Iraq is mostly desert and its inhabitable areas are slaked by the Tigris, which comes down from Turkey, the Euphrates, also from Turkey but passing through Syria, and a network of smaller rivers from Iran, some of which feed the Tigris.
Iraq accuses Turkey, and to a lesser extent Syria, of choking the Euphrates by placing hydroelectric dams on it that have restricted water flow, damaging an Iraqi agricultural sector already hit by decades of war, sanctions and neglect.
The dispute is a delicate diplomatic issue for Iraq as it seeks to improve ties with its neighbors and Turkey is one of Iraq's most important trading partners.
Saleh al-Mutlaq, leader of a Sunni Arab bloc in parliament, said he flew to Turkey on Friday and met Turkish Prime Minister Tayyip Erdogan and President Abdullah Gul to ask them to release more water from the river, which has been depleted by a drought.
"They have since increased the quantities of water coming to Iraq by 130 cubic meters per second," he said.
"It's not enough, but it has partly solved the water problems preventing our farmers from planting rice," he said.
That makes the flow of water to Iraq 360 cubic meters per second, up from the 230 cubic meters per second that Iraq received before Turkey took action.
Iraq's director of water resources, Oun Thiab Abdullah, said last week that Iraq faced a catastrophe this summer unless Turkey triples the Euphrates water flow. A drought has already withered crops and created severe water shortages. The river has dropped 35 percent since January, Abdullah said.
Iraq wants Turkey to let 700 cubic meters per second out, almost double what now flows through even after the increase.
Iraq's parliament voted last week to force the government to demand a greater share of water resources from neighbors upstream of its vital rivers, Turkey, Iran and Syria, turning up the heat on long running disputes.
They agreed to block anything signed with the nations not including a clause granting Iraq a fairer share of river water.
Turkish firms dominate northern Iraq's economy and Turkish firms have billions of dollars of contracts in Iraq.
Some 400,000 barrels of Iraqi oil a day -- more than a fifth of its exports -- are piped through the Turkish port of Ceyhan.