Operation of Complex Hydropower Schemes and its Impact on the Flow Regime in the Downstream River System under Changing Scenarios

Hydropower is the world’s most important renewable electricity source. More than 40% of European hydroelectric energy is produced in Alpine countries. High-head storage hydropower plants (HPP) contribute significantly to peak energy production as well as electricity grid regulation. Future plant management is faced with several challenges concerning modified availability of water resources due to climate change as well as new economic constraints associated with legal, political and electricity market issues. HPP operation results in unsteady water release to the downstream river system. Hydropeaking is the primary factor of flow regime alteration, impacting the river ecosystem. Even when the biological response to hydropeaking is not fully understood, the recently adapted law on water protection prescribes its mitigation in Switzerland. In this research project, a novel integrative approach to model and assess the impact of the operation of a complex hydropower scheme on the downstream river system is developed. It contains (1) a precipitation-runoff model extended for long-term simulations of glacierized Alpine catchment areas, (2) an operation tool for high-head storage HPP, (3) flow regime generation with cost estimation of hydropeaking mitigation measures and (4) a habitat model of reference river morphologies for a target species. The upper Aare River (Hasliaare) in Switzerland is an Alpine stream, affected by hydropeaking from a complex hydropower scheme with several storage volumes and power houses. Since the 1930s, seasonal water transfer from summer to winter and the amplitude and frequency of daily peak discharge have been continuously increased. Furthermore, the dynamic braided river network with various mesohabitats gave way to a mainly monotonous channel. Although diversity of species and biomass of aquatic biota have drastically decreased, the potential of redevelopment remains. Investigations to improve the river morphology and the flow regime are under discussion. The upper Aare River catchment is therefore an appropriate case study for analysis of the interactions between climatic, hydrological, hydraulic, economic as well as ecological parameters. The simulation of runoff in Alpine catchment areas is essential for optimal hydropower exploitation under normal flow conditions, but also for the analysis of flood events. The semi-distributed conceptual modeling approach Routing System contains a reservoir-based precipitation-runoff transformation model (GSM-SOCONT), extended by dynamic glacier simulation tool. Spatial precipitation and temperature distributions are taken into account for simulating the relevant hydrological processes, such as glacier melt, snowpack constitution and melt, soil infiltration and runoff. The model development, calibration and validation are illustrated for the 2005 flood event, where the flood reduction capacity of the HPP is discussed, as well as future long-term runoff estimations. Climate change scenarios, based on a reference climate period, take into account intra-annual temperature and precipitation variations as well as their long-term tendencies. Runoff series of daily resolution are produced by hourly updating of the meteorological, glaciological and hydrological parameters. An almost complete deglacierization of the upper Aare River basin is simulated for the late 21st century. The resulting reduction of glacier melt in summer and earlier snowmelt in spring change the runoff regime from glacio-nival to nival. The implemented heuristic hydropower modeling tool in Routing System allows simulation of the operating mode of complex HPP. Within the case study of the upper Aare River catchment and despite the complexity of the HPP network, the influence of climate change, electricity market issues, plant enhancements as well as hydropeaking constraints is simulated and assessed. Despite the reduction of future runoff, increased flexibility due to new turbine and pumped-storage capacities allows compensation, especially in the case of volatile electricity prices, and could even partially restore the natural flow regime. Several operational and construction measures to reduce hydropeaking are implemented in the model. Resulting flow regimes as well as the related costs are defined. Operational constraints, such as limitation of turbine discharge, increase of residual flow or limited drawdown range, generate relatively high costs compared to their environmental effectiveness. Better ecological and economic response is achieved by construction measures, such as flow deviation systems or compensation basins installed downstream of the power house outflow where the water is temporarily stored and then released to the river by a guided system. The simulated flow regimes are rated by a river specific habitat model for representative morphologies and three life stages of the target species brown trout (Salmo trutta fario). This is based on results from a 2D hydrodynamic model and in situ investigations undertaken in the framework of a joint project of EAWAG. Steady and dynamic indicators quantify fish habitat suitability and allow comparison through economic indices of the implemented mitigation measures. For the Hasliaare River, investments for mitigation of hydropeaking are only justified by morphological improvements. The developed approach is useful for the enhancement of complex storage hydropower schemes regarding mitigation of altered flow regimes. Despite several uncertainties, it allows operators, authorities and researchers to define and rate the impact of HPP operation on the river network, to ecologically and economically assess mitigation measures and thus to address hydropeaking in a straightforward manner

