Despite the presence of both natural and artificial waterways, Paris and the inner ring of suburbs have only 2% of surface water, that is therefore visible. However, a wide variety of water can be identified: surface water (river, streams, canals, lakes), purified used water, drainage water, heating and air-conditioning water, rainwater, groundwater, greywater, swimming pool and ice-skating rink water…
The most spectacular type is without a doubt groundwater, particularly that which is just below the surface of the city. Groundwater was for a long time used as a resource for agriculture and industry. The disappearance of these activities means that it often rises to its natural level. The presence of this water interferes with urbanised ground, underground infrastructures (flooding, pumping of drainage water) and polluted or fragile ground (gypsum, clay).
This hidden resource offers an opportunity to rediscover the water in the city, to diversify its uses (watering, amenities, energy…) and to economise on more fragile resources, notably those exploited in the production of drinking water.