Many residents only have to sniff the tap water to know something is not right.

"I fear giving it to my children directly unless I boil it," said Enam Mohammed Ali, a 36-year-old mother of four in the New Baghdad district in the eastern part of the city.

Two-thirds of the raw sewage produced in the capital flows untreated into rivers and waterways.

In some Baghdad neighborhoods, notably New Baghdad and Baladiyat, the Tigris is so filthy with sewage and other pollutants that the local treatment facility can only do so much. To make matters worse, sewage then leaks into the potable water pipes.

A cholera outbreak in northern Iraq last year killed 14 people. A similar outbreak of the waterborne disease in Baghdad — home to about 6 million people — could be far worse.

"Iraq is on the cusp of a serious water crisis that requires immediate attention and resources," said Thomas Naff, a Middle East water expert at the University of Pennsylvania.

The World Bank has estimated that it would take $14.4 billion to rebuild the Iraqi public works and water system.

Iraq has been slow in spending its billions in oil revenues on public works projects.

"Up to now we have seen nothing from the government," Sheik Ayad Abdul-Jabbar al-Jubouri complained.

Mustafa Hamid, a spokesman for the Iraqi environment ministry, said the water pipe network is more than 50 years old and suffers from corrosion "which allows sewage water to infiltrate."

But Hamid downplayed the risk. "There is contamination but not a serious one," he said, saying test results in most parts of the city generally met "safe standards."

Many residents are unconvinced.

Hassan Khalid, 13, said he took antibiotics for typhoid four months ago after drinking tap water. "I had fever, headaches and was throwing up all the time," he said.

Although bottled of water is sold in Iraq — much of it from Saudi Arabia — the majority of Baghdad residents use tap water. US troops, however, are warned that the water is only for bathing, not drinking.

A US Embassy official said she has seen black sewage water gushing into the Tigris from a giant pipeline during an aerial tour.

Farmers in Baghdad's northern districts of Azamiyah and Istiqlal, just a few miles from the Tigris, are forced to use sewage water to irrigate crops.

The Tigris, which cuts through the heart of the capital and provides most of its drinking water, runs brownish green in the summer. But it still attracts bathers seeking to escape the scorching heat.

"The water smells like dead fish," Giya Nouri, a 40-year-old construction worker, said as he swam with his two young sons. "When I was a kid, it was blue and clean."

So far there has been no outbreak of waterborne diseases in Baghdad.

Last year in Iraq, the World Health Organization confirmed more than 3,300 cases of cholera, a gastrointestinal disease typically spread by contaminated water, and at least 14 deaths from the acute and rapid dehydration it causes. The hardest hit areas were in northern Iraq.

Dr. Nagesh Kumar, a water expert in India, said Iraq's current drought "will make the water contamination situation worse" by drying up wells and lowering river levels.

In the capital, the Tigris is at its lowest level since 2001. Reeds stick up from the water on each bank.