Alfred Wuest

Alfred Wuest
Eawag: Das Wasserforschungs-Institut des ETH-Bereichs | Eawag · Surf

About

266
Publications
82,588
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10,290
Citations
Citations since 2017
79 Research Items
4684 Citations
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201720182019202020212022202302004006008001,000
201720182019202020212022202302004006008001,000

Publications

Publications (266)
Article
Full-text available
Gravity currents contribute to the transport of heat and mass in atmospheric and aquatic environments. In aquatic systems subject to daily surface cooling, gravity currents propagate through turbulent convective surroundings. Yet, the effects of thermal convection on aquatic gravity currents remain to be quantified. This paper demonstrates how the...
Article
Full-text available
Climate change and reduction in nutrient loads have significant effects on primary production and phytoplankton growth dynamics. Since in the last few decades in many regions, nutrients in lakes were reduced simultaneously as the climate changed. Yet, it remains unclear which of the two has impacted primary production the most. In this study, we co...
Preprint
Climate change and reduction in nutrient loads have significant effects on primary production and phytoplankton growth dynamics. Since in the last few decades in many regions, nutrients in lakes were reduced simultaneously as the climate changed. Yet, it remains unclear which of the two has impacted primary production the most. In this study, we co...
Article
Full-text available
Lake Nyos, a deep crater lake, located in the north-west of Cameroon, was permanently stratified below 50 m depth due to subaquatic sources supplying warm, salty and CO 2 -enriched water into the deepest reaches. The high CO 2 content in these source waters caused the 1986 limnic eruption. The deep inflowing water is denser than the hypolimnetic wa...
Article
Full-text available
Hydroelectric power (HP) represents the main source of electricity in Africa, including the Democratic Republic of Congo. The demand for new dam construction is high, and major projects are currently progressing through planning and implementation stages. New HP dams should comply with both past and emerging environmental requirements. River system...
Preprint
Spatial variability of physical properties induced by circulation and stirring remains unaccounted for in the energy pathway of inland waters. Recent efforts in microstructure turbulence measurements have unraveled the overall energy budget in lakes. Yet, a paucity of lake-wide turbulence measurements hinders our ability to assess how representativ...
Article
Propelled by the rapid development of equipment, technology and computational power, the monitoring and simulation of the hydrodynamics in lakes have steadily advanced. In contrast, water quality simulations are more difficult to implement, due to the difficulty in obtaining large-scale, spatially resolved field observations for model validation an...
Article
Full-text available
When lakes experience surface cooling, the shallow littoral region cools faster than the deep pelagic waters. The lateral density gradient resulting from this differential cooling can trigger a cold downslope density current that intrudes at the base of the mixed layer during stratified conditions. This process is known as a thermal siphon (TS). TS...
Article
Full-text available
Cooling the surface of freshwater bodies, whose temperatures are above the temperature of maximum density, can generate differential cooling between shallow and deep regions. When surface cooling occurs over a long enough period, the thermally induced cross-shore pressure gradient may drive an overturning circulation, a phenomenon called 'thermal s...
Article
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Turbulent mixing controls the vertical transfer of heat, gases and nutrients in stratified water bodies, shaping their response to environmental forcing. Nevertheless, due to technical limitations, the redistribution of wind-derived energy fuelling turbulence within stratified lakes has only been mapped over short (sub-annual) timescales. Here we p...
Article
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Water inherent optical properties (IOPs) contain integrative information on the optical constituents of surface waters. In lakes, IOP measurements have not been traditionally collected. This study describes how high-frequency IOP profiles can be used to document short-term physical and biogeochemical processes that ultimately influence the long-ter...
Chapter
Aim: In this article, we describe the energetics and dynamics of small-scale turbulence and mixing in stratified water bodies. Turbulence in the stratified interior of a water body arises when wind-driven internal motions become unstable and transfer their energy towards smaller-scale motions. The resulting turbulent mixing drives weak but continuo...
Article
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Planktothrix rubescens is a harmful planktonic cyanobacterium, forming concentrated metalimnetic populations in deep oligo- and mesotrophic lakes, even after successful restoration. In Lake Zurich (Switzerland), P. rubescens emerged as a keystone species with annual mass developments since the 1970s. Its success was partly attributed to effects of...
Article
Full-text available
Environmental sciences depend heavily on observational data. Successful studies of ecological processes in lakes require in-situ data that cover the relevant temporal scales from milliseconds to entire seasons. Temporal and spatial coverage requirements represent a non-trivial challenge in lake sciences, which have traditionally used sampling campa...
