Investigation of water temperature changes in the Hron River in the context of expected climate change

The water temperature is one of the physico – chemical indicator of water quality that plays a crucial role in affecting the biological processes in surface water. In the context of the climate changes, there are also changes in the temperature of the water in the streams. The paper presents an analysis of long-term data of the water temperature in the Hron River at two selected gauging stations: Banská Bystrica and Brehy, during the period of 1962–2020. The analysis was conducted using a long series of water temperature measurements. The aim of the study is to detect whether significant trends occur in the time series of water temperature. The first part of the paper dealt with the trend analyses of monthly and annual water temperature. The following section is focused on determination, investigation and evaluation of 1, 3-, 7-day maximum water temperatures. The impact of rising air temperatures on water temperature is critical for protecting water resources and ensuring water quality. In the last part of the study, the monthly water temperature of the Hron River at two gauging stations was modeled using air temperature. The best for Hron at B. Bystrica was the model: SARIMA(1,0,0)x(0,1,1) 12 + 1 regressor, and for Hron at Brehy the best was the model: SARIMA(1,0,0)x(1,0,2) 12 + 2 regressors, with a high correlation coefficient of 0.983 at B. Bystrica and 0.985 at Brehy. Results showed that a 1°C increase in air temperature caused the water temperature to rise by 0.35°C at Banská Bystrica and 0.57°C at Brehy, while a 3°C increase resulted in a rise of 1.05°C at Banská Bystrica and 1.75°C at Brehy. The study concludes that the SARIMA model can