EL PRAT DE LLOBREGAT, Spain: Where once the population of Barcelona drank mostly from its rivers and wells, Spain's second city now relies upon a labyrinth-like mesh of green, blue and purple pipes inside an industrial plant to keep it from going thirsty amid a prolonged drought.

Water is pumped from two kilometers (1.2 miles) into the Mediterranean Sea to where the Llobregat desalination plant sits on an isolated stretch of beach. After journeying through several cleaning and filtering systems it reaches its final stop: the twisting and turning multi-colored channels that squeeze every drop of water free of its salt.