An adjustable weir is a simple weir with one movable valve, which is regularly used in ditches and streams. Pushing up the water has several functions. Such as:
- Store water in wet periods to better withstand dry periods.
- Raise the groundwater level in the area. Sometimes up to 400 meters away from the weir, depending on the type of soil and the elevation.
- Slow down the speed of the water discharge.
- Regulating the amount of water that is drained. The latter is done by the valve that can be further opened or closed at any given moment.
At low water levels, no water will flow through the weir. The exact location of the opening is of the utmost importance. The Markenburg adjustable weir is supplied with a small pedestrian bridge. This is used to operate the valve and is therefore often less than an arm's length from the weir. The bridge can also help a person to get across the ditch or stream. Think of farmers, forest rangers and people from the water board. Due to its basic design, the bridge is not intended for tourists or commuters.
Small weirs such as the adjustable weir are often built with wooden planks/beams that are connected at the top with a crossbeam. The reinforcement is also present along the opening so that all standing beams form one whole and can thus absorb the water pressure. The bridges including the railing are usually made of galvanized steel. The running surface consists of grid plates on a construction of galvanized steel girders. This prevents puddles from forming that cause corrosion or slipperiness.
Landscape elements in the Weir photos are not included.