Optimierung von Mehrzweckspeichern im Hinblick auf Hochwasserrisiko und Ökologie

Modellbasierte Managementsysteme für Flussgebiete mit Mehrzweckspeichern sind heutzutage unverzichtbar für eine optimale Bewirtschaftung. Es wird ein Managementsystem vorgestellt, das mit Hilfe evolutionärer Algorithmen sowohl für den Normalbetrieb als auch für den ereignisbezogenen Betrieb eines Mehrzweckspeichers mehrere Bewirtschaftungsziele gleichzeitig berücksichtigt. Das Ergebnis ist eine Menge von so genannten Pareto-optimalen Lösungen, die die effektivsten Kompromisse darstellen und als transparente Grundlage für Entscheidungsträger dienen können. Zielkonflikte und -synergien können erkannt und analysiert werden. Um die natürliche Abflussdynamik im Normalbetrieb zu berücksichtigen und somit die negativen ökologischen Auswirkungen im Unterlauf eines Mehrzweckspeichers zu minimieren, wird ein dynamisches Betriebsregelkonzept verwendet. Das hier vorgestellte Managementsystem eignet sich ebenfalls zum Einsatz einer adaptiven Steuerung, die auf einer Nachführung aktualisierter Vorhersagen basiert

Re-Operation of Multi-Purpose Reservoirs for Economic and Environmental Benefits

Natural river habitats are subject to continuous changes. The flow regime of a stream affects flow velocity, water depth, sediment transport, water quality and river morphology, as well as the frequency and depth with which floodplains are inundated. The flow regime thus acts as a 'master variable' that influences many aspects of the river habitat. Many aquatic organisms are specialized on being able to cope with the continuously changing environment they inhabit, some are capable of using these circumstances to their advantage and others even depend on them. Reservoir releases that do not imitate the natural flow regime result in changed habitat conditions for organisms inhabiting the affected reaches below the reservoir. In many cases, this leads to an ecological impoverishment of the affected reaches and/or to the invasion of foreign species that are better suited to survive in the changed conditions, in both cases resulting in a changed ecosystem. In order to preserve or restore a natural river habitat, the flow regime of a river that is affected by a reservoir has to imitate the natural flow regime as closely as possible. This concerns properties such as quantity, frequency, duration, timing as well as the rate of change of flow. This paper is a result of an ongoing research project focusing on the reduction of flood risk along rivers regarding both the failure probability of affected structures as well as the damage inflicted upon socio-economic values downstream of reservoirs. At the same time, reservoir releases are modified such that dam-induced hydrologic alteration down-stream is reduced, thus improving downstream habitat conditions. This is achieved by developing tools that allow for improved, model-based reservoir regulation with dynamic releases, producing both economic as well as environmental benefits. A reservoir operation model is used to define dynamic releases which are then optimized with regard to multiple, partly conflicting, objectives (flood protection, dam safety, hydropower production, water supply, hydrologic alteration) using evolutionary algorithms. The methodology is applied to case studies of existing multi-purpose reservoirs in Ger-many and improves existing reservoir operating rules regarding both economic as well as environmental aspects. Compared to conventional operating rules, the dynamic operating rule keeps the reservoir storage levels at a more constant level and produces a more variable reservoir release pattern that follows the natural flow regime. As a result, hydrologic alteration can be reduced significantly, while the storage levels better adhere to the reservoir's flood guide

Can we improve dam safety and ecological dam performance at the same time?

Natural river habitats are subject to continuous changes. The flow regime of a stream affects flow velocity, water depth, sediment transport, water quality and river morphology, as well as the frequency and depth with which floodplains are inundated. The flow regime thus acts as a 'master variable' that influences many aspects of the river habitat. Many aquatic organisms are specialised on being able to cope with the continuously changing environment they inhabit, some are capable of using these circumstances to their advantage and others even depend on them. Reservoir releases that do not imitate the natural flow regime result in changed habitat conditions for organisms inhabiting the affected reaches below the reservoir. In many cases, this leads to an ecological impoverishment of the affected reaches and/or to the invasion of foreign species that are better suited to survive in the changed conditions, in both cases resulting in a changed ecosystem. This research project focuses on the reduction of flood risk along rivers regarding both the failure probability of affected structures as well as the damage inflicted upon socio-economic and ecological values downstream of reservoirs. This is achieved by developing tools that allow for improved, model-based reservoir regulation with dynamic releases. In order to preserve or restore a natural river habitat, the flow regime of a river that is affected by a reservoir has to imitate the natural flow regime as closely as possible. This concerns properties such as quantity, frequency, duration, timing as well as the rate of change of flow. A reservoir operation model is used to define dynamic releases which can then be optimised with regard to multiple target criteria (flood protection, ecological issues) using evolutionary algorithms. The methodology is applied to different study areas in Germany in order to improve existing reservoir operating rules regarding both flood protection as well as ecological aspects

Molecular and morphological characterisation of larvae of the genus Diamesa Meigen, 1835 (Diptera: Chironomidae) in Alpine streams (Ötztal Alps, Austria).

Diamesa species (Diptera, Chironomidae) are widely distributed in freshwater ecosystems, and their life cycles are closely linked to environmental variables such as temperature, water quality, and sediment composition. Their sensitivity to environmental changes, particularly in response to pollution and habitat alterations, makes them valuable indicators of ecosystem health. The challenges associated with the morphological identification of larvae invoke the use of DNA barcoding for species determination. The mitochondrial cytochrome oxidase subunit I (COI) gene is regularly used for species identification but faces limitations, such as similar sequences in closely related species. To overcome this, we explored the use of the internal transcribed spacers (ITS) region in addition to COI for Diamesa larvae identification. Therefore, this study employs a combination of molecular markers alongside traditional morphological identification to enhance species discrimination. In total, 129 specimens were analysed, of which 101 were sampled from a glacier-fed stream in Rotmoostal, and the remaining 28 from spring-fed streams in the neighbouring valleys of Königstal and Timmelstal. This study reveals the inadequacy of utilizing single COI or ITS genes for comprehensive species differentiation within the genus Diamesa. However, the combined application of COI and ITS markers significantly enhances species identification resolution, surpassing the limitations faced by traditional taxonomists. Notably, this is evident in cases involving morphologically indistinguishable species, such as Diamesa latitarsis and Diamesa modesta. It highlights the potential of employing a multi-marker approach for more accurate and reliable Diamesa species identification. This method can be a powerful tool for identifying Diamesa species, shedding light on their remarkable adaptations to extreme environments and the impacts of environmental changes on their populations

Sampling sites in the Ötztal Alps.

Sampling on August 22, 2020 (RM3, RM4), August 23, 2020 (RM0, RM1, RM2), and July 20, 2021 (TJ1, KT1, KT2). For sapling site codes see Table 1; Photos: D. Vondrák.</p

Phylogenetic tree showing species delimitation analysis based on the combination of COI marker genes and internal transcribed spacer (ITS) sequences.

The first three letters in each individual’s code represent the sampling site code (see Table 1). The species names after the sample ID refer to the morphological identification, while colour coding for species is based on molecular assignments.</p