Abstract
Long-term changes in air and water temperatures and the resulted stratification phenomena were observed for Soyang Lake (SY), Paldang Lake (PD), Chungju Lake (CJ), and Daecheong Lake (DC) in South Korea. Non-parametric seasonal Kendall and Mann-Kendall tests, Sen slope estimator, and potential energy anomaly (PEA) were applied. The lake surface water temperatures (LSWTs) of SY and DC increased at the same rate (0.125 °C/y), followed by those of CJ (0.071 °C/y) and PD (0.06 °C/y). Seasonally, the LSWT increase rates for all lakes, except PD, were 2–3 times higher than the air temperature increase rates. The lake stratification intensity order was similar to those of the LSWT increases and correlations. SY and DC displayed significant correlations between LSWT (0.99) and PEA (0.91). Thus, the LSWT significantly affected stratification when the water temperature increased. PD demonstrated the lowest correlation between LSWT and PEA. Inflow, outflow, rainfall, wind speed, and retention time were significantly correlated, which varied within and between lakes depending on lake topographical, hydraulic, and hydrological factors. Thus, hydraulic problems and nutrients should be managed to minimize their effects on lake water quality and aquatic ecosystems because lake cyanobacteria can increase as localized water temperatures increase.
Highlights
Surface water temperature is one of the most important factors for water quality [1]
The lake surface water temperatures (LSWTs) increases as air temperatures rise as a result of climate change, influencing lake stratification, aquatic habitats, and water quality
The effect of rising LSWT due to longterm increases in air temperature on stratification intensity in Soyang Lake (SY), Paldang Lake (PD), Chungju Lake (CJ), and Daecheong Lake (DC) was investigated in this study
Summary
Surface water temperature is one of the most important factors for water quality [1]. Among the numerous factors impacting lake surface water temperature (LSWT), the nearsurface (at elevation 3.4 m above site) air temperature plays a critical role [2,3]. Observations show that inland water bodies are increasingly warming worldwide, with the LSWT increasing at faster rates than the oceans [4]. Lake warming can be higher than that of the surrounding air temperature [5], at mid-latitudes. Paerl and Paul [6] found that the LSWT increases the vertical stratification intensity in freshwater and marine systems. Stratification begins early in spring and continues through summer in freshwater environments, while destratification occurs later in fall [7,8,9]
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