Work

Lake-water-temperature regulation under diurnal and annual cycles of environmental forcing, Agamon Hula, Israel

Year: 2025

Type: article

Abstract: Water temperature regulation is defined by a balance between the rate of change in stored heat and incoming and outgoing heat fluxes. Various approaches have been suggested to identify the key variables that govern this process, but most do not include direct expressions derived from long-term measurements. Here, we examine the impact of environmental forcing (radiation, wind speed, and air properties) on the thermoregulation of a shallow lake (Agamon Hula, Israel) using two years of continuous direct measurements with an eddy covariance tower. Using these direct observations, we accurately determine the equilibrium temperature by solving the heat equation for negligible changes in stored heat, revealing its dependence on environmental forcing. The relationship between water and equilibrium temperature is explained by the ratio between the lake's thermal response time, which depends linearly on lake depth, to the timescale of environmental forcing, that was identified using the Fourier method. We explain the resemblance and variability between both temperatures by low and high ratios between response time to annual and diurnal cycles, respectively. These are reinforced by negligible change in stored heat under the intra-annual forcing, as opposed to large oscillations in heat storage for the intra-diurnal cycle. We leverage the results to study expected annual water temperatures under different environmental scenarios, and the role lake depth has on intra-diurnal water temperatures. Additionally, during an intense three-day cyclone, we observed a similarity between water and equilibrium temperature, attributed to the lake's shorter response time relative to the cyclone's timescale.

Source: Journal of Hydrology

DOI: 10.1016/j.jhydrol.2025.133142

Authors: Guy Tau, Yehouda Enzel, Hamish McGowan, Vladimir Lyakhovsky, Nadav G. Lensky

Institutions: Hebrew University of Jerusalem, Geological Survey of Israel, The University of Queensland

Language: English

Topic: Aquatic Ecosystems and Phytoplankton Dynamics

Subfield: Environmental Chemistry

Field: Environmental Science

Domain: Physical Sciences

SDGs: Climate action, Clean water and sanitation

Open Access status: hybrid

Estimated APC paid: $4,030