Cities less vulnerable through better use of urban water

23 November 2009 Delft University of Technology

Cities must reduce their vulnerability in the area of water management. That is one of the most important conclusions of the research of Rutger de Graaf, who obtained his doctoral title - with honor - on Monday 23 November at Delft University of Technology (TU Delft, The Netherlands). The water that is present in urban areas can easily be used to produce energy, as a source of household water and as a location for new construction.

Solar collector

Rutger de Graaf analysed three potential innovations in the area of water management that could help reduce cities’ vulnerability. The first is the use of municipal water reserves as an energy source. This concept is based on the fact that water surfaces are highly suitable as solar collectors.

Heerhugowaard

This concept was developed and assessed for approx. 2,800 dwellings which are to be built in a new district in the northern Dutch town of Heerhugowaard. In the summer months, heat from the surface water will be pumped underground for storage. This warmth can then be pumped back up in the winter to heat homes and other buildings
De Graaf’s results indicate that CO2 emissions can be reduced by 60 percent compared to conventional heating systems. The extra investment can be recouped in ten years, making the system economical.

Cooling

A city that can rely on a system such as this is no longer dependent on energy transport, because the system uses ambient heat rather than natural gas. Furthermore, there is limited cooling of the surface water in the summer, which may slightly temper the expected rise in urban temperatures due to climate change. Surface water cooling also improves water quality.

Self-sufficiency

The second innovation that De Graaf examined in his research is the feasibility of a fully self-sufficient water system (including drinking water) for the same area in Heerhugowaard.
De Graaf established the technical feasibility of extracting drinking water from surface water, but a fully self-sufficient system is unfeasible. Nevertheless, the amount of water that would need to be pumped in from elsewhere would be less than 5% of total annual usage, even in a dry year like 2003. The costs for a system like this would be considerably higher than for a conventional drinking water system.
De Graaf also looked into capturing rainwater as a means toward reducing the demand for municipal drinking water. If all houses had rain water cisterns, the demand for water could be reduced by up to 27 percent. The economic benefit to households would be limited however: 118 euros per year per household.

Floating cities

The third innovative concept is the use of water within the city limits as a site for new construction. Surface water is taking up more and more space in urban area. New municipal districts with a high proportion of surface water face operational challenges.
Floating cities, or ‘building above the water’, is a tenable solution, according to De Graaf. Being an inherently flexible method, floating cities also provide opportunities for responding to the specific wishes of residents. De Graaf is certain that floating cities will be considered just as normal in a hundred years’ time as the automobile is now.

http://www.tudelft.nl/live/pagina.jsp?id=54ef911e-4fce-41b8-8671-89a67dd18898&lang=en