From 2017 to 2020, a major project was carried out to restore connectivity to the Biała Tarnowska River, an internationally-important ecological corridor in Poland. Three weirs were completely removed, and twelve more obstacles to fish migration were re-constructed to allow fish passage with a series of innovative solutions designed and engineered to be unique for each location.
The Biała Tarnowska River is located in eastern central Poland and flows northwards from the mountain ranges of the Low Beskids in the Polish Flysch Carpathians for 101.8 km, to meet the Dunajec River in the city of Tarnow. It has a catchment area of 983.3sq km with many tributaries and is part of the Vistula River basin.
It is estimated that there are over 19,000 barriers on rivers in Poland. They were built to protect physical infrastructure such as transportation, communication and power distribution networks, and to provide drinking water or as a vital component of a power plant.
Degradation caused by human activity has been observed in the Biała Valley for many years. The weirs and other constructions built for water regulation have contributed to an impairment of the ecosystem which has disrupted geomorphological and biological continuity as well as the cohesion of plant and animal communities. The aquatic and riverine habitats have been fragmented, preventing migration of fishes and other aquatic organisms. Human activity also influenced physiochemical and biological processes.
In the southern stretches of the river, especially in deforested areas, the upper parts are characterised by permanent deep erosion of the riverbed caused by an increase in transport capacity, while in the lower sections there are sandbanks and gravel islands built up due to a decline in large debris being carried down from the upper reaches after the river was straightened and narrowed. This has negatively affected the occurrence and diversity of plants and animals as well as the ecological status and water quality of the river.
In spite of these extreme modifications, many valuable species of plants and animals can still be found in the Biała Valley and, in terms of at least its riverside habitats, Biała Tarnowska is a typical Carpathian river flowing through forests, including alluvial alder forest, arable land and meadows, and it supports a rare tamarisk Myricaria germanica.