Geography of Stockholm

Water is purified at three plants at Bromma, Henriksdal and Loudden, together filtering some 400,000 m³ sewage per day from pollution, including nitrogen and phosphorus, before discharging it into the Baltic Sea.

[4] Levels of several pollutants in lakes in the central parts of the city, especially on the western side, are far above average, including substances such as cadmium, copper, mercury, and lead.

Historical lakes, such as Fatburssjön on Södermalm and Träsket on Norrmalm, were putrid and associated with a high mortality rate in Stockholm until the late 19th century.

[5] As in other urban areas, the lakes of Stockholm are directly affected by the city's sewer system and pollution from settlements, traffic, and industry.

While nutritious substances such as phosphorus and nitrogen are mostly derived from agriculture, urban areas produce high amounts of metals and organic compounds.

[6] By the mid 17th century, the population of the city had resulted in settlements north and south of Gamla stan, on Norrmalm and Södermalm, and the number of bridges had grown considerably, if not their dimensions or quality.

The situation was solved when a traffic committee in 1930 could present the so-called "clover-leaf solution" of engineer Gösta Lundborg and architect Tage William-Olsson inaugurated in 1935.

[8] Meanwhile, across the Riddarfjärden bay, construction works had started on Västerbron, the large bridge offering a north–south passage west of the historical city centre.

A plan for the care and development of a nature reserve often means the city as well as private landowners are obliged to guarantee the maintenance of the area.

[5] There is one national urban park, Kungliga Nationalstadsparken, and three major nature reserves in Stockholm, Kyrksjölöten, Judarskogen and Grimstaskogen while Hansta is likely to become one soon.