The sources

The Water Needed to Have the Dutch Drink Coffee

Chapagain, A.K. and Hoekstra, A.Y · UNESCO-IHE / Water Footprint Network · 2003

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The coffee comparison in the water chapter comes from here: roughly 140 litres of water across the supply chain for a small cup.

Cited in

Chapagain, A.K. and Hoekstra, A.Y. The Water Needed to Have the Dutch Drink Coffee. UNESCO-IHE / Water Footprint Network, 2003. (Roughly 140 litres per 125 ml cup.)