As of: February 12, 2024, 6:02 p.m
By: Elena Siegl
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The construction site in Urspring is gigantic.
You can see the serpentines of the channel section, which not only helps the fish overcome the barrage, but also offers new habitat.
© Hans-Helmut Herold
There should be fish ladders at all barrages by the end of 2027.
The company “Uniper” is currently building three of these passes in the region.
District – Huge construction sites are currently located in several parts of the Lech in the region.
Uniper is currently building fish ladders at both the Dessau and Urspring barrages and Epfach.
“The basis for the measures is the EU Water Framework Directive, which requires the construction of fish ladders at all river barrages by the end of 2027,” explains press spokesman Theodoros Reum Schüssel.
The passes are designed for the leader fish Huchen, an upriver migrating fish that is now threatened with extinction.
The Lech is considered Bavaria's most densely developed river.
The energy company Uniper alone operates 23 power plants on the Lech.
There are a total of 32 barrages over a length of around 250 kilometers.
Usually an insurmountable obstacle for fish and other aquatic creatures.
This is where the directive comes in.
Construction of fish ladders in the region started in 2023
“At the request of the Weilheim Water Management Authority, the construction of the systems in Dessau and Urspring was brought forward,” said Reum Schüssel.
Construction began on the Dessau dam in November 2022.
It started in Urspring in February 2023.
The projects have now taken shape - concrete pillars have been embedded and serpentines have been created.
Both systems are scheduled to go into operation in the summer of this year, as planned.
The one in Dessau in July, the one in Urspring in August.
The facility in Epfach should be ready at the end of the year.
Construction started in summer 2023 (we reported).
Eight more fish ladders are planned in the Landsberg and Weilheim-Schongau districts.
Dessau: Limited space and rocky ground make it difficult to build fish ladders
The construction of the fish ladder in Dessau is particularly complex.
This is due to the limited space and rocky ground, says Reum Schüssel.
The available space is clearly defined by slopes and pastures.
Significant parts of the fish ladder will be built directly next to the access road.
Costs of around 8 million euros are currently expected.
According to Reum Schüssel, costs of around 6.5 million euros are planned for Urspring.
Where Uniper fish ladders are being built (orange) and are planned (red) in the region.
© Bayernatlas/Siegl
Together, both passes are intended to extend the continuity over a section of around 24 kilometers and restore the connection with the Litzauer Loop, a particularly ecologically valuable section of the Lech.
Lower reaches of tributary rivers such as the Illach and Gruberbach should also be accessible again for upward migrating fish.
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Several meters of height difference must be overcome
The systems are all constructed in a similar way: In the concrete entry structure in Dessau there are around 34 individual steps, each twelve centimeters high, to make a height difference of around four meters passable.
In Urspring, a height difference of two meters must be overcome - 19 steps of ten centimeters each are built.
The introduction of around 800 liters of water per second through the pass into the Lech forms the so-called attracting current, which is how the fish find their way into the system in the first place.
This is followed by a section of the channel.
According to Reum Schüssel, the course of the stream will be designed as close to nature as possible - with shallow water zones, pools, gravel nests and dead wood structures.
In addition to continuity, the fish should also find new habitat.
A circumstance that Lechranger Patrizia Majowski is happy about.
There will also be a compensating pond in Dessau, and in Urspring the stream will be divided into individual steps by stone crossbars every five meters apart.
Over a length of 500 meters, a further six meter difference in altitude must be overcome.
In Dessau, a fish ladder is being built right next to the access road in a very small space, which makes the work more difficult.
The connecting channel will expand into a compensation pond measuring around 350 square meters.
© Hans-Helmut Herold
Finally, there is the so-called exit structure made of concrete.
A coarse rake prevents coarser material from washing in.
In the event of flooding, the inflow can be reduced by a slider, says Uniper.
Uniper's renaturation measures are welcomed in the Lechtal habitat, says Lech ranger Patrizia Majowski.
There is good communication with the company.
However, the construction on the Lech poses further challenges that are very complex.
For example, there is no bypass option on the Lech that would specifically guide fish downstream.
The entire German Lech region is struggling with siltation
The so-called load transport no longer works either.
The rubble that the Lech was supposed to transport down the river from the Alps would be stopped by the dams.
In some places it has to be introduced artificially, such as in Augsburg, where the groundwater has sunk due to depressions.
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Furthermore, the entire German Lech is struggling with siltation.
Loose gravel is particularly important, for example for microorganisms or fish larvae, explains Majowski.
Things that we need to continue to tackle together – without assigning blame.
The local newspapers in the Weilheim-Schongau district are represented on Instagram under “merkur_wm_sog”.