SHANGHAI Shanghai means 'above the sea'. The world's largest port city is located on the East China Sea and is split in two by the Huangpu River. The old centre Puxi is on the western bank, and the modern financial centre Pudong is to the east. With hundreds of skyscrapers, this is one of the most famous skylines in the world. Shanghai is about four metres above sea level. But for howmuch longer? More than 24 million people live and work in this city, which has expanded spectacularly. Breathakingly rapid urbanisation of this kind is never without problems. For example, more and more groundwater was pumped up to meet demand for water from the inhabitants. Since 1921, the city has subsided at least two metres. As a result of restrictions on groundwater extraction in the 1960s, Shanghai is now subsiding by 'only' seven millimetres a year. Land subsidence makes floodingmore likely but it can also be the indirect cause of damage to infrastructure. For example, large holes can open up in roads. It is estimated that land subsidence in Shanghai resulted in economic damage amounting to two billion dollars between 2001 and 2010. Shanghai is an example of a city where land subsidence can be controlled with sophisticated groundwater management. In addition, urbanisation is also taking its toll on soil and groundwater quality in Pudong. Pollution with heavymetals or organic pollutants is a threat to the health of crops and people. Deltares advises cities about land subsidence and helps local businesses to clean up soil in sustainable ways.