Nature-based solutions - Sustainable water management

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Rainwater harvesting

Rainwater harvesting and reuse were widespread in Mediterranean areas (including the South of Italy) until half of the nineteen century. The diffusion of water supply systems led to a loss of rainwater harvesting practices. However, the use of rainwater as a not conventional water resources is nowadays gaining momentum, due to largely accepted benefits: for instance, since rainwater is poor of limestone, its reuse for washing clothes increases the lifespan of washing machines.

pioggiaIRIDRA always considers the possibility to harvest and reuse rainwater in its projects, according to reuses suitable with harvested rainwater quality (e.g. toilet flushing, gardening, or pavement cleaning).


  • potable water saving
  • urban runoff reduction
  • optimal reuse for washing machines

More information

Rainwater is a valuable non conventional water resource, usually exploited external water uses, such as:

  • urban crop irrigation and gardening;
  • washing of service areas, parking, roads;
  • car washing;
  • industrial reuse (cooling water);
  • fire prevention system.

Rainwater harvesting can be also an interesting source of water for internal uses, such as:

  • toilet flushing;
  • washing machines;
  • air conditioning.

A disinfection of rainwater stored in a light-proof tank is not necessary, even if rainwater is used for laundry. Many investigations about water quality, especially with respect to microbiological parameters, and about user satisfaction have been carried out and yielded equal or even better marks for rainwater than for water from the mains as far as the applications listed above are concerned.

A rainwater harvesting system is composed by:

  • The collecting surface: only connect suitable roof surfaces if the system does not include a treatment. Take into consideration possible erosion of hazardous matter from the roof. With an appropriate treatment water from pavements can also be used (see corresponding further elements within brackets).
  • Gutters and downspouts (gullies and rainwater drains).
  • Filter – to suit roof surface area (treatment system, e.g. constructed wetland).
  • Tank – above or below ground.
  • Controls and Pump – Use long life booster systems. Single and Duo pump systems can be installed, with varying pump sizes dependant on project size / flow requirements. Duo pump systems alternate pump start ups and have the additional benefit to enable both pumps to run at times of high water demand.
  • A distribution system – which must be clearly separated from the potable water distribution system. All pipes and outlets must be labelled accordingly.

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Rainwater harvesting system for a single house (source Kessel)


IRIDRA's authors are highlighted in bold.

Conte G., "Nuvole e Sciacquoni", Edizioni Ambiente, ISBN 978-88-89014-76-9. 2008. Free e-book link.