sié

Sió is a river in southern Hungary, located in the Transdanubian region. It is part of the Danube river basin and serves as a tributary to the Danube. The river rises in the Mecsek Mountains and flows generally southeast, draining portions of Baranya and Tolna counties before joining the Danube.

In addition to the natural watercourse, the Sió is closely linked to a major water-management system known as the Sió Canal. Constructed in the 18th and 19th centuries, the canal was designed to drain marshlands, regulate water levels, and support agricultural development in the region. The canal diverts water from the Danube toward Lake Balaton, helping to balance the Balaton’s water level during dry periods and to improve drainage in surrounding low-lying areas. During wetter periods, water management practices in the canal network can influence flows within the Sió basin and toward the Danube.

The Sió basin has ecological and economic significance. Wetlands and associated habitats in the region support birdlife and other wildlife, while the surrounding lands have long supported farming and village communities. The river and canal system have shaped land use, infrastructure, and regional planning, and continue to be a focus of water-management and environmental monitoring efforts.

Sió is primarily known as a river in Hungary and for its association with the Sió Canal, which connects Danube water management with Lake Balaton and regional drainage. See also Lake Balaton, Danube River, Sió Canal.