To head off the "extremely grave" situation, India's government needs to dramatically change the way it manages water, such as decentralizing management of water supplies and linking rivers, said John Briscoe, who authored a World Bank report released Wednesday on the country's water resources.

Demand for water is increasing rapidly because of India's growing population -- already above 1 billion -- and high economic growth.

But increased demand has not been matched by efforts to conserve and better manage water supplies, meaning that the resource is being depleted faster than it can be replenished, Briscoe said.

The report predicted that availability of surface and ground water would decline to less than 80 cubic kilometers (2.8 million cubic feet) in 2050, from about 500 cubic kilometers (17.6 million cubic feet) now.

"Fifty years, in water management, is a blink of the eye," Briscoe said. "It is an extremely, extremely grave situation."

Making matters worse, he said, "there is widespread complacency in the government."

Indian officials did not immediately comment on the report.

About 15 percent of the country's aquifers are already in critical condition, a number that could increase to 60 percent by 2030, he said.

Briscoe said the problem is more serious for some states, such as Punjab, Haryana and Rajasthan in northern India and the southern states of Tamil Nadu and Karnataka.

In all five states, farmers are using large amounts of groundwater because they can't get enough from canals and rivers.

Heavily subsidized electricity for farmers in these states also encourages them to switch to groundwater, which can be cheaply siphoned with electric pumps, Briscoe said.