Catching the Rain on a City
Terry Thomas
Urbanicity, City Matters magazine, 2002
Cities receive rainfall but also import other water by pipe, river, aquifer and bottle from outside their borders. They export water via storm drains and foul drains near the surface, via the soil beneath them and (via the leaves of plants) to the air above them. These exchanges are often rather unsatisfactory. There are sometimes system failures like floods and water scarcity and there are huge costs which some cities cannot afford. Water ‘use’ in a city is a complex process. In the countryside, agriculture employs water to cool plants – up to 1000 kg of it per kg of food harvested – and thereby effectively loses that water. By contrast most city uses degrade water rather than consume it, they dirty it chemically, contaminate it biologically, warm it up or do all three.
