Needle weir
A needle weir is a form of a weir and, like this, serves to create a damming in order to either make the potential energy usable through the resulting gradient (previously used to drive mills ) or to generate a certain water depth for shipping above the weir system .
The needle weir runs diagonally or transversely to the river axis and, in contrast to the solid, walled weir, does not have to completely shut off the river. It consists of a series of rods called needles, which are held at the bottom of the river by a stop on the bottom of the weir and above the waterline on a catwalk of the weir ram by the water pressure. The needles can consist of different materials, in the past almost always from round timber, more rarely from squared timber, today from steel or aluminum tubes. The flow rate is regulated by removing or adding individual needles.
An example of a needle weir that is still in use today can be found in Lucerne , where the lake level of Lake Lucerne is regulated with a needle weir. The water from the Reuss is fed into a modern turbine power station above the Spreuer bridge . Further needle weirs can be found in the Lower Havel near Grütz and Garz as well as in the Spree near Neubrück .
- Image examples
Historical needle weir in Lucerne
Closing the needle weir in Lucerne
Needle weir on the Werra in Hann. Münden
Needle weir in the Havel near Grütz
Web links
- Needle weirs in the historical picture archive of the Federal Institute for Hydraulic Engineering