ECOHYDRAULICS

ÖEcohydraulics – an interdisciplinary science for improved process understanding and targeted management of river landscapes and their anthropogenic changes or uses.

The applications of ecohydraulics are relevant wherever it is necessary to assess existing and future changes in flowing waters in terms of their impact on aquatic ecosystems. Due to the intersection of habitat characteristics (e.g., flow velocities and water depths) with habitat requirements, various forms arise in the analysis and evaluation of human interventions and changing environmental factors. These evaluations may be necessary due to direct interventions in the course of flood protection projects, through the use of hydropower, or due to indirect changes caused by climate change.

Sustainable Hydropower – Surge and Drawdown

Using numerical methods in ecohydraulics, assessments and optimizations of the impacts of peak electricity generation by storage power plants are carried out. Unsteady hydraulic methods are combined with the ecological requirements of indicator species (fish/macrozoobenthos) to evaluate habitat suitability of surge stretches at base flow (drawdown) and to quantify the changes caused by the surge. Furthermore, area and cross-sectional analyses are applied, which include the quantification of the areas of drying out (from surge to drawdown) and analyses of the morphological effects on drawdown velocities.

Sustainable Hydropower – Dams

New integrative approaches developed at the IWA enable forecasting of how reservoirs will ecologically develop, also considering the aspect of progressive sediment deposition. The background of this sediment dynamic approach in ecohydraulics is that rivers strive for an equilibrium state through sediment transport and deposition. This approach has been integrated into numerical methods for the assessment of dam stretches in order to be able to carry out evaluations and planning of measures for optimization, depending on the bioregions and the transported sediments.

Sustainable Hydropower – Residual Water

A traditional application area of ecohydraulics, which, through the possibilities of quantification in the discharge/habitat relationship, enables the optimization of residual water releases to meet the seasonal requirements of indicator organisms. The methods for this are usually numerical and, except for questions of passability, are carried out with multidimensional flow approaches.

Sustainable Hydropower – Fish Passages
The detectability of fish passages, both upstream and downstream, and the hydraulic optimization of natural-like migration opportunities for aquatic organisms at existing or new interruptions in river continuity, is a central application area of ecohydraulics. Multidimensional flow models are used here for detailed analyses during monitoring or structural optimizations.

Integrated Hydraulic Engineering and Flood Protection

In the context of European and national legislation, it is necessary to consider the objectives of the European Water Framework Directive in addition to the priority aspects of flood safety in hydraulic engineering activities. This means that aquatic ecological aspects and demands must be taken into account in the planning and implementation of flood protection projects. Here, with the appropriate spatial resolution of the water body geometry, the two goals of “protection from water” and “protection of the water” are considered using ecohydraulic approaches. An assessment of the potential aquatic ecological use of the area under consideration across the entire range of flows is the focus here.

Waterway Management

Active sediment management and river engineering measures are required to keep waterways (such as the Danube, Elbe, Rhine) navigable. To assess the impact of these interventions, ecohydraulic methods are applied to minimize the potential effects of these interventions or to optimize the condition for aquatic ecology through targeted integrative approaches in the use of structural elements. Numerical methods in the area of sediment transport and morphological development are also used here, coupled with ecological demands at the level of large groups (guilds).

Assessment of Climate Change Impacts

Similar to applications for assessing residual water in hydropower use, the assessment of the impacts of global warming on river ecology concerns questions of water availability. Here, integrative forecast models regarding precipitation and runoff development can be combined with the numerical approaches of ecohydraulic procedures to quantitatively depict future scenarios of hydrological development. In this context, aspects of water temperature development, including pollutant transport, must also be represented in the modeling.

Sediment Budget and Sediment Management

The application of ecohydraulics in the field of sediment management, which is particularly related to the use of hydropower, is interdisciplinary in multiple respects. Here, in addition to the intersection of flow conditions affecting aquatic organisms, such as fish, the dynamic components of the solid matter budget are also (numerically) evaluated. This refers on the one hand to the dynamics of sediment relocation in the riverbed in terms of habitat stability and habitat renewal. On the other hand, it involves the analysis and assessment of (increased) suspended sediment loads on indicator species in flowing waters.