SUPERVISOR: Wolfram GRAF

PROJECT ASSIGNED TO: Alexander AUHSER 

Worldwide rivers, streams and lakes provide ecosystems services ranging from provisioning and regulatory ones, like water supply, maintenance of water quality and flood protection to cultural ones like recreation and tourism (Aylward et al., 2005). Nevertheless, freshwater ecosystems and their biodiversity are under severe pressure worldwide (WWF, 2020). Climate change, land-use change, agriculture, tourism and hydropower production are drivers of threats like overexploitation, species invasion, habitat degradation, flow modification and water pollution (Dudgeon et al., 2006). These problems are existent in small streams of high alpine ecosystems (Füreder, 2010; EEA, 2016). There, for example the operation of hydropower plants frequently leads to changes of the natural hydrologic regime and environmental parameters, that shape the habitats of aquatic organisms (Gabbud et al., 2019; Consoli et al., 2021).

The alps on the other hand bear a great potential of expanding the renewable energy sector. Storage and pump- storage hydropower plants – the prevalent form of hydropower use in the alps – play an essential role in balancing peaks in energy consumption and thereby in creating net stability and fostering security of supply (Wagner et al., 2015).

To establish a tolerable way of human use of riverine ecosystems, to prevent deterioration and ensure achievement of an acceptable ecological condition (the “good ecological status” or the “good ecological potential”) of all water bodies in the EU, the Water Framework Directive was established in the year 2000. Defining this “good ecological potential” to find a tolerable way of hydropower production both in economic and ecological aspects in high alpine ecosystems is the aim of the project “ÖkoResch” (BMLRT, 2021), a cooperation between hydropower companies, the Austrian ministry of Agriculture, Regions and Tourism (BMLRT) and the University of Natural Resources and Life Sciences (BOKU). Macroinvertebrates, as one Biological Quality Elements of the WFD, are potentially biotic indicators for assessing and categorizing the impacts of hydropower use and the effects of possible mitigation measures in high alpine streams (Graf et al., 2020a). Environmental parameters severely altered by hydropower production like temperature, flow velocity, substrate stability, dynamics (Milner & Petts, 1994; Burgherr & Ward, 2001; Lods-Crozet et al., 2001; Milner et al., 2001) are key factor for habitat conditions and therefore shape benthic communities decisively.

This PhD thesis will aim to develop an assessment system to evaluate the impact of residual flow (as a consequence of hydropower production) on indicators and the effects of mitigation measures (e.g. environmental flow implementation) in high alpine ecosystems by investigating impacted as well as unimpacted sites in different streams across the Austrian alps. The thesis most strongly relates to the research clusters “connectivity” and “vulnerability” of the doctoral school HR21, which aim to understand the complex “exchange processes“ in a river continuum, the “physical, chemical, and biological processes” created by anthropogenic alterations in riverine ecosystems and how to deal with those in the form of evaluation and mitigation strategies. Finding a tolerable way of hydropower production further connects to the research clusters “metabolism” and “governance and planning”, as energy consumption is an essential part of a society’s metabolism and integrating hydropower into the energy market, while simultaneously preventing deterioration and conserving biodiversity of aquatic ecosystems is a great challenge for governments, which needs to be tackled and supported by science- based approaches (Hein et al., 2021).

 

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