>340 to 620 litres I amused myself trying to find the source. The article is based from a quote from the book which is based on a study: The green, blue and grey water footprint of crops and derived crop products, Twente Water Centre http://waterfootprint.org/media/downloads/Mekonnen-Hoekstra-... I think he is for example counting the rain and irrigation water that falls on the sugar cane that it used to make the Cok…
Really, the only thing wasteful would be the energy needed to pump up and distribute the water. But we get some of the most efficient farmland in return, without harming anyone (unlike e.g. the US that caused the dustbowl thanks to overly aggressive farming)
edit: also that's only when irrigation is actually needed, we get our fair share of rain.