Surge operation

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Surge operation (also surge operation) describes an operating mode of hydropower plants . Turbines are temporarily suspended or put into operation to increase energy generation . In run-of-river power plants , water is initially dammed up in the duct above. In the upstream section, the water level rises, and in the downstream section, the water level drops due to the reduced discharge. Subsequently, the water level in the upper section is lowered again via the turbine admission. In the lower section, the inflow creates a surge. Due to the increased water level difference, the energy generation is increased compared to normal operation. The surge operation can be carried out for several sections in a row (use of a cascade effect). In storage power plants , the surge operation is a brief increase in the flow.

Surge operation is an artificial intervention in the flow of water in flowing water . Surge operation usually has a flow characteristic that deviates significantly from the natural runoff and can cause ecological problems.

Environmental impact

Fluctuations in water temperature

The entry of stagnant water into a flowing body of water leads to large daily fluctuations in the water temperature of the flowing body of water. Since the activity of fish and other organisms is strongly dependent on the water temperature, a change in the water temperature that occurs several times a day means great stress for these organisms .

Change in river morphology

Daily fluctuations in the water flow, which occur only a few times a year under natural conditions, cause great changes in the river morphology . So z. B. gravel banks flooded several times a day and thereby gradually eroded. The different flow conditions mean different deposits in deeper areas of the flowing water such. B. behind groynes .

Change in water quality

The entry of water, which differs in water quality from that of the flowing water, results in a change in water quality at different times of the day. Furthermore, the water quality of the flowing water is changed by the different flow conditions and water flow. Hydropeaking causes a higher entry of fine sediments and suspended matter , causing such a turbidity of the water because of the increasing suspended solids content. The different proportion of fine sediments is z. B. in direct connection with the development of fish larvae, whereby more fine sediments mean a decrease in fish larvae.

Decrease in the range of habitats

The daily fluctuations in the water flow lead to a loss of habitat . Many animals such as B. juvenile fish and fly larvae lose a large part of their habitats, since flow-safe shallow water zones dry out or are flooded several times a day. Young fish often suffocate in remaining puddles from which they could no longer migrate in time. The effects of the flood operation on the habitat is strongly dependent on the morphology of the flowing water. It may well be possible that there are habitats for fish in both sunk and flood. However, they are often so far apart that they cannot be reached by young fish in the short times when the water flow changes. In this case the fish get stranded or they are caught in the strong current and drift away.

Decrease in biomass

A significant decrease in the biomass in the river can be seen in rivers that are influenced by surge operation . This can be explained by the summation of the influences mentioned above. Fluctuations in water temperature, changes in river morphology, changes in water quality and a decrease in the number of habitats all cause a massive decline in biomass. Declines of 90% of the original biomass have been scientifically documented in some rivers . However, this decline has to be seen in the context of time, since the effects on a river with a hydropower plant do not occur once. Many bodies of water suffer from multiple floods every day. The relationship between flood and sink as well as the water morphology can be emphasized as special factors. The higher the difference between surge and surge, the stronger the effects of the above-mentioned influences on the biomass in a flowing water.

Decrease in population densities

Beaching, drift, fluctuations in water temperature, changes in water quality, changes in river morphology, a decrease in the number of habitats and a decrease in biomass lead to a decrease in the population density of various organisms. The populations are due to the steady loss of z. B. parts of the juvenile age groups, but also thinned out in the long term due to the decrease in food supply . This effect can lead to entire types of organisms disappearing from the running water (see change in biodiversity). Again, the difference between flood and sunk as well as the water morphology show up as serious factors in the influence of flood operation on population density. This results in different strong decreases within the population densities for each affected river.

Change in biodiversity

A significant decrease in biodiversity can be seen in rivers with flood operation . The influences listed above, such as fluctuations in water temperature, changes in river morphology, changes in water quality, but also decreases in biomass and population densities, cause many types of organisms to disappear from the affected river in the long term. Many organisms such as B. the trout , are very sensitive to changes in their habitat . The recurring flood operations mean that many organisms in the affected flowing water are no longer able to survive or that there are no self-sustaining populations. Due to the consequent loss of z. B. juvenile fish of a species, stranded or drifted, the populations are prevented in the long term from forming or maintaining self-sustaining populations. As a special factor, one can again highlight the relationship between surge and sink. The higher the difference between flood and sink, the stronger the effects of flood operation on the biodiversity of a body of water. Due to the unique morphology of each river, the impact on the biodiversity of the affected river is different. In general, however, it can be said that surge operation leads to a decrease in biodiversity.

Danger to life for people

For people in the river bed, sudden sharp increases in water level and flow speed represent a high risk potential. Fishermen standing in shallow water, swimmers bathing in almost standing water, boaters in moderate waves can be so surprised by a rapid change in conditions that they do so No longer reaching the shore safely, but being driven off, with the risk of capsizing, injuring oneself, drowning and dying. Often prohibition signs with writing and drawing of a breaking wave indicate the danger, only rarely is a surge announced by a siren.

Web links

Individual evidence

  1. ↑ http://tirol.orf.at/news/stories/2724093/ Fischer drowns in Gerlosbach, orf.at July 30, 2015, accessed July 30, 2015.