Impact of climate change on water resources in lowland Poland

In this study, climate change was described by area-averaged annual precipitation totals and area-averaged mean annual temperature values in each catchment area, while water resources were described by mean monthly specific discharges in these catchments. Thirty-seven catchments located entirely in lowland areas of Poland were selected for the analysis. The research was conducted based on data from hydrological years 1961-2021. In order to compare changes in annual precipitation totals and mean annual air temperature values with changes in annual mean specific discharge, linear trends of the mentioned variables were determined. The effect of precipitation totals and air temperature on specific discharge in individual catchments was determined using multiple regression. Statistically significant increase in the value of mean annual air temperature was recorded for all studied catchment areas. In none of the examined catchments were the changes in annual precipitation totals statistically significant. Analysis of the time trends of specific discharge showed statistically significant decreases in their annual mean values in almost half of examined catchments. The correlations between specific discharge, air temperature and precipitation totals are not very strong, which is mainly due to the strong impact of other, anthropogenic factors on water management.The greatest negative changes are observed in the central part of Poland. Specific discharge is more strongly dependent on precipitation totals than on temperature, with the effect of air temperature only being reflected in the volume of water resources after a certain period of time.