A Mexican non-profit group is helping residents of Mexico City – where roughly a million people lack access to the municipal water supply – to harvest rainwater that falls on their roofs. One such resident, Edgar Serralde, who lives in the Xochimilco district, says he can save six times more water than he used to be able to collect in barrels. His new system filters the water and stores it in a 5,000-litre cistern. Serralde had to pay less than 20% of the $900 (£730) cost, with the non-profit, Isla Urbana, covering the rest.

Some Mexico City residents see future in rain harvesting – Daily Mail