VAKHDAT, Tajikistan (Reuters) - Under a scorching sun, an exhausted Tajik woman looks at a drying trickle of irrigation water running across her cotton field.
"Water is all we have," said Gulbakhor, a 55-year-old mother of nine, pointing at swathes of parched land stretching towards the austere mountains of central Tajikistan. She did not want to give her last name.
"But all the ponds and rivers are dry. We need to water our crop but we don't have enough even for ourselves."
Gulbakhor's despair, shared by millions of Tajiks in this tiny ex-Soviet nation north of Afghanistan, reflects a growing sense of alarm throughout Central Asia where stability depends on the region's scarcest and most precious commodity: water.
From tiny irrigation canals such as Gulbakhor's to the powerful Soviet-era hydroelectric plants, water is the source of misery and celebration in a poor region already overflowing with political and ethnic tension.
Central Asia is one of the world's driest places where, thanks to 70 years of Soviet planning, thirsty crops such as cotton and grain remain the main livelihood for most of the 58 million people.
Disputes over cross-border water use have simmered for years in this sprawling mass of land wedged between Iran, Russia and China. Afghanistan, linked to Central Asia by the Amu Daria river, is adding to the tension by claiming its own share of the water.
Water shortages are causing concern the world over, because of rising demand, climate change and swelling populations.
U.N. Secretary-General Ban Ki-moon has said water scarcity is a "potent fuel for wars and conflict."
Analysts say this year's severe weather fluctuations in Central Asia -- from a record cold winter to devastating spring floods and now drought -- are causing extra friction.
"Water is very political. It's very sensitive. It can be a pretext for disputes or conflicts," said Christophe Bosch, a Central Asia water expert at the World Bank. "It is one of the major irritants between countries in Central Asia."
In the Tajik village of Sangtuda, a scattering of huts in a dusty, sun-puckered valley near the border with Afghanistan, villagers showed their only source of water: a rusty pipe pumping muddy water from a Soviet-era reservoir.
"We are lucky. There are villages around with no water at all," said Khikoyat Shamsiddinova, an elderly farmer who said she had started planting drought-tolerant peas and watermelons -- a small boost to her household income.
Water scarcity is particularly painful for Tajikistan since its glaciers and rivers contain some of the world's biggest untapped water resources. A Soviet-era legacy of waste and decaying pipe networks are hampering sustainable distribution.
The World Bank, the European Bank for Reconstruction and Development and a host of European non-governmental organizations are helping Tajikistan build new canals and wells and repair the old ones.
Efficient water management requires advanced engineering expertise in water saving and resource planning in a region where most water simply vanishes into the ground if the irrigation timing is incorrect, experts say.
"If you look at quantity, yes, you have a lot of it, but it is not a question of quantity but quality and timing," said the World Bank's Bosch. "That's the problem in Central Asia."
The problems are having an effect far beyond farming. Lacking oil and gas reserves like some of its neighbors, Tajikistan depends on its sole Soviet-era hydroelectric plant, Nurek, to generate power.
Its crumbling power grid -- ruined by civil war in the 1990s -- finally gave out last winter, throwing hospitals, schools and millions of people into the dark and cold for weeks.
Makhmadnabi, a villager with a tired, weather-beaten faced, said people were becoming impatient. "The government must do something about it. People are gloomy," he said.
With a foreign debt worth 40 percent of the economy and state coffers empty, Tajikistan is unable to finance urgent sector reform, adding to discontent and potential unrest in an otherwise tightly run country where dissent is not tolerated.
"There is definitely a build-up of dissatisfaction," said one Western diplomat who asked not be identified because of the sensitivity of the issue. "People will have to go through another winter of dark and cold and then they will realize that something's wrong."
There have been no outward signs of anger, but the trend is a worry for Western powers watching the strategically placed country for signs of trouble.
In April, parliament urged Tajiks to give up half their wages in May and June to help finish construction of the $3 billion Rogun hydroelectric plant -- a project seen as key to solving energy shortages but which has been frozen since the fall of the Soviet Union in 1991.
"I urge all the patriots and sons of our land to take active part in constructing the first phase of the plant and add your contribution to the country's energy independence," Tajik President Imomali Rakhmon was quoted as saying in local media on May 31.
In Soviet days, water management was unified under Moscow's control, which linked Tajikistan and Kyrgyzstan, whose rivers and glaciers contain more than 90 percent of Central Asian water, with the arid plains of Uzbekistan, Turkmenistan and Kazakhstan.
The system fell apart when Soviet rule collapsed. With national rivalries on the rise, the new states have been unable to agree on how to share their water effectively.
Uzbekistan, Central Asia's most populous nation and a big gas producer, is angry that poor Tajikistan has the leverage to influence water levels in its cotton plains -- a powerful political tool.
Farmers in Kazakhstan, for their part, accuse Uzbekistan of dumping fertilizer in its rivers. Tajik officials complain that foreign investment in its hydroelectric sector has stalled because of fears of conflict with Uzbekistan.
A Chinese company pulled out of a project to build a power station on a Tajik river last year because of what Tajik industry sources said was China's reluctance to get involved in Central Asian bickering.
Observers agree that only cooperation between the five "stans" of Central Asia can provide sustainable water use.
"Countries should be able to do this as independent entities," said another Western diplomat, who also preferred not to be identified. "They're not children. They are grown-up members of the international community."