Sustainable drainage in streets and parks and large-scale reuse of household water and rainwater are making inroads in cities pioneering responsible water management.
Water is a precious commodity in our geographical context, and it will likely become even more scarce in the coming decades due to climate change. Even countries and regions in which water has historically abounded are expected to see their cycle of regular rains disrupted, with increasingly drier conditions. The international community, therefore, has sounded the alarm on the need to rethink the existing water management model and consumption patterns. Cities around the world have embraced the need for efficiently managing this precious resource.
Pioneering strategies are being implemented in various countries across the world to mitigate the effects of global change. Initiatives that, on their face, appear logical, and even obvious, have not been developed on a large scale until recently. These initiatives range from recycling bathwater (the so-called “grey water”) as flush water to storing and reusing rainwater for irrigation or other uses. A variety of actions could help cities consume less water more sustainably if they were broadly implemented.
The city, an impermeable surface that should cease to be so
Over the centuries, cities have replaced the natural land cover, which gradually percolated rainwater into underground aquifers, with pavements made of non-porous materials such as cement tiles, cobblestones and tarmac. Many urban centres have become large expanses with an almost impermeable surface that does not allow infiltration.
Thus, the rain that falls in cities runs on the surface over large distances, contaminated by particulate pollutants, until it is channelled into gutters. This dirty water is mixed with other wastewater, which must then be treated at wastewater treatment plants using expensive and inefficient processes.
The depletion of the natural moisture in the subsoil, which disrupts the water cycle, is another deleterious effect of urban surfaces that are entirely impermeable.