One of the two towers of Waternet’s new head office in Amsterdam has a catchment for capturing rainwater falling onto the buildings. With the realisation of its own premises, Waternet has set an example of how to solve the rainwater buffering problem in closely-built areas.
As Amsterdam’s water grid manager, Waternet is responsible for supplying drinking water and processing waste water. It intended the water concept for the building situated along the Amstel River, construction on which was completed in 2005, as an example of buffering rainwater and decentralised processing.
An open rainwater buffer was realised below one of the towers, with an area of 1400 m2. The water buffer covers a large part of the 1880 m2 site. It serves two functions: to temporarily store rainwater before it is drained into the Amstel after have undergone purification, and to store greywater for use in the building. It is the intention that the greywater be used in the future for flushing toilets, as cleaning water and in the air conditioning system. The reservoir allows for fluctuations of up to 30 cm in the water level. Multi-level purification reservoirs have been realised along two sides of the reservoir for purifying the water. The plants in the purification reservoir are part of the aesthetically pleasing design. The stepped structure means that the purification works even if the water level changes. The bottom of the reservoir is waterproofed.
The main entrance is reached by crossing a bridge over the water, which serves to enhance the aesthetic value of the water. Dreiseitl et al., 2006