The site well demonstrates the successful accommodation of nature conservation with operational considerations. The Water Treatment Works is next to the Sunnyside Reservoir and the Stain Hill Reservoirs – sites of Metropolitan Importance for Nature Conservation and contains flower-rich grassland and habitats for water birds. The extensive areas of open water, especially the Grand Junction Reservoir in the north-west of the site, are used by large numbers of birds, particularly in winter. Most of the site is still in operational use so marginal vegetation, where it occurs, is generally sparse. However, the grasslands surrounding the filter beds and buildings are among the most herb-rich grasslands in the Borough and contain several scarce London species often associated with chalk grassland.