Needle dam

A needle weir is a special form of a weir and is used like this to create an impoundment to make either through the resulting gap stage, the potential energy can be used to generate ( formerly used to drive mills ) or a certain depth of water for navigation above the weir.

The Nadelwehr is diagonal or transverse to the flow axis and has the river run, in contrast to the solid masonry weir not completely shut off. It consists of a series of wooden planks (needles ) which are held on the bottom of the river by a stop at the military base and above the water line on a catwalk of military Bocks by the water pressure. The flow rate is adjusted by removing or adding individual needles.

An example of a still -occupied Nadelwehr found in Lucerne, where the lake level of Lake Lucerne is regulated with a needle weir. The waters of the Reuss is led thereby above the Mill Bridge in a modern turbine power plant. More needle weirs can be found in the Lower Havel Garz, as well as in the Spree in Neubrückenstraße.

Nadelwehr in Hann. flow

Historical Nadelwehr in the city of Lucerne

Nadelwehr in the Meuse at Revin