Water is a key resource in the otherwise arid Central Asian region, but since the Soviet Union's collapse Central Asian states have failed to find a successful regional approach for its management.

The three downstream states Uzbekistan, Turkmenistan and Kazakhstan need large amounts of water to irrigate their cotton and for other agricultural industries.

Upstream countries Tajikistan and Kyrgyzstan hold almost 80 per cent of Central Asia's water resources in their mountains and reservoirs. They complain that they have to pay top prices for energy supplies from their neighbours but are expected to get nothing for the water that flows out of their territory.

Both Tajikistan and Kyrgyzstan want to build hydroelectric plants but this could reduce the flow of water downstream.

Uzbekistan fiercely opposes such projects saying water is a natural product that cannot be denied to anyone.

In Soviet times a system of exchange enabled the five states to share water and energy resources such as electricity and gas. But the barter scheme is no longer active.

Russia, which has an interest in regional water resources, was not even invited to the forum.

Drought and overuse have caused an ecological disaster in the Aral Sea (pictured), which has shrunk by 90 per cent in recent decades.

What was in 1960 the world’s fourth largest lake now marks the boundary between Kazakhstan and Uzbekistan and is a shadow of its former self.

Starved of water as the Syr Darya and Amu Darya rivers were diverted to feed thirsty crops such as cotton and rice, the sea level has dropped by 20 meters.

In the late 1980s the Aral split into two parts, with the exposed areas largely covered in salt and toxic substances.