Changes in the thermal regime of rivers in Poland with different sizes and levels of human impact based on daily data (1961-2020)

The article examines thermal parameters of rivers during climate warming, focusing on quasi-natural rivers and those heavily impacted by humans. It compares two periods (1961-1992 and 1993-2020) based on daily water temperatures. Results show rivers warmed by 0.7-1.0°C in the second period, except those strongly polluted, like the Przemsza River, which cooled by up to -1.2°C. In quasi-natural rivers, the largest temperature rise occurred in spring (up to 3.5°C). In contrast, heavily impacted rivers showed lower, often negative changes. The study highlights the impact of climate warming and human activity on river thermal regime.