The wine waiter in a smart restaurant in São Paulo, Brazil’s economic powerhouse, holds up a bottle for his customers. He handles it as lovingly as a baby, then pours the wine into plastic cups. The pipes under the washbasins in the spotless toilets have been removed, so the water collects in bowls beneath and a notice asks customers to “please use this water to flush the toilets”. In the past few months this city of superlatives (the richest, most densely populated, with the most cars) has seen many such oddities. São Paulo has enjoyed the fastest economic growth of the past decade but now has a very severe water shortage.

São Paulo State (population 41 million) has been governed by the conservative Brazilian Social Democracy Party (PSDB) for the past 21 years. Water supplies were already very low last year and in October, when the issue was raised during…