Wagrowiec Bifurcation: A Unique Hydrological Phenomenon

On the outskirts of the Polish town of Wagrowiec, two rivers Welna and Nielba intersect at right angle, and almost impossibly, both rivers roll their waters on independently of each other without mingling. The two rivers run into each other, their waters start a whirlwind motion and then continue to flow out into separate riverbeds. Research has shown that mixing of both river waters in the crossing amounts to only 10%. This has been established by analyzing the water for biological communities that differ slightly in the two rivers. The differences have been found to persist even after the crossing. About 2.4 km down, Nielba eventually flows into Welna near Lęgowskie Lake.
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Wagrowiec is located in the middle of the historic Pałuki region in an area rich in hydrological content. The river Wełna is the most prominent element of this hydrographic network in the vicinity of Wagrowiec. In the 19th century, the town decided to regulate the waters of Welma for irrigation purposes. One of the top priorities was to ensure a quick outflow of surplus water.

In terms of technology, the regulation of a river involved straightening and shortening its course, removing natural and artificial obstacles from its current and changing the place of tributary mouths, should such need arise. This ensured not only protection from flood waters, but also the most efficient usage of fertile meadows situated within the river valley. One of the results of water companies’ engineering was the change of location of the mouth of Nielba into a place, where Wełna is divided into its northern and southern arms. The aim of this endeavor was to create a water junction that allowed steering of the flow of both rivers by means of stone-concrete weir. The change of location of the mouth of Nielba into Wełna, carried out by one of the water companies, created the Wagrowiec’s bifurcation, a phenomenon that’s unique to all of Europe.