Beurteilung von Massnahmen zur Reduktion von Schwall und Sunk

Das revidierte Gewässerschutzgesetz schreibt für Schwall-und Sunk-beeingträchtigte Gewässer eine Sanierung des Abflussregimes vor. Um Massnahmen in komplexen Kraftwerkssystemen wirtschaftlich und ökologisch zu beurteilen, ist ein interdisziplinärer Ansatz sinnvoll. Der Betrieb des Kraftwerks wird mit dem Softwaretool Routing System simuliert. Daraus resultiert die Ganglinie im Fluss sowie die durch die zu testende Sanierungsmassnahme entstandenen Kosten. Die Beurteilung der Bachforellenhabitate berücksichtigt nebst den kritischen Entwichlungsstadien der Forelle auch den Einfluss der Gerinnmorphologie

Herausforderungen des heutigen wasserbaulichen Versuchswesens mit drei Beispielen

Die meisten technischen Universitäten oder Hochschulen, welche Bauingenieure ausbilden, verfügen seit annähernd 100 Jahren über wasserbauliche Laboratorien. Darin werden mittels physikalischer Modellierung Elemente von Talsperren, Wasserkraftwerken oder Hochwasserschutz-Maßnahmen überprüft und optimiert. Mehrmals wurde dieser klassischen Methode bereits das Ende vorausgesagt, trotzdem sind die Versuchsanstalten ausgebucht. Die Autorenumreißen den Wandel der Branche und geben drei Beispiele dazu

Flow and waves in a common tailrace channel of two pump-storage plants - physical and numerical simulation

Pump and turbine operations lead to head losses in the tailrace channel. Pumping discharge may be limited due to potential air entrainment into the pump shaft when the downstream reservoir is at its lowest level and the head losses are high. Regarding turbine operations, the limit is given by the maximum level in the Pelton turbine chamber due to high water level in the downstream reservoir and head losses. For the extended Hongrin-Léman pumped-storage scheme in Switzerland, the rapid operations of turbines and pumps lead to highly unsteady flow in the tailrace channel system of the two connected hydropower plants. Negative and positive surges may lead to similar consequences as for stationary operations such as sudden air entrainment into the pump shaft and submerging of the Pelton runner under operation. Therefore flow and head losses tests were performed on a physical model at 1:30 scale together with numerical simulations using the FLOW-3D software. On site measurement of the existing power plant allowed validation of the results. Representative and extreme operational scenarios have been simulated; the main results are discussed and presented

Prévision des crues sur le Yangtsé – Application du concept MINERVE

La gestion des eaux sur le bassin versant du fleuve Yangtsé, dont la surface représente plus de 40 fois celle de la Suisse, est indispensable pour la protection contre les crues mais aussi pour assurer les besoins d’approvisionnement de ses 300 millions d’habitants et des cultures agricoles. Dans le cadre de la coopération Sino-Suisse, l’application du concept MINERVE de prévision hydrologique et de gestion préventive des crues a été initiée en mai 2010. Les développements réalisés concernent le sous-bassin test de la rivière Han, principal affluent du Yangtsé. Après un atelier de transfert de connaissances organisé à l’Ecole Polytechnique Fédérale de Lausanne (EPFL), un modèle de simulation hydrologique a été construit et validé à l’aide du logiciel RS 3.0. Cette application est actuellement greffée sur la base de données de la Changjiang Water Resources Commission (CWRC) et fournit des prévisions hydrologiques à pas de temps horaire en fonctionnement automatique. L’utilisation du modèle et de ses résultats ouvre des perspectives immédiates pour l’évaluation des changements climatiques, l’aide à la décision en situation de crue et son intégration au plan de gestion du risque (RiskPlan) du bassin versant. Les développements réalisés sur la rivière Han pourront alors être progressivement étendus à l’ensemble du bassin versant du Yangtsé

Effects of age and eccentricity on visual target detection

The aim of this study was to examine the effects of aging and target eccentricity on a visual search task comprising 30 images of everyday life projected into a hemisphere, realizing a ±90° visual field. The task performed binocularly allowed participants to freely move their eyes to scan images for an appearing target or distractor stimulus (presented at 10°; 30°, and 50° eccentricity). The distractor stimulus required no response, while the target stimulus required acknowledgment by pressing the response button. One hundred and seventeen healthy subjects (mean age = 49.63 years, SD = 17.40 years, age range 20–78 years) were studied. The results show that target detection performance decreases with age as well as with increasing eccentricity, especially for older subjects. Reaction time also increases with age and eccentricity, but in contrast to target detection, there is no interaction between age and eccentricity. Eye movement analysis showed that younger subjects exhibited a passive search strategy while older subjects exhibited an active search strategy probably as a compensation for their reduced peripheral detection performance

Zum Zusammenhang von Geschlechterungleichheiten in Bildung, Beruf und Karriere : ein Ausblick

Ziel der folgenden Ausführungen im abschliessenden Teil dieses Sammelbands zur Entwicklung und Genese von geschlechtsspezifischen Bildungsungleichheiten ist es, den Blick zu öffnen in Richtung Berufsleben. Wie sind die verbesserten Bildungsmöglichkeiten von Frauen zu interpretieren? Ist es in den letzten Jahrzehnten gelungen, eines der grundlegendsten gesellschaftlichen Ungleichheitsverhältnisse zu beseitigen? Oder beginnt sich dieses sogar zu verkehren in eine gesellschaftliche Benachteiligung der Männer? Wir gehen bei unseren Überlegungen von der These aus, dass ein Abbau von Benachteiligungen der Frauen im Bildungssystem für sich genommen noch wenig aussagekräftig ist, wenn wir uns mit der klassischen soziologischen Frage der Persistenz bzw. des Wandels von gesellschaftlichen Ungleichheiten befassen wollen. Erst wenn die ganze Verknüpfung von Bildung und gesellschaftlicher Ungleichheit in den Blick genommen wird und sich dabei zeigt, dass Frauen ihre Bildungsgewinne auch in entsprechende Chancen im Beschäftigungssystem umsetzen können, sind ihre verbesserten Bildungschancen ein Gewinn für die Individuen und ein Fortschritt für die Gesellschaft – und erst dann könnten mögliche Bildungsvorteile von Frauen, wie sie in den vorliegenden Aufsätzen z.T. diagnostiziert werden, gar als neue gesellschaftliche Benachteiligungen von Männern skandalisiert werden

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Analysis of flood-reduction capacity of hydropower schemes in an Alpine catchment area by semidistributed conceptual modeling

The simulation of run-off in Alpine catchment areas is essential for the optimal operation of high head storage hydropower plants (HPPs) under normal flow conditions, but also in case of flood events. A conceptual semidistributed numerical approach is presented, combining hydrologic modelling and operation of hydraulic works. Spatial rainfall and temperature distributions were taken into account for simulating the dominant hydrologic processes, such as glacier melt, snowpack constitution and melt, soil infiltration and run-off. The object-oriented modelling tool allowed run-off generation, simulation of the operating mode of complex HPP and its impact on the downstream river network for different scenarios. The paper briefly presents the hydrologic model and then the application for the upper Aare catchment in Switzerland, where about half of the area is operated by the Oberhasli hydropower scheme. The development, calibration and validation of the hydrologic model are discussed. Finally, the retention effect of the existing reservoirs and their management, including preventive turbine operations, on flood routing in the Aare River upstream of Lake Brienz is presented for the 2005 historical flood event

Development of a novel driving behavior adaptations questionnaire

ABSTRACT Background: Driving a car requires adapting one's behavior to current task demands taking into account one's capacities. With increasing age, driving-relevant cognitive performance may decrease, creating a need for risk-reducing behavioral adaptations. Three different kinds of behavioral adaptations are known: selection, optimization, and compensation. These can occur on the tactical and the strategic level. Risk-reducing behavioral adaptations should be considered when evaluating older drivers' traffic-related risks. Methods: A questionnaire to assess driving-related behavioral adaptations in older drivers was created. The questionnaire was administered to 61 years older (age 65-87 years; mean age = 70.2 years; SD = 5.5 years; 30 female, 31 male) and 31 younger participants (age 22-55 years; mean age = 30.5 years; SD = 6.3 years; 16 female and 15 male) to explore age and gender differences in behavioral adaptations. Results: Two factors were extracted from the questionnaire, a risk-increasing factor and a risk-reducing factor. Group comparisons revealed significantly more risk-reducing behaviors in older participants (t(84.5) = 2.21, p = 0.013) and females (t(90) = 2.52, p = 0.014) compared, respectively, to younger participants and males. No differences for the risk-increasing factor were found (p > 0.05). Conclusions: The questionnaire seems to be a useful tool to assess driving-related behavioral adaptations aimed at decreasing the risk while driving. The possibility to assess driving-related behavioral adaptations in a systematic way enables a more resource-oriented approach in the evaluation of fitness to drive in older drivers