Zhang Baishan has one of the toughest jobs in China.

Mr Zhang wears the uniform of the Chinese bureaucrat – black loafers, black trousers, black windbreaker – but he does more than push papers. The 56-year-old is in charge of making sure that the provinces along China’s most important river stick to an agreement to share its water, a task that is growing harder as the country’s industrial growth outpaces its resources.

In his efforts to control the Yellow River Mr Zhang is heir to a mythical engineer called Yu the Great, who first tamed the river 4,000 years ago. But while Yu laboured to manage floods, Mr Zhang’s challenge as director of water resources management at the Yellow River Conservancy Commission is to keep the world’s sixth-longest river from running dry.