Introduction:
Water is a convenient environment for the spread of pathogenic bacteria. Their presence may result from contact with water through soil, air, and animal and human activity. The identification of microorganisms allows us to determine the biological properties, the possible epidemiological risk, and the sanitary condition of the surface water.

Aim of the research:
To analyse the presence of microbiological indicators in selected water samples collected in autumn, winter, and spring.

Material and methods:
The research sites included three rivers and two water reservoirs located in Świętokrzyskie voivodeship. The water samples were tested based on the presence of coliform, mesophilic, and psychrophilic bacteria.

Results:
The presence of E. coli was confirmed in all water reservoirs, but values above the standard limit were confirmed in just three cases (Wisła, Bernatka, and Emerald Lake). The results show that the changing microbiological parameters of the analysed water samples can result from different factors. The large number of bacteria in water can come from other local streams and groundwater, human and animal activity, and especially from influx of domestic wastewater. The sanitary state of surface water in Świętokrzyskie is consistent with data from other Polish voivodeships published in the literature.

Conclusions:
Microbiological pollution of surface water in Poland is a constant and underestimated problem. It can be a serