By Henry Mance
Water from the Sao Francisco keeps Emanoel de Souza's rice field fertile
Outside his house by the Sao Francisco river, Emanoel de Souza toys with the skin of a caiman he hunted a month earlier.
"There are plenty out there. You leave a cow's heart on a hook by the river, and by morning a caiman will have bitten," he smiles.
The meat makes for a good meal and the skin provides an amusing decoration.
But Mr de Souza gets much more than caimans from the Sao Francisco.
The river also provides water for him to farm fish and rice. The profits of the last harvest alone paid for a new motorbike.
This makes him one of the lucky ones. Just a few kilometres away, out of reach of the Sao Francisco's water, Raquel Torres has lost a crop of beans and maize due to lack of rain.
"This is the second consecutive year. There is no irrigation here," she says.
The water she uses for drinking, cooking and washing arrives every few weeks by lorry. Like many residents of Brazil's dry north-east, she knows that water can be the scarcest commodity.
The national government's solution is to divert part of the Sao Francisco - the only major river that starts and finishes in Brazil - through the sertao, the semi-arid backlands.
Two large canals, one of 400km and another of 220km, will deliver water to cities and to agriculture.
Brazil's government says the canal water will benefit 12 million people
The basic idea is not new - it has been mooted for centuries and seriously mulled over for decades - but its implementation is.
Works began in 2009 and are scheduled for completion in 2025. Then, the government claims, the project will benefit more than 12 million "people who are thirsty".
And the north-east feels thirsty. Looking over the potentially fertile soils of the sertao under the intense sun, locals are prone to echo a single sentiment: all that is lacking is water.
They point to the example of Petrolina, a nearby city that, thanks to irrigation, has become one of Brazil's leading producers of fruit for export. Indeed, it is the only place in the world where grapes can be harvested twice a year.
Not everyone is so optimistic. Environmentalists say the Sao Francisco is already overused.
The current project, they say, threatens the river's capacity to generate the North East's hydroelectricity, as well as the livelihoods of those who, like Emanoel de Souza, currently depend on it for agriculture.
Fresh meat is not the only benefit farmers gain from the river
"The diversion won't resolve the water supply problem of the most-at-need people in the sertao, because they are geographically so spread out," argues Joao Suassuna, a long-time critic.
"And the Sao Francisco River, because it has multiple uses, won't be able to supply the volumes of water necessary to ensure the viability of the venture."
Instead he points to a 2005 study, the North East Atlas, which concluded that reservoirs and rainfall could supply three times as many people as the diversion, for about half the cost.
Both supporters and opponents of the diversion project agree that, when it comes to the north-east and water, technical arguments only explain so much.
The diversion project is as much political as it is agronomical. For President Lula da Silva, it is his chance to show his commitment to his native north-east.
Flow of capital
For the north-east, it promises enormous investment: at 6.6bn reais ($3.7bn), the biggest single project of the current government.
For Mr Suassuna, such political considerations have meant inefficiency. "The government chose the more expensive project [the diversion], just so that more resources could be dedicated to the north-east," he says.
The work to divert the Sao Francisco river begins here at Cabrobo
But others see it as a blow for the north-east against the richer, more influential south.
"For people from the south, we are like what Brazilians are for Americans: third-class. We are profoundly discriminated against," says Eudes Caldas, mayor of Cabrobo, where the diversion works are taking place.
Cleiodezio Goncalves, owner of a hardware store in Cabrobo, shares the mayor's enthusiasm. Having lived his whole life in the sertao, he is all too familiar with its stalled economic progress.
He did not see a car until he was 18; now a stream of construction trucks rolls by just a few blocks away.
Cleiodezio Goncalves says diverting the river will bring jobs
"I'm in favour of the diversion," he says. "Many people have now got work here. Before, the young people were getting into drugs."
And yet, beneath the enthusiasm, doubts often lie about the details of the diversion
"Some say there will be water, others that there won't be. You're left in doubt," says Raquel Torres.
Even Mayor Caldas complains that the federal government should do more for his town, not just those further up the line.
"The diversion is here, the consequences are here," he says, arguing that a 5km stretch of land expropriated by the government could be handed over to local producers.
What is clear is that water is in the political limelight. Earlier this year, President Lula and his party's candidate in November's presidential election, Dilma Rousseff, travelled to Salitre, on the opposite bank of the Sao Francisco, to inaugurate a separate irrigation project.
At the event, the president himself was theatrical. "Stop filming me, and start filming the water. Look how beautiful it is!" he told the assembled press.
Ms Rousseff was more sober, speaking of the needs of small producers.
She is likely to face Sao Paulo Governor Jose Serra in November's poll. He is the only major candidate not to have explicitly committed himself to Sao Francisco project.
Water means much in the north-east - and Ms Rousseff is hoping it might mean electoral buoyancy.