Crossroads of rivers and Velna Nelba Bashny.Net

Confluence of the rivers - not a rare phenomenon. But you ever seen a river crossroads?
Two rivers and Nelba Velna occurring near the Polish town of Wągrowiec, intersect at right angles to each other, and, river water do not mix. Repeated experiments have shown that if the river water paint in different colors at the intersection of each color in a flow channel. For example, in Velnu poured red paint, and Nelbu blue - at the intersection of the ink is not mixed, blue flowing over red. The secret is the temperature difference between the water and the different rates of flow. Velny water flow down, and Nelby - at the top. Such is the two-level interchange.