Water reuse through nature-based solutions
The CSO-CW of Gorla Maggiore is located within Gorla Maggiore "Water Park". It has been developed and monitored as a case study of the European funded project OpenNESS.
This green infrastructure is composed of a set of constructed wetlands (CWs), on the shore of the Olona River in an area previously used for poplar plantation. The surface interested by the sewer, which serves 2017 person equivalents, is 20ha and the first flush volume has been estimated at 987 m3.
The site includes a pollutant removal area with a grid, a sedimentation tank and four vertical sub-surface flow CWs, a surface flow CW with multiple roles (pollution retention, buffer for flood events, maintenance of biodiversity and recreation) and a recreational park with restored riparian vegetation, green open space, information panels, walking and cycling paths and other services.

Resources needed

Project cost: € 500,000 – 2,000,000
The Gorla water park has been developed under the sponsorship of the Lombardy Regional Authority, co-funded by Fondazione Cariplo and designed by the engineering firm IRIDRA.

Evidence of success

The main advantages of CW of Gorla Maggiore are:
• in situ treatment of CSO with interception of high pollutant loads, contributing to water quality improvement
• flood mitigation and peak flow reduction
• CAPEX costs comparable with other technologies but with additional ecosystem services improvement; low OPEX and simple management
• landscaping; park area restoration; support to biodiversity, improvement of river habitats,
• social benefits linked to the new park

Potential for learning or transfer

The green infrastructure composed by the CWs and the park performs equal to or even better than the grey alternative for water purification and flood protection. Public authorities can provide direction for implementing these interventions including possibilities for their upscaling and tranferability.
Nature-based solutions such as constructed wetlands contribute to broader and multiple policy goals; they target the efficiency in water regulation but they can also create additional benefits through the improvement of different ecosystem services such as flood mitigation, biodiversity increase or fruition, specially valued by the local residents and stakeholders.

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Main institution
Lombardia, Italy (Italia)
Start Date
January 2012
End Date


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