The energy strategy calls for a further expansion of hydropower. This puts pressure on Swiss water bodies and water landscapes. At today's Eawag Info Day, some 200 experts from practice, research and administration will discuss how the various interests in water can be met in a sustainable manner and where the competition between these interests calls for priorities to be set. The Eawag researchers will demonstrate that it is not only a question of technical solutions, but also of social acceptance, for example when measures in favour of water ecology lead to an increase in the price of electricity. Read more
Toward an open access to high-frequency lake modeling and statistics data for scientists and practitioners – the case of Swiss lakes using Simstrat v2.1
One-dimensional hydrodynamic models are nowadays widely recognized as key tools for lake studies. They offer the possibility to analyze processes at high frequency, here referring to hourly timescales, to investigate scenarios and test hypotheses. Yet, simulation outputs are mainly used by the modellers themselves and often not easily reachable for the outside community. We have developed an open-access web-based platform for visualization and promotion of easy access to lake model output data updated in near-real time (http://simstrat.eawag.ch, last access: 29 August 2019). This platform was developed for 54 lakes in Switzerland with potential for adaptation to other regions or at global scale using appropriate forcing input data. The benefit of this data platform is practically illustrated with two examples. First, we show that the output data allows for assessing the long-term effects of past climate change on the thermal structure of a lake. The study confirms the need to not only evaluate changes in all atmospheric forcing but also changes in the watershed or throughflow heat energy and changes in light penetration to assess the lake thermal structure. Then, we show how the data platform can be used to study and compare the role of episodic strong wind events for different lakes on a regional scale and especially how their thermal structure is temporarily destabilized. With this open-access data platform, we demonstrate a new path forward for scientists and practitioners promoting a cross exchange of expertise through openly sharing in situ and model data.
Gaudard, A.; Råman Vinnå, L.; Bärenbold, F.; Schmid, M.; Bouffard, D. (2019) Toward an open access to high-frequency lake modeling and statistics data for scientists and practitioners – the case of Swiss lakes using Simstrat v2.1, Geoscientific Model Development, 12(9), 3955-3974, doi:10.5194/gmd-12-3955-2019, Institutional Repository
Energetics of radiatively heated ice‐covered lakes
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. Heat loss at the ice‐water interface depletes background potential energy at a rate that depends on the available potential energy dynamics. Expressions for relative energy transfer rates show that the pathway for solar energy is sensitive to the convective mixing layer temperature through the nonlinear equation of state. Finally, we show that measurements of light penetration, temperature profiles resolving the diffusive boundary layer, and an estimate of the kinetic energy dissipation rate can be combined to estimate the forcing rate, the rate of heat loss to the ice, and efficiencies of the energy pathways for radiatively driven flows.