Weir system, Lower Saxony

The Wittorf weir was built in 1893 and serves to regulate the water level in the Ilmenau. The historical needle weir consists of a weir bottom and weir cheeks made of brickwork and partly poured concrete. A fish ladder with 4 basins made of brick redstone walls is integrated into the right weir cheek. The weir is closed by about 300 hand-set wooden needles made of pitchpin along 14 needle weir trestles in order to maintain the normal water level in the headwater at + 4.96 mNHN compared to the tailwater at +3.18 mNHN. To open the weir, all needles can be pulled and the needle weir trestles lowered to the bottom. Due to their age, these show strong signs of wear and tear and are replaced by welded constructions of identical design. The construction of the new weir trestles must be based on the existing ones in order to maintain the historic, listed character of the weir.