Storage flush

from Wikipedia, the free encyclopedia

Reservoir flushing describes a method for clearing the reservoir of a run-of- river power plant or storage power plant from deposits such as sediments, which are formed there due to the lack of sediment transport . When the reservoir is flushed, either the weir flaps of a hydropower plant or the bottom outlets are opened. The deposits in the storage space are intended to be flushed out into the underwater of the power plant. The flushing of reservoirs can be ecologically problematic due to the cloudiness, temperature changes and sediment displacement caused.

When flushing reservoirs, primarily only the fine sludge and sands are transported, as these fractions are most likely to be mobilized. The coarse sediment deposited on the other hand more in the reservoir head of the lake, and would be transported only during a flood. These debris fractions, which are important for the stabilization of the bed and the creation of natural structures ( e.g. spawning grounds ), are only removed to a small extent. Most of the ballast and gravel remain in the reservoirs and are missing in the river below. As a result, the river digs further into its river bed below the power plant and can cause the groundwater level to drop .

Reservoir flushing can be associated with shallow water zones in the upper water of the power plant falling dry very quickly . This can be problematic for fish of all species, especially juvenile fish that are only in the current-protected shallow water areas.

During the flushing of the reservoir, the transported sludge in the underwater can cause an increase in the concentration of suspended matter with simultaneous oxygen consumption. Many aquatic organisms are massively damaged as a result, for some this situation can be lethal . In addition, the habitat can be significantly impaired by massive sludge deposits in bays and eddies and the sealing of the vital gravel gap system, which is also responsible for the self-cleaning power of a river.

Storage space flushing is of particular importance in connection with storage chains . The decaying deposits are flushed from the storage space of one power plant into the storage space of the next. The rinsed deposits from power plant to power plant add up just like their negative ecological consequences.

Regular flushing of the reservoir can also have the positive aspect of sediment accumulation in the underwater. Since the dam acts as a sediment trap, there is no sediment in the underwater, which often leads to erosion and deepening of the water. A reservoir flush brings at least part of the bed load back into the underwater.

In principle, it is not possible to completely flush out the sediments in the reservoirs of dams . On the one hand, a trench forms in the emptied storage space, the immediate course of which is cleared of sediments, while the sludge usually remains to the left and right of the trench. In addition, the coarse bed load, in particular, is only displaced during floods, but floods usually cannot be discharged through the bottom outlet.

Today, storage space flushing for the purpose of clearing sediment is hardly permitted in Central Europe.

Individual evidence

  1. ↑ a b c Michael Detering and Holger Schüttrumpf: Landing and lifespan of dams , in: Wasserwirtschaft, Issue 1/2 2014, Springer-Vieweg-Verlag, Wiesbaden, 2014

Web links