What was known as history's fertile crescent, where lush farmland and abundant water gave rise to civilisation, is today a dusty desert where the Tigris and Euphrates rivers crawl sluggishly toward the sea.

Vast tracts of Iraqi farmland are cracked and barren, precious marshes have dried up and sandstorms blot out the sun.

Even Saddam River, the flagship drainage system Saddam Hussein launched in the 1980s to restore Iraq to its ancient agriculture glory, has turned into a sickly green stream flowing far below its high-water mark.

Such are the symptoms of a worsening water shortage that threatens to undermine Iraq's efforts to rebuild its economy after six years of war unleashed by the 2003 invasion.

Water is such a precious commodity in the arid Middle East that many experts predict water wars in the future if a sustainable solution is not found.

Tensions intensified earlier in the month when Turkey announced that it would resume work on its controversial plan to build a hydroelectric dam on the Tigris in its southeast.

Citing cultural and environmental standards, European backers have pulled support for the Ilisu dam project, a temporary victory for Baghdad, but Ankara is determined to push ahead as it seeks to wean itself off energy imports.

"This is not a new crisis for Iraq, but this time it's more serious than ever before," said Amro Hashim, an economic expert at Baghdad's Mustansiriya University.

Iraqi politicians are quick to blame upstream neighbours Turkey, Iran and Syria for dams and increased usage, but experts say Iraq's problems are also rooted in an exploding population, inefficient irrigation and few incentives to conserve water.

"It's everything going on at once. It's the urbanisation, it's the climate change, short-term variability in climate, increased demand for food," said David Molden, deputy head of the International Water Management Institute in Sri Lanka.

"Iraq is one place, but it's not alone in the world ... Yes you can always blame neighbours or climate change but ultimately we've got to change the way water is managed," he said.

Iraq is now in the second year of a major drought, and last year's use of reserves has made for the worst water shortage in a decade, US officials in Baghdad say. Drought may bring one of the worst wheat crops in a decade, as low as 1.35 million tonnes or around half a normal crop, a dramatic reversal for a nation that was once a regional grains supplier but which now ranks among top world wheat importers.

It's not just a lack of water that has made Iraqi agriculture so anaemic, says Salah Faisal, a farmer bracing himself for reduced harvest on his farm south of Baghdad.

"In the 1980s it was war with Iran, in the 1990s it was Kuwait and now it's the Americans. There are five to six million martyrs and 70 per cent of the people in the countryside have fled. What do you expect?" he asked, squinting beneath the scorching summer sun.

Trouble for Iraq's farm sector, the largest employer but dwarfed by oil in economic output, equals trouble for Iraq.

Dependence on food imports, depopulation of the countryside and a fear that idle youth may be recruited as insurgents are factors behind a special initiative launched by Prime Minister Nuri al-Maliki to revive the moribund farm industry.

Yet results will be slow as officials nudge farmers to abandon practices such as flood irrigation, which over time has boosted soil salinity and helped make farmland less fertile.

In the absence of proper drainage, Iraqi waterways are dangerously salty. The salinity level of water flowing into Iraq is 400 parts per million (ppm). When it reaches the Gulf, that has risen to 2,000 ppm, the Agriculture Ministry says.

That compares to around 1,000 ppm in America's Colorado river at its outfall, Mr Molden said. "Most crops, except the most salt tolerant crops, will drop in productivity from their potential when irrigated with this water."

In Baghdad, mud banks sprouting fields of reeds now rise out of the slow-moving Tigris, a far cry from 20 years ago when schoolchildren took a swim in its swift currents at their peril.

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