The World Bank has released a report saying the the worst effects of global warming will be felt in the world's water supplies.  And it suggests that inadequate water supplies will knock as much as six percent off of the Gross Domestic Product (GDP) of some regions by the year 2050.

And that sets up a vicious cycle, since these worst-hit nations in the Middle East, South and Central Asia, and Africa will need large amounts of money to deal with the crises.  And some nations will see several years of negative growth.

"When we look at any of the major impacts of climate change, they one way or another come through water," said World Bank economist Richard Damania, the lead author of the report, titled "High and Dry: Climate Change, Water and the Economy".  He says,"It will be no exaggeration to claim that climate change is really in fact about hydrological change."

If the world's current water management policies are maintained, the Middle East GDPs would lose 14 percent; the semi-arid region of Africa just south of the Sahara Desert would lose 12 percent; Central Asia could lose close to 11 percent of GDP, and East Asia about 7 percent.  North America and Europe would see no change.

The World Bank report says that 1.6 billion people on Earth already live in nations that are subject to water scarcity, but worries that number could double in the coming decades. 

However, it is not too late.  If countries get their acts together and make more efficient use of water, it would add more than 11 percent to the GDP of central Asian countries and blunt the impact of water shortages in the Middle East, the report found.