Preprint
Full-text available
When lakes experience surface cooling, the shallow littoral region cools faster than the deep pelagic waters. The lateral density gradient resulting from this differential cooling can trigger a cold downslope density current that intrudes at the base of the mixed layer during stratified conditions. This process is known as thermal siphon (TS). TS f...
Article
Full-text available
Diese Arbeitsanleitung bietet einen Leitfaden zur Analyse der Sauerstoffzehrung und der NettoÖkosystemproduktion in Seen. Diese beiden Grössen bilden wichtige Grundlagen zur Bestimmung der See-Gesundheit und ermöglichen, deren zeitliche Entwicklung zu untersuchen. Aufbauend auf den beiden in Aqua & Gas erschienenen Artikeln «Sauerstoffzehrung in Se...
Article
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The rates of gross primary production (GPP), ecosystem respiration (R) and net ecosystem production (NEP) provide quantitative information about the cycling of carbon and energy in aquatic ecosystems. In lakes, metabolic rates are often diagnosed from diel oxygen fluctuations recorded with high-resolution sondes. This requires that the imprint of e...
Article
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This study presents a novel concept for estimating net ecosystem production (NEP), the export of organic carbon (OC) from the productive surface layer to the deep‐water (hypolimnion) of 11 seasonally stratified lakes, varying in depth and trophic state. As oxygen remineralizes settling OC at a constant ratio, NEP is equivalent to the areal hypolimn...
Article
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Die Primärproduktion (Algenwachstum) in Seen ist die Basis der see-internen Nahrungskette. Sie hat Einfluss auf die Wasserqualität und den Sauerstoffgehalt im Tiefenwasser und trägt zur Einlagerung von Kohlenstoff in den Sedimenten bei. Eine kürzlich für mehrere Schweizer Seen getestete Methode erlaubt es, die Netto-Ökosystemproduktion mit vergleic...
Article
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Decline in total phosphorus (TP) during lake reoligotrophication does not apparently immediately influence carbon assimilation or deep-water oxygen levels. Traditional monitoring and interpretation do not typically consider the amount of organic carbon exported from the productive zone into the hypolimnion as a measure of net ecosystem production....
Article
Full-text available
Harmful blooms of the filamentous cyanobacteria Planktothrix rubescens have become common in many lakes as they have recovered from eutrophication over the last decades. These cyanobacteria, capable of regulating their vertical position, often flourish at the thermocline to form a deep chlorophyll maximum. In Lake Zurich (Switzerland), they accumul...
Article
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In situ observations of biophysical interactions in natural waters typically focus on physical mechanisms influencing biological activity. Yet, biological activity can also drive physical processes in aquatic environments. A community of photoautotrophic, motile and heavy bacteria—Chromatium okenii, which requires light, sulfide, and anoxic conditi...
Article
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Nutrient loading, in combination with climate change are important drivers of primary productivity in lakes. Understanding and forecasting future changes in primary production (PP) in response to local and global forcing are major challenges for developing sustainable lake management. The objective of this study is to understand and characterize th...
Article
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High-resolution lake and reservoir bathymetric surveys can pinpoint locations that may experience underwater landslides (subaquatic sedimentary mass movements). These can pose a risk to underwater and shoreline infrastructure. This paper outlines an approach for using spatial variation in sedimentary patterns to identify areas susceptible to subaqu...
Article
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This study investigated the consumption of oxygen (O2) in 11 European lakes ranging from 48 m to 372 m deep. In lakes less than ~ 100 m deep, the main pathways for O2 consumption were organic matter (OM) mineralization at the sediment surface and oxidation of reduced compounds diffusing up from the sediment. In deeper lakes, mineralization of OM tr...
Article
Understanding lake dynamics is crucial to provide scientifically credible information for ecosystem management. In this context, three-dimensional hydrodynamic models are a key information source to assess critical but often subtle changes in lake dynamics occurring at all spatio-temporal scales. However, those models require time-consuming calibra...
Conference Paper
Full-text available
Lake managers are facing the problem of a pervasive decline of the ice-covered period and increasing risks associated with traditional winter activities. Better predictions of ice phenology will come from better global characterisations of the under-ice heat dynamics. Although recent in-situ studies have broadened our understanding of under-ice phy...
Conference Paper
Full-text available
Lake managers are facing the problem of decline in the ice-covered period with increasing risks associated with traditional winter activity. There is a need to provide realistic predictions of ice phenology. The physics of ice-covered waters, however, remain only partially characterized. Our goal is to provide a more in-depth understanding of the p...
