Geography of Stockholm - Lakes and Watercourses

Lakes and Watercourses

The access to fresh water is excellent in Stockholm today, in contrast to the historically horrible state of things, when lakes and watercourses were used as refuse dumps and latrines, causing epidemic cholera and many other diseases. By the 1860s things changed, as water fetched from Årstaviken, the waters south of Södermalm, was treated in the first water-purifying plant at Skanstull and from there distributed through water mains.

In modern times the city gets its water from Lake Mälaren purified by plants at Norsborg and Lovön, together producing 350,000 m³ per day, which mean Stockholmers are consuming 200 litres per day in average. 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.

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. Decreasing usage of several of these substances have reduced these levels in the upper sediments of the lakes.

The Stockholm area used to contain a lot more lakes and watercourses than it does today, much due to land elevation, but also because of lake reclaims for settlements and health. Historical lakes, such as Fatburssjön on Södermalm and Träsket on Norrmalm, were filthy, stinking, and associated with the high mortality in Stockholm until the late 19th century. Other historical lakes, like Packartorgsviken and its interior part Katthavet, were filled with mud and equally stinky. Other lakes still present today were once much larger – such as Magelungen, Drevviken, Judarn, and Råstasjön – while some bays of today once were proper lakes – Brunnsviken and Hammarby sjö.

Like in many other urban areas, the lakes of Stockholm are directly affected by the city's sewer system and pollution from settlements, traffic, and industry. Sewers often reduces the catchment areas of smaller lakes by redirecting surface water to Lake Mälaren or Lake Saltsjön. While nutritious substances such as phosphorus and nitrogen are mostly derived from agriculture, urban areas produce high amounts of metals and organic compounds. In Stockholm, this mostly applies to central bays – such as Klara sjö, Årstaviken, Ulvsundasjön, Riddarfjärden, and Hammarby Sjö - but also waters surrounded by bungalows and villas – like Långsjön in Älvsjö.