Indian residents in a district facing a drinking water shortage wait with plastic pots at a community tube well to collect drinking water in Bangalore on October 8, 2012. (Manjunath Kiran/AFP/Getty Images)

Valan, a rice farmer in a starched white shirt and sarong, walked along the bone-dry canal bed next to his village in the state of Tamil Nadu as though it were a road. The canal should have been full from last June until the end of the year, he said, but it stood dry, except for one month in which unexpected storms flooded the canal and destroyed his crops.

In the past, “we could just use the rainwater,” said Valan, who like many Tamils has only one name. “But the rains are becoming more unpredictable, so certainly the river is becoming more important.”

Valan was referring to the Cauvery, a 475-mile river that supports farmers in three southern Indian states. After the poor monsoon last year, the river became the subject of a bitter legal battle that drew in the nation’s Supreme Court and ended only in February with a federally mandated water-sharing deal between Karnataka, the state in which the Cauvery begins, and Tamil Nadu, its downstream neighbor.

As India’s economic growth drives a rising thirst for water, and with its annual rainy season projected to become increasingly erratic in coming years because of climate change, many states across the country are fighting over their shared rivers. In the west, a tribunal has been working since the fall to find a solution to three states’ claims on the Mahadayi, or Mandovi, River. Another tribunal is trying to solve two eastern states’ dispute over the Vansadhara.

There are similar tensions on an international level. Manmohan Singh, India’s prime minister, last week asked China for more openness about its plans to build dams on the Brahmaputra, a vast Himalayan river that flows into India from the Tibetan region of western China.

India’s river disputes “have become more severe, and they will continue to become more severe,” said Ashok Jaitly, who sits on a national government committee that is drafting a law on water management. “Water use is increasing, but the supply is fixed.”

With India ruled by a fractious coalition government, state-level spats can destabilize national politics. The dynastic Congress party, which leads the coalition, controls fewer than half of the country’s 28 states and relies on alliances with regional parties, which often put local and populist causes first. The river disputes are one such example, said Tushaar Shah, a senior fellow at the International Water Management Institute, a research group headquartered in Sri Lanka. “I do think [the disputes] are getting worse. It’s become a political issue, and state politicians are always playing to the galleries.”

One regional party from Tamil Nadu recently left the Congress-led coalition after the federal government refused to alter foreign policy to fit its demands.

India will need 1.5 trillion cubic meters (396 trillion gallons) of water per year by 2030, about double its existing supply and more than a fifth of the projected global demand, according to a 2010 report from the International Finance Corp. and the consulting firm McKinsey & Co. Yet as the population swells, India’s water supply per person is dropping. The country has an annual average of 1,545 cubic meters (408,145 gallons) of water available per person, according to India’s 2011 census — qualifying it as a “water-stressed” nation under World Bank criteria.

That growing thirst is driven by agriculture, with about 90 percent of the country’s water used in farming. India, home to 1.2 billion people and set to overtake China as the world’s most populous country by 2025, has a surging demand for food. Rice, a national staple, requires up to 1 million gallons of water per acre — double the amount needed for wheat.

Rising incomes also mean that more people can afford costly and water-intensive items such as meat and dairy products. New factories and thermal power stations are further pushing up water usage.

Wasted water

In Tamil Nadu, rain shortfalls before and after a bout of damaging storms caused almost half the crops in the 1.6 million-acre Cauvery delta — an area known as South India’s rice bowl — to fail or to produce low yields during January’s harvest, according to the delta’s farmer welfare association.

Magizhi’s farmers are getting by on government handouts. They say they have received about $184 per acre of failed crops. The state government is also distributing free rice from its grain stores.

After its complaints last year that Karnataka was diverting water from the Cauvery, Tamil Nadu recently also asked the federal government to stop the neighboring state from diverting water from the Ponnaiyar, another interstate river, according to local newspaper reports.

However, even as India’s states fight over their rivers, experts say that there is enough water to go around but that much is being wasted. Farmers, who account for more than half the population and constitute a vital voter bloc, receive irrigation subsidies and use cheap water imprudently, experts say.

“The traditional farmers think that the government has a responsibility to give them water, and they don’t take care to use it efficiently,” said S. Ranganathan, the general secretary of the delta’s farmer welfare association, though he added that many farmers are adapting.

In urban areas, rivers and lakes near booming but unplanned cities are often contaminated. Shah, the International Water Management Institute senior fellow, said India’s problems with water availability are “being overplayed.”

“It’s more to do with how you manage the water than how much you have,” he said. “There are many countries that are doing much better with less water, such as the Middle Eastern countries.”

Some Indian states are starting to encourage or compel efficiency, Shah said. Karnataka has raised water prices in some cities. Gujarat, a western state, has limited farmers’ access to electricity for irrigation pumps to eight hours a day. But with a dozen states facing votes this year or the next, and a national election due by May 2014, politicians are unlikely to enact more curbs that affect farmers.

Erratic monsoons

Ranganathan said the Cauvery dispute is far from finished. Although the spat between Karnataka and Tamil Nadu had been rumbling at a low level for several decades, he said, it is likely to keep flaring up in the coming years as India’s rainy season becomes more erratic.

The annual monsoon on which India’s farmers depend is becoming more unpredictable, according to rainfall data for 1901-2004. A mix of dry spells and sudden downpours, rather than the traditional uninterrupted weeks of rain, is becoming more common.

Environmentalists have warned for years that India is particularly at risk from such phenomena, which they link to global warming. “The Himalayan glaciers are receding, agricultural yields are stagnating, dry days have increased, patterns of monsoon have become more unpredictable,” Jairam Ramesh, the minister of environment and forests at the time, told the Mint newspaper in 2009. “So, we are seeing the effects” of climate change.

As for this year’s water-sharing pact, the problem “is that it does not contain a formula for sharing water in situations of distress — when the monsoons fail,” Ranganathan said. “But there is every chance that the idea of distress will become a permanent part of how we share out the water.”