Dam removal and restoration of the Aschach River

Gathering and analysing the necessary technical details to convince relevant stakeholders that the removal of obsolete barriers at the Aschach River is a good choice for the region.

Introduction

River Aschach is a tributary of the Danube with a catchment area of 360 kmĀ². It is located in Upper Austria close to the city Eferding and about one hour away from the regional capitol Linz. The river and its floodplains are part of a Natura 2000 site, which hosts a rich fish diversity. The region is home to several iconic, threatened and protected species, including 14 fish species like cactus roach (Rutilus virgo), Balcan spined loach (Sabanejewia balcanica), the thick shelled river mussel (Unio crassus), kingfisher (Alcedo atthis), white throated dipper (Cinclus cinclus) and mammals such as beaver (Castor fiber), otter (Lutra lutra) and several bat species. 22 fish species native to the wider region are identified as migratory species by IUCN. In the near vicinity of the project area River Aschach flows through a marvelous narrow valley with near natural forests on the hillside, which are strictly protected. In the wider valley-bottom following the canyon, some remnants of mires and wet meadows are located. The outstanding natural areas are frequently visited for recreational purposes.

Given the fact, that Austrian rivers are fragmented with a barrier every 900 meter on average, River Aschach is outstanding, because two relatively long free-flowing sections (12 and 16 kilometers) are separated by four small dams only.

At a glance

LocationHartkirchen, Upper Austria
CountryAustria
RiverAschach
Potential km to be opened16
Key habitatsLowland river with floodplain forests and wet meadows
Focal speciesCactus roach, Balcan spined loach, thick shelled river mussel, kingfisher, white throated dipper and mammals such as beaver, otter and several bat species
Project typeDam removal (pre-demolition)
Project websitewww.wwf.at/alles-im-fluss
Project statusLive

Project context and opportunity

The Danube itself and many larger rivers in Austria are impounded and offer only limited habitats for reophilic fish. In addition many barriers (approx. 30.000) interrupt Austrian rivers. For that reason the restoration of free-flowing stretches, is one of the most important tasks to restore healthy rivers in Austria.

The Aschach River offers very good preconditions to do so. There are only a view obstacles and some of them are abandoned.

In a pre-feasibility study conducted in 2021, WWF investigated the status of the obstacles, the general removal feasibility and consulted stakeholders. They found good preconditions for dam removal: by removing those obstacles, a long stretch of about 30 kilometres could be restored. Endangered species such as Balcan spined loach, river mussel and White throated dipper would benefit from dam removal.

The removal of the four barriers is crucial for restoration of the whole river and is foreseen in the official Riverbasin Management Plan. The plan states that removal is the most efficient means of restoration (compared to e.g. technical fish-passes).

Project aims

The overall goal of the project is to restore the continuum of the lower course of the River Aschach. In the current project phase, the project team will provide the necessary technical details to convince relevant stakeholders that the removal of obsolete barriers at the Aschach River is a good choice for their region.

Partners

WWF Austra