India, April 17 -- At over 8,000 people per sq km, Singapore is one of the most densely populated countries in the world.

About 30% of the island nation lies less than 5 metres above sea level, making it vulnerable to rising sea levels. It has no natural aquifers or large freshwater lakes and draws up to 50% of its water supply from neighbouring Malaysia, in an agreement that stands to expire in 2061.

Meanwhile, as the population and economy grow, water demand is expected to almost double by 2065.

The country has been working to address this potential crisis since 2003.

The initiative is called NEWater. It consists of recycling and purifying wastewater to high standards, then sending it into reservoirs, where it mixes with the natural...