The Alster is a right tributary of the Elbe in Northern Germany. It has its source near Henstedt-Ulzburg, Schleswig-Holstein, flows somewhat southwards through much of the Free and Hanseatic City of Hamburg and joins the Elbe in central Hamburg. In total, the Alster is 56 km (35 mi) long and has an incline from 31 m to 4 m above sea level. Its drainage basin is about 587 km2 (227 sq mi), being regarded to most beautiful and widest scenery of nature in Hamburg.
The Alster Lake is Hamburg’s most important waterscape and landscape feature, which is divided into two parts, Inner Alster (Binnenalster) and Outer Alster (Außenalster). While the Elbe river is a tidal navigation of international significance and prone to flooding, Alster is a non-tidal, slow-flowing and in some places, seemingly untouched idyll of nature, in other places tamed and landscaped urban space. In the city center, the river forms two lakes, both prominent features in Hamburg’s cityscape.
Hamburg was founded at the mouth of the Alster river in the 9th century and used it as a port. The water was used to flood the moats of the fortifications. The Alster has been dammed since 1190, originally to power a watermill. In 1235 a further dam was built for a second mill, which changed the shape of the river to be like a lake. In the 15th and 16th century, an Alster canal was built to connect Hamburg with Lübeck. The canal was about 8 km (5.0 mi) long and built from the Alster to the Beste, a tributary of the Trave river, at Sülfeld. Because of the difficulties in holding water, especially near marsh areas, the 91 km (57 mi) long waterway from Hamburg to Lübeck was navigable from 1529 to 1550 only. Hamburg expanded along the shores of the Alster, and several locks were constructed to make the river navigable. Until the 19th century water transport with barges were used up to the town of Kayhude. The barges—transporting building material, fuel, and foods—were staked or hauled.
Ecological and Economic Value
The Alster is the most favorable spot for the Hamburgers to do water sports, sightseeing, recreation, and park-sauntering in the city centre. It is navigatable some 9 km upstream from the mouth. Alster Touristik GmbH (ATG), a subsidiary of the Hamburger Hochbahn, provides public and touristic transport on a fleet of Alster ferries in the city of Hamburg. Along the entire course within Hamburg, rowing or paddle boats are available for rent. In general, the Alster is assessed to be clean, even though the section below the lock at Rathausschleuse and closer to the port may have the occasional floating debris. Hamburg’s Alster and its lakes and canals are famous for its white swans, cared for out of public funds since the 16th century.
Text source: Wikipedia