The water has a pH value of 7.0 or slightly lower, to be compared with approximately 8.0 for seawater. Together with humic substances this sometimes causes a bit brownish water colour, especially in the inner parts. The salinity varies between freshwater and brackish water with poor salinity. In the outer parts of the archipelago, the salinity reaches around 0.6–0.7 per cent by weight, to be compared with at least 1.5 for beginning to taste salty and around 3.0 or more for proper oceanic water. Sea ice is regularly formed in the inner parts every winter.
The Stockholm archipelago is a joint valley landscape that has been shaped – and is still being shaped – by post-glacial rebound. It was not until the Viking Age that the archipelago began to assume its present-day contours. The islands rise by about three millimeters each year. In 1719 the archipelago had an estimated population of 2,900, consisting mostly of fishermen. Today the archipelago is a popular holiday destination with some 50,000 holiday cottages. The Stockholm Archipelago Foundation, dedicated to the preservation of the nature and culture of the archipelago, owns some 15% of its total area. The inhabitants in the archipelago, from around the mid-1400s to the end of the second world war, were combined farmers and fishermen. Spring and autumn fishing was quite intensive in the outer archipelago from 1450 until the mid-1800s, and many fishermen lived for long periods in the outer islands because of the long distances to their permanent houses in the inner archipelago. The combined farming and fishing culture lasted until around 1950–1955 when the younger generation, born during and directly after the war, started to leave the archipelago and look for jobs in the cities on the mainland. Today most of the small farms on the islands are closed and the fishing industry has almost disappeared.
Culture
Many poets, authors and artists have been influenced and fascinated by the Stockholm archipelago. Among them are August Strindberg, Ture Nerman, Roland Svensson, Ernst Didring and Aleister Crowley. Björn Ulvaeus and Benny Andersson from the group ABBA wrote most of their songs in a cabin located on the archipelago. Boating is an extremely popular activity with the sailing race Ornö runt being the largest in the archipelago. This annual race, organised by the Tyresö Boat Club, has taken place every year since 1973. It is open to anyone with a sailing boat but requires registration. There are different entry classes, with the family class being the least competitive. In the winter skaters make excursions over the ice.
Travel
Visiting the larger islands in the archipelago is easy all year round, but during winter period the routes depend on the ice conditions. Several companies have regular routes. The largest ship owner company is Waxholmsbolaget owned by the Stockholm County government. Taxi boats are also available. In summer the archipelago bristles with private boats filled with people who often take advantage of Allemansrätt, a law which gives anyone the rightto go ashore or anchor on any ground not in the direct vicinity of buildings.
