The world is heading toward "water bankruptcy" as demand for the precious commodity outstrips even high population growth, a new report warned Friday.

In less than 20 years water scarcity could lose the equivalent of the entire grain crops of India and the United States, said the World Economic Forum report, which added that food demand is expected to sky-rocket in coming decades.

"The world simply cannot manage water in the future in the same way as in the past or the economic web will collapse," said the report.

Water has been consistently under-priced in many regions and has been wasted and overused, the report said.

Many places in the world are on the verge of "water bankruptcy" following a series of regional water "bubbles" over the past 50 years.

The report said that energy production accounts for about 39 percent of all water used in the United States and 31 percent of water withdrawals in the EU. Only three percent is actually consumed, but competition for access to water will intensify over the next two decades.

Water requirements for energy are expected to grow by as much as 165 percent in the United States and 130 percent in the EU, putting a major "squeeze" on water for agriculture, said the WEF.

The report said most glaciers in the Himalayas and Tibet will be gone by 2100 at the current rate of melting, but they provide water for two billion people. About 70 major rivers around the world are close to being totally drained in order to supply water for irrigation and reservoirs.

The WEF said that within two decades water will become a mainstream theme for investors -- even better than oil.

Speaking at the Davos forum on Thursday, UN Secretary General Ban Ki-moon said: "The water problem is broad and systemic. Our work to deal with it must be so as well."

Corporate chiefs at the forum have also expressed concern. "I am convinced that, under present conditions and considering the way water is being currently managed, we will run out of water long before we run out of fuel," said Peter Brabeck-Letmathe, chairman of Swiss food conglomerate Nestle.

"The only way to measurably and sustainably improve this dire situation is through broad-scale collaborative efforts between governments, industry, academic, and other stakeholders around the world," said Indra Nooyi, chairman and chief executive of PepsiCo Inc, the US drinks major that makes huge use of water.

Dominic Waughray, the WEF head of environmental initiatives, said "management of future water needs stands out as an urgent, tangible and fully resolvable issue for multiple stakeholders to engage in."