kyrgyzstan are keen to attract greater international attention to the issue.

"Rehabilitation work and investment are needed to help Afghanistan provide itself with enough water," Tajik Foreign Ministry spokesman Igor Sattarov said. "The drinking water problem is a global one."

SPACE.WIRE