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After heavy rainfall: Sylvensteinsee level increased by several meters

2021-07-19T22:34:07.876Z


Although the Isar lived up to its name “Die ripping” on Monday, the water levels in the past few days were not threatening. The Sylvenstein reservoir made sure of that.


Although the Isar lived up to its name “Die ripping” on Monday, the water levels in the past few days were not threatening.

The Sylvenstein reservoir made sure of that.

Lenggries - Adjusting to the weather situation was not easy for Tobias Lang, responsible for the dam at the Weilheim water management office.

"The forecasts were constantly changing," says Lang when asked.

Initially, it was expected that the rain on Sunday night would bring an influx of around 480 cubic meters per second to the reservoir; the day before the event, the weather service assumed only 70 cubic meters.

“In fact, the peak was 544 cubic meters per second.

That's not quite in the range of a ten-year flood, ”says Lang.

A relatively narrow rain band over the Karwendel was responsible for this.

The precipitation was therefore mainly concentrated in the area of ​​the Upper Isar.

Floods in Bavaria: As a precaution, more space was created in the reservoir

Forecasts or not: As a precaution, Lang had already started on Saturday to create a little more space in the reservoir.

Its water level is usually 750 meters above sea level in summer.

As a result of a slightly increased water supply to the Isar, the level sank by half a meter.

It then went up steadily until Monday night.

The highest level was reached exactly at midnight at 756.56 meters.

"That is 60 percent of the controllable flood retention," says Lang.

So there was still room for improvement.

For comparison: the lake was really full to the brim at the beginning of June 2013 with a value of 762.95 meters.

"The flood relief starts at 763 meters," says Lang.

Sylvensteinsee (Bavaria): Usually 25 cubic meters per second in the direction of the Isar, now it's 200

In the meantime, however, the lake level is falling again. Instead, more water flows into the Isar. If around 25 cubic meters per second are normally emitted, it is now 200. That is not critical - also because, unlike in the Karwendel, there was not that much precipitation in the Isarwinkel. Therefore, the tributaries such as the Arzbach or the Große Gaißach do not bring much more water than usual. At its peak, almost 270 cubic meters per second flowed through Bad Tölz. For comparison: During the August flood in 2005 there were 650. Another number is also interesting: If the Sylvenstein reservoir with its retention volume didn't exist, it would have been 710 cubic meters on Sunday. In Munich, even 830 cubic meters per second would have reached its peak. In fact, due to the memory, there were now only 373.

The reservoir must not become too empty either

It is not yet entirely clear how long the water supply to the Isar will remain so high.

The goal is of course to reach the summer water level again, says Lang.

But so that the lake level does not fall too far, it must also take into account the inflow.

This is currently a little higher than usual because Uniper does not divert water towards the power plants.

"As soon as that starts up again, 40 cubic meters will break away," says Lang.

And after all, the storage tank shouldn't become too empty, as it is responsible for ensuring that there is always enough water in the Isar during dry periods, for example to keep power plants and waste incineration plants running.

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The municipal utilities like to use floods for stowage.

This means that the locks are opened, the Tölzer reservoir becomes a river again and removes debris.

© Angela von Drachenfels

The water delivery at the dam must also be coordinated with the Tölzer Stadtwerke.

They like to use such floods for stowage.

This means that the locks at the Tölzer Reservoir are opened, the lake becomes a river again - and removes some of the gravel.

“Ultimately, we have to coordinate so that there is still enough water to fill the reservoir again,” says Lang.

On the Loisach, too, everything is in balance - even if it looks different on paper

And what about Loisach?

It reached reporting level 1 in Kochel on Sunday.

“At this point, Uniper has to stop producing electricity in the Walchensee power plant.

They adhered to that exactly, ”says Lang.

That means, from this moment on, no more water flows from the Walchensee into the Kochelsee.

The levels on the Loisach rose only slightly on Monday.

The situation in Schlehdorf looked a bit threatening - but only on the screen or on paper.

There the level was just below reporting level four.

"But only because the reporting levels have not yet been adapted to the actual circumstances," says Lang.

The flood protection has been improved there.

So more water can pass through without endangering buildings.

Blocked road free again

There is good news in terms of road closures: B11 and Töl 24 are passable again - at least to a limited extent. The B 11 between Urfeld and Walchensee had to be closed after a mudslide south of Urfeld. The rubble has now been removed from the street, the roadway is clear again according to the Weilheim State Building Authority. At Kreisstraße 24 south of Vorderriss, the demolition wall leading to the Rißbach was temporarily secured with armor stones. The traffic is now diverted on one side on the side facing away from the danger zone. The toll road between Wallgau and Vorderriß will also be open again from Tuesday at 7 a.m. - but only during the day until around 8 p.m. According to Rudolf Plochmann, head of the Tölzer forestry operation, it remains closed at night. In one area it is only accessible on one side.A traffic light regulates the traffic.

By the way: Everything from the region is now also available in our new, regular Bad Tölz newsletter.

Source: merkur

All news articles on 2021-07-19

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