8 Kolobrzeska, Bydgoszcz, Poland
The intersection of the Wełna and Nielba rivers at right angles, often incorrectly referred to as bifurcation, located within the city of Wągrowiec. Additionally, it is not a natural phenomenon. The crossing of Nielba and Wełna was made during drainage works by the Cistercians around 1830. The author of this solution was Adalber Schulemann from Bydgoszcz. Its purpose was to protect the city, then called Wongrowitz, against floods and to maintain the appropriate water level on Wełno to drive the mill. The waters of both rivers mix with each other to a small extent. There are no whirlpools where they cross, so the waters of Nielba and Wełna flow almost straight ahead. It is possible due to different physicochemical properties, such as temperature, oxygenation, pH, the presence of such contaminants as phosphorus or nitrogen compounds. These features enable the waters of one river to flow under the waters of the other. The rivers cross almost at right angles. This phenomenon, although it is not a bifurcation, is worth seeing closely.
