The Czarna Hańcza () is a river in north-eastern Poland and north-western Belarus. It is the largest river of the Suwałki Region and a tributary of the Neman. The river flows through Lake Hańcza, the deepest lake in Poland (maximum depth ), and Wigry Lake in Wigry National Park, before entering the Augustów Canal near Rygol. Its total drainage basin covers , of which lies in Poland. The riverbed contains large postglacial boulders, and the upper course has a gradient of 2.3‰, giving it a near-montane character unusual for the North European Plain. The canal was added to the UNESCO World Heritage Tentative List on 30 January 2004.
Ecology
The river passes through Wigry National Park (established 1989; ), which contains 42 lakes, over 1,700 recorded animal species, 202 bird species, and roughly 250 European beavers. The park was designated a Ramsar wetland site in 2002 and joined Natura 2000 in 2004.
Brown trout (Salmo trutta) is the dominant fish species in the river. A 2023 study in Fisheries & Aquatic Life documented the recovery of the fish community after a wastewater treatment plant failure in Suwałki in July 2018 killed approximately of fish. Species abundance returned to near pre-incident levels within ten months, though the composition initially favoured more tolerant species such as white bream and European perch; brown trout populations recovered with the aid of stocking over the following years. Eutrophication from Suwałki's domestic sewage was historically the primary threat to water quality in the Czarna Hańcza and Lake Wigry; construction of a modern treatment plant with phosphorus precipitation has reduced nutrient loading. The route passes through the Augustów Primeval Forest, where wolves, moose, red deer, and beavers inhabit the surrounding woodland, and through the locks of the Augustów Canal. The trail is rated accessible to beginners and families, with rental stations at Wigry, Czerwony Folwark, and Mańkowa Ruda.
See also
- Augustów Canal
- Biała Hańcza