Petrolina occupies the southernmost tip of Pernambuco, on the left bank of the Sao Francisco River at 376 metres above sea level. Directly across the water sits Juazeiro, in Bahia — a different state, a different time zone of local politics, and functionally the same city. The Presidente Dutra Bridge ties them together, and together they form an urban area of nearly 700,000 people that Brazilian planners formally recognise as an integrated development region.\n\nThe river they share is Velho Chico, Old Chico, 2,830 kilometres of it and the longest river running entirely inside Brazil. It is called the river of national integration for a reason: it drains out of Minas Gerais in the southeast and carries water across five states into a Northeast that has very little of its own. Petrolina began as Passagem de Juazeiro — the Juazeiro crossing — and became a municipality in its own right in 1893, raised to city status in 1895. Where the name came from is genuinely unsettled. One account credits the emperor Pedro I and his empress Leopoldina; another says it comes from a handsome rock on the riverbank.

Twenty-six kilometres upstream, the Sobradinho Dam was completed in 1979 and impounded one of the largest artificial lakes on Earth — a reservoir covering 4,214 square kilometres and stretching 400 kilometres up the valley, the thirty-fifth largest in the world by volume. It regulated a river that had run to its own erratic schedule and made year-round irrigation possible in soils that had never supported anything more ambitious than cattle and subsistence plots.\n\nFederal development policy had been building toward this since the 1960s: highways, rural electrification, sanitation. What followed the dam were the irrigation perimeters — Bebedouro first, then the vast Senador Nilo Coelho scheme — and behind them the processing plants for tomato paste, juice and textiles. The transformation was not gentle or evenly distributed, but it was total. A landscape of extensive ranching became a landscape of geometric green blocks.

The numbers are hard to credit. Growers in the Petrolina-Juazeiro nucleus account for roughly 90 percent of Brazil's mango exports and 30 percent of its table grapes, having displaced Sao Paulo and Rio Grande do Sul as the country's leading exporters of both. In 2012 alone, Petrolina's vineyards produced 153,450 tonnes of grapes from 4,650 hectares, and its orchards 173,800 tonnes of mangoes from 7,900 hectares.\n\nAlongside them come bananas, coconuts, guavas, passion fruit, melons, industrial tomatoes, watermelons and onions for the domestic market. The export fruit leaves by air. Senador Nilo Coelho International Airport handles regional passenger flights to Recife, Salvador and Sao Paulo alongside international cargo runs of fresh fruit — table grapes and mangoes picked in the sertao and sold in Europe and the United States without ever having been refrigerated into anonymity.

Serious viticulture arrived in the 1980s, and Petrolina now ranks as Brazil's second most important wine centre. Nothing about the setting is conventional. This is nine degrees south of the equator in a hot semi-arid climate, where the vines are irrigated and never experience the cold dormancy that structures the growing year in every classic wine region. The fruit ripens under continuous heat stress, which gives the wines of the Sao Francisco valley a character that has nothing in common with Brazil's cooler southern vineyards in Rio Grande do Sul.\n\nThe region hosts an international wine competition, which for a place that had no wine industry within living memory is a reasonable measure of how fast the valley has moved.

Prosperity here is real and it is unevenly held. In 2010, 20.9 percent of Petrolina's population — around 60,123 people — lived below Brazil's official poverty line, and 8.3 percent below the line of extreme poverty. The Gini coefficient stood at 0.6253, high even by Brazilian standards. The proportion in poverty had fallen sharply since 2000, which is the honest other half of the sentence.\n\nThe climate has not changed either. Rain is supposed to fall between November and April, and in many years very little falls even then. The surrounding caatinga was designated a conservation priority when the Caatinga Ecological Corridor was created in 2006 — an acknowledgement that the thorn forest being converted into orchard is itself a biome found nowhere else. Petrolina is a city of roughly 418,000 people built on the proposition that engineering can outrun drought. So far it has.