Hydromorphological Expert’s Opinion on Reservoir Flushing

We have asked the engineering office UHM River Engineering, Karlsruhe (Germany) for a statement on the effects of reservoir flushings on the Ötztaler Ache river below the planned hydroelectric power plant up to the estuary into the river Inn.

The questions to be answered were:

1. Will the river bed of the Ötztaler Ache change due to the new hydropower plant on the section from the town of Habichen to the confluence with the river Inn?
2. Will a possible change alter the habitat in and around the river?
3. Will there be danger for sportsmen, excursionists and tourists?

We were compelled to do this on the one hand because of the statements of the mayor of Oetz, Falkner, according to which the power plant would not cause any changes on the Wellerbrücke section, or literally:

„Concerning the impact on the whitewater course in the area of the Wellerbrücke, every written syllable is a waste of time. Anyone who has taken only a brief look at the power plant plans knows that the water that is taken in Tumpen will be returned 1:1 to the river bed of the Ötztaler Ache half a kilometre before the Wellerbrücke section. This means that there will be no change in the water level in the area of the Wellerbrücke!“ (transl.) (acc. to „Information der Gemeinde Oetz“ website of municipality of Oetz, 01.04.2020)

… and on the other hand the statement of the Ötztaler Wasserkraft GmbH that says

„The kayaking section is not affected by this project.“ (transl.) (Newspaper Tiroler Tageszeitung, 23.05.2020).

They can claim this however according to the expert statement they cannot know. 


Statement UHM River Engineering

According to the expert statement, there are two main points missing in the project documentation:

Change of the sediment regime

It is unclear how the power plant will affect the sediment regime of the Ötztaler Ache. By taking water from the river to drive the turbines the transport energy of the water is reduced in the diverted section. Therefore, in the long term bedload remains there, which in turn is missing in the section after the reintroduction. Below the reintroduction, the transport capacity is not reduced because all the water is back in the river bed. In the long run, the Ötztaler Ache will be deepened into its bed, because the same amount of sediment can be transported away, but less sediment comes from above.

Surge & Sunk effects

It is also unclear what effect flushing waves have on the river below the hydrop power plant up to the confluence with the river Inn. Downstream of the power plant the Ötztaler Ache has a steep river bed with little variation in width, therefore flushing waves can only pass through to the Inn with little attenuation. An operating plan is therefore needed to prevent excessive water rises. Apart from such an operating plan – which does not seem to exist, as it does not appear in the documents – extraordinary operating conditions can always occur. In such a case (e.g. caused by a machine failure or flotsam) the flaps of the reservoir are opened, so that the content of the reservoir adds up as a wave to the flow in the river bed.

Read the statement yourself – it is only 3 pages! (Although we only have it in German as of of now, we’re sorry)

We demand investigation instead of allegations!

In the meantime we have sent this statement to the office of LHStv Josef Geisler and to the Ötztaler Wasserkraft GmbH with the request to investigate our concerns. From the office of LHStv Geisler we received the reply that the statement had been sent to the water law authority for examination.

We are very sceptical. But let’s wait and see.


Bitte hinterlasse eine Antwort