Unchecked development, and the widespread, unregulated pumping of groundwater throughout Siem Reap city, has raised concerns that the temples, including the world's largest religious monument, Angkor Wat, could crack or crumble if too much water is drained away.

The temples and towers of the 402-square-kilometre Angkor site sit on a base of sand, kept firm by a constant supply of groundwater that rises and falls with the seasons, but which is now being used to supply a burgeoning city.

With the number of visitors to the northern Cambodian province approaching 2 million a year, increasing pressure is being put on the scarce water resource.

Thousands of illegal private pumps have been sunk across the city, pulling millions of litres of water from the ground each day.