The Glenbrook is a tributary of the Salmons Brook. It flows through underground pipes for much of its length. Hidden away it is damaged, and when it first emerges above ground it is already very badly polluted. Six linked wetlands have been created here to filter pollutants from the stream. The flow is directed through each wetland, being successively cleaned as it is slowed through the basins. Plants use nutrients such as phosphate and nitrate to grow, removing them from the water and stopping them polluting the stream. Bacteria in the soil and root systems break down oils and heavy metals. Once established the planted wetlands not only clean the water, they also add a new dimension to the habitat mosaic for wildlife, and give interest and colour for those passing by.