This UK premiere asks if a mega-city can mobilize its' 22 million citizens to become water sustainable. Mexico City was built not near water but in the middle of a lake. To supply the city with fresh water is such a task that it has become compulsory to bring water from other states. In addition once sewage water leaves the city it ends up in agriculture. The environmental documentary details in a gripping way the daily struggle of the Valley of Mexico as it tries to save itself while its population grows.