The pioneering project, which is the first time this technology has been used in this manner in the UK, catches, cleans and diverts over 40,000 square meters of rainwater run-off directly into the River Taff, instead of pumping it over eight kilometres through the Vale of Glamorgan for treatment, before being pumped into the sea.

The scheme collects surface water from roofs and roads from twelve residential streets in Grangetown, channelling and filtering it through over 100 rain gardens before draining to the river Taff.

Plants and trees soak up the water in rain gardens, and the water is filtered through the soil and the roots which catch and break down the pollutants.

Specific types of trees and plants which are mostly native to Wales and all UK sourced, have been chosen to fit a number of criteria. They are durable, require little maintenance, are pollutant tolerant and have the ability to adapt to very wet or dry conditions.

Greener Grangetown is a joint venture delivered by Cardiff Council; Dwr Cymru Welsh Water; Natural Resources Wales; Arup; ERH Communications and Civil Engineering Ltd with additional financial support from the Landfill Communities Fund.

Cllr Michael Michael, Cabinet Member for Clean Streets and Recycling, said: "This is an innovative project which deserves this prestigious award.

"It appears that many people don't fully understand what the Greener Grangetown scheme is all about. As well as using pioneering technology to remove rainwater from our sewer systems, the scheme has visually improved the area. 130 new trees have been planted, as well as 1,700 square meters of new green space. In time, as the plants and trees grow and spread, Grangetown will be even greener that it is now.

"Taff Embankment, which is part of the scheme, is also part of the Taff Trail and we are now in the final stages of completing this as a new bicycle priority street which will be over 500 meters long, connecting Cardiff Bay to the city centre. As well as this initiative, improvements have also been made to vehicle, pedestrian and cyclist safety at 14 road junctions which are part of the scheme.

"I would like to thank all the partners involved for delivering this project. I would also like to thank the local residents for their patience while the scheme has been built."

Fergus O'Brien, Welsh Water's wastewater strategy manager said, "Sustainable drainage plays a vital role in Welsh Water's long term approach to protecting our customers and improving the environment in spite of the growing pressures from climate change and urbanisation. It does this by enhancing the inherent resilience of our assets and allowing them to cope with the increasing variability of the demands we make on them. 

"To meet our ambitious plans between now and 2050 we need to work in partnership with stakeholders to share knowledge and invest in areas where our priorities overlap.  Greener Grangetown project is a great example of how we can work with forward thinking councils like Cardiff and we hope this will be the first of many such partnerships."

Martyn Evans, Senior Policy Advisor for Natural Resources Wales, said: 

"We're so pleased to have worked on such an innovative and forward-thinking project like Greener Grangetown.This exciting scheme shows a different approach to managing our natural resources - one that looks at the whole picture rather than focusing on single solutions or individual parts of our environment.

"Not only will this scheme help to create a healthy and resilient local environment, but it will support economic and social prosperity for generations to come.

"We've been on board with this project since the beginning and we're thrilled that the project is being recognised with this fantastic award. It's a brilliant example of how organisations can work together to deliver a positive aim, and we hope this type of scheme can be used in many other areas of Wales."