150-year daily data (1870-2021) in lakes and rivers unveils escalating surface water warming and intensifying heatwaves in the Pannonian Ecoregion (Hungary)

Water temperature is a pivotal factor in determining the health and functionality of both lotic and lentic water ecosystems. Bridging the gap between atmospheric influences and aquatic environments, this study embarked on a comprehensive reconstruction of daily surface water temperatures across lakes and rivers within the Pannonian Ecoregion over an extensive period of 150 years (1870-2021). Leveraging the sophisticated air2water and air2stream models, we meticulously mapped the thermal dynamics of these vital water bodies, providing unparalleled insights into their historical temperature trends. The analysis revealed a clear warming trend in water temperatures over the past 150 years, with lakes experiencing a higher increase (0.073°C/decade) compared to rivers (0.046°C/decade) between 1870 and 2021. Seasonal patterns indicated that winter and spring exhibited faster warming rates, followed by summer and autumn. Additionally, there has been a significant increase in the frequency, duration, and intensity of heatwaves in lakes and rivers, particularly pronounced in the last 30 to 40 years. These findings underscore the escalating impact of climate change on freshwater systems in the Pannonian Ecoregion, emphasizing the urgent need for mitigation measures. The insights from this study are invaluable for informing freshwater management practices, including fish habitat management and ecosystem modelling, to address the challenges posed by the changing water temperatures and heatwave dynamics.