Article
Periodic winds acting on a stratified waterbody can amplify normal modes of motion and enhance the basin-scale circulation via resonance. Here, we use idealized large-eddy simulations to investigate the flow features and quantify the horizontal transport in periodically wind-forced stratified basins. Motivated by observations in lakes, we focus on...
Article
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Environmental management depends on high-quality monitoring and its meaningful interpretation. The combination of local weather dynamics, regional anthropogenic stresses and global environmental changes make the evaluation of monitoring information in dynamic freshwater systems a challenging task. While the lake ecosystems gather many complex bioge...
Article
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The understanding of physical dynamics is crucial to provide scientifically credible information on lake ecosystem management. We show how the combination of in situ observations, remote sensing data, and three-dimensional hydrodynamic (3D) numerical simulations is capable of resolving various spatiotemporal scales involved in lake dynamics. This c...
Article
To understand water quality degradation during hypoxia, we need to understand sediment oxygen fluxes, the main oxygen sink in shallow hypolimnia. Kinetic models which integrate diffusion and consumption of dissolved oxygen (DO) in sediments usually assume a downward flux of DO from the sediment-water interface (SWI) with a zero-flux condition at th...
Article
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In ice‐covered lakes, penetrative radiation warms fluid beneath a diffusive boundary layer, thereby increasing its density and providing energy for convection in a diurnally‐active, deepening mixed layer. Shallow regions are differentially heated to warmer temperatures, driving turbulent gravity currents that transport warm water downslope and into...
Article
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Areal oxygen (O2) consumption in deeper layers of stratified lakes and reservoirs depends on the amount of settling organic matter. As phosphorus (P) limits primary production in most lakes, protective and remediation efforts often seek to reduce P input. However, lower P concentrations do not always lead to lower O2 consumption rates. This study u...
Article
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In stratified natural waters, convective processes tend to form nearly homogeneous mixed layers. However, shear‐driven turbulence generated by large‐scale background flow often rapidly smooths them through mixing with the stratified surroundings. Here we studied the effect of background turbulence on convectively‐driven mixed layers for the case of...
Article
River engineering projects are developing rapidly across the globe, drastically modifying water courses and sediment transfer. Investigations of the impact of engineering works focuses usually on short‐term impacts, thus a longer‐term perspective is still missing on the effects that such projects have. The ‘Jura Water Corrections’ – the largest riv...
Article
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We derive the mechanical energy budget for shallow, ice‐covered lakes energized by penetrative solar radiation. Radiation increases the available and background components of the potential energy at different rates. Available potential energy drives under‐ice motion, including diurnally‐active turbulence in a near‐surface convective mixing layer (C...
Article
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We report novel results of a numerical experiment designed for examining the basin-scale hydrodynamics that control the mass, momentum, and energy distribution in a daily wind-forced, small thermally-stratified basin. For this purpose, the 3-D Boussinesq equations of motion were numerically solved using large-eddy simulation (LES) in a simplified (...
Poster
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When atmospheric conditions are acceptable, Earth Observations by polar orbiting satellites may at best provide daily information of inland waters optical properties, corresponding to a snapshot of local water quality conditions. However, optical properties can be subject of sub-diel variations, which has implications on one hand for the assessment...
Article
Full-text available
Measures to reduce lake phosphorus concentrations have been encouragingly successful in many parts of the world. After significant eutrophication in the twentieth century, nutrient concentrations have declined in many natural settings. In addition to these direct anthropogenic impacts, however, climate change is also altering various processes in l...
Conference Paper
Full-text available
In-situ observations show that in ice-covered lakes, radiatively-heating drives complex transport mechanisms. Among the identified processes, we observe convective cells, buoyancy-driven flows, and internal waves. Yet, there are only a few observations of basin-scale circulation in such systems. The circulation will depend on the radiative forcing,...
Poster
Full-text available
Measuring primary production (PP) is of major importance to evaluate how lakes are recovering from eutrophication. The classical sampling method involves radiolabelled carbon incubated in bottles at selected depth. Yet the logistic associated with this method prevents scientists from sampling the high frequency dynamics of PP. Alternative methods a...
Poster
Full-text available
In lakes, basin-scale processes such as internal waves and gyres induce lateral variability in almost all aspects of water constituents. Emerging measuring techniques, coupled together with 3D models, have opened the possibility to investigate the lateral variability of physical processes. However, the distribution of small-scale turbulent quantiti...
Article
This special issue of Inland Waters focuses on recent under-ice research in Lake Onego, Russia. Compared to open waters, research on ice-covered lakes is sparse because of the demanding work environment and logistics in the field (Kirillin et al. 2012). In the past, large lakes in particular, such as the European Lakes Onego (61°36′10.52′′N, 35°34′...
Article
Full-text available
Remote sensing helps foster our understanding of inland water processes allowing a synoptic view of water quality parameters. In the context of global monitoring of inland waters, we demonstrate the benefit of combining in-situ water analysis, hydrodynamic modelling and remote sensing for investigating biogeochemical processes. This methodology has...
Article
Full-text available
The understanding of lakes physical dynamics is crucial to provide scientifically credible information for ecosystem management. We show how the combination of in-situ data, remote sensing observations and three-dimensional hydrodynamic numerical simulations is capable of delivering various spatio-temporal scales involved in lakes dynamics. This co...
Article
Full-text available
The assessment of ecological impacts of pumped-storage (PS) hydropower plants on the two connected water bodies is usually based on present climatic conditions. However, significant changes in climate must be expected during their long concession periods. We, therefore, investigate the combined effects of climate change and PS operations on water t...
Article
Full-text available
We investigated radiatively driven under-ice convection in Lake Onego (Russia) during 3 consecutive late winters. In ice-covered lakes, where the temperature of water is below the temperature of maximum density, radiatively driven heating in the upper water column induces unstable density distributions leading to gravitational convection. In this w...
Article
Full-text available
Lake productivity is fundamental to biogeochemical budgets as well as estimating ecological state and predicting future development. Combining modelling with Earth Observation data facilitates a new perspective for studying lake primary production. In this study, primary production was modelled in the large Lake Geneva using the MEdium Resolution I...
Article
Lakes and other confined water bodies are not exposed to tides, and their wind forcing is usually much weaker compared to ocean basins and estuaries. Hence, convective processes are often the dominant drivers for shaping mixing and stratification structures in inland waters. Due to the diverse environments of lakes - defined by local morphological,...
Article
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Double diffusion in lakes and oceans can transform vertical gradients into staircases of convectively mixed layers separated by thin stable interfaces. Lake Kivu is an outstanding double-diffusive natural laboratory with > 300 such steps over the permanently stratified deep basin. Here, we use 315 microstructure profiles (225 measured in Rwanda and...
Chapter
Aquatic physics in inland water is a crucial subject for studying aquatic ecosystems. Transport and mixing are of tremendous importance for the pace at which chemical and biological processes develop. Recent observations allow to distinguish mixing and transport processes in stratified lakes and reservoirs. The surface and bottom boundary layer are...
Article
There is increasing interest in using waterbodies as renewable energy sources to heat and cool buildings and infrastructure. Here, we estimate the potentials for heat extraction and disposal for the main lakes and rivers of Switzerland based on acceptable temperature changes in the waterbodies, and compare them to regional demands. In most cases, t...
Conference Paper
Full-text available
EXTENDED ABSTRACT Introduction In ice-covered enclosed waterbodies, the primary source of energy is supplied by the fraction of solar radiation able to penetrate across the ice and reaches waters usually found below the temperature of maximum density (Kirilling et al. 2012). In this scenario, the radiative buoyancy flux, í µí»· " , works directly t...
Article
Ice-covered waterbodies are far from being quiescent systems. In this paper, we investigate ice-covered freshwater basins heated by solar radiation that penetrates across waters with temperatures below or near the temperature of maximum density. In this scenario, solar radiation sets a radiative buoyancy flux, $\unicode[STIX]{x1D6F7}_{r}$ , that fo...
Article
Full-text available
Pumped-storage (PS) hydropower plants are expected to make an important contribution to energy storage in the next decades with growing market shares of new renewable electricity. PS operations affect the water quality of the connected water bodies by exchanging water between them but also by deep water withdrawal from the upper water body. Here, w...
Article
Phytoplankton growth depends on various factors, and primarily on nutrient availability, light and water temperature, whose distributions are largely controlled by hydrodynamics. Our main objective is to analyse the link between spatial and temporal variability of surface water temperature and algal concentration in a large lake by means of remote...
Article
Full-text available
Thermal responses of inland waters to climate change varies on global and regional scales. The extent of warming is determined by system-specific characteristics such as fluvial input. Here we examine the impact of ongoing climate change on two alpine tributaries, the Aare River and the Rhône River, and their respective downstream peri-alpine lakes...
Article
Full-text available
We investigate the impact on remote sensing reflectance by the vertical non-uniformities of water constituents. Reflectance simulated for 210 pairs of in situ measured chlorophyll-a and turbidity profiles (z = 0–20 m) from Lake Geneva are compared to simulations for uniform constituent gradients and non-uniform profiles approximated by Gaussian cur...