Large lakes as sources and sinks of anthropogenic heat: Capacities and limits

Abstract

The goal of reducing carbon fuel and thereby saving energy will increase the use of lake water for heating and cooling of riparian infrastructures. This raises the question of which heat use designs meet the ecological and technical requirements for lakes, particularly in regard to climate warming. Thus, this study explores heat use effects on the temperature and stratification of a large, deep, temperate lake by applying the one-dimensional k-epsilon model SIMSTRAT to various forcing scenarios. Several design parameters, such as extraction and discharge depth, and their effects were assessed. Additionally, 21st century climate projections were used to evaluate the effects of climate change relative to those of heat use. Generally, the study showed only minor effects for a realistic heat demand of 62 W m 22 quite independent of the heat extraction/discharge modes. Mean water temperature changed less than 60.2 C as long as there was no discharge into the deepest layers. Water extraction and discharge at the surface had the least thermal influence. To relate to climate change, heat use was scaled up to 185 W m 22 . Resultant simulations showed that such (unrealistic) anthropogenic, lake-based ''thermal pollution'' would have a comparable influence to that of climate change. Conversely, heat extraction could damp or even compensate climateinduced warming. The present study concludes that (i) there are minor effects on water temperatures, stratification, and seasonal mixing due to heat use of up to 62 W m 22 and (ii) those influences are insignificant relative to the expected climate change.

Tributaries affect the thermal response of lakes to climate change

“…These in turn affect SSC and thermal regimes for rivers and their associated downstream lakes. Furthermore, here we show that local point sources of anthropogenic thermal pollution can have a major impact on the response of inland waters to climate change as previously suggested by Fink et al (2014b).…”

“…The model calculates heat fluxes and vertical mixing driven by wind and the internal wave field using a k − ε turbulence closure scheme. It has been adapted to and validated for multiple lakes including Lake Zürich , LG (Perroud and Goyette, 2010;Schwefel et al, 2016), Lake Neuchâtel , Lake Constance (Fink et al, 2014b;Wahl and Peeters, 2014) and LB (Råman Vinnå et al, 2017). The model contains seven tunable parameters, including p 1 (irradiance absorption), p 2 (sensible heat flux) and K (vertical light absorption) for heat flux adjustments from the atmosphere to the lake.…”

Optimizing the parameterization of deep mixing and internal seiches in one-dimensional hydrodynamic models: a case study with Simstrat v1.3

“…For the deep lakes (especially for Lake Geneva), the calibrated values of the α parameter tend to be higher than the ones found by previous studies, which ranged from 0.001 to 0.03 for large basins (Schmid and Köster, 2016;Fink et al, 2014b;Finger et al, 2007). There are several reasons that can explain this deviation.…”

“…Simstrat is a finite-difference buoyancy-extended reservoir model with k-ε turbulence closure. It has been extensively used to simulate water column temperature development under different conditions and over periods ranging from days to decades (Schwefel et al, 2016;Fink et al, 2014b;Stepanenko et al, 2014;Straile et al, 2010;Peeters et al, 2007Peeters et al, , 2002. The model performs equally well and in many aspects even better than other models, as shown in a comparison study simulating Lake Geneva (Perroud et al, 2009).…”

“…The stratified situation, associated with smaller vertical viscosity in comparison to horizontal viscosity, will favour BSIWs as well as up-and down-welling, the energy being absorbed by thermocline displacement and subsequently dissipated (Woolway and Simpson, 2017). We hypothesize that in 1-D models resolving BSIWs, too much wind energy is introduced and converted into BSIW in winter, incorrectly impacting deep convection patterns (Fink et al, 2014b).…”