When it rains, this patch of green becomes a natural filter, catching soil contaminants from surface runoff, thus producing cleaner water which will be cheaper to treat when the water reaches the reservoirs later.

Called a 'rain garden' by its creator, the national water agency PUB, the 0.6ha plot has 14 plant species growing in a blend of coarse sand and fine gravel.

Read the full version of Tania Tan's story in Tuesday's edition of The Straits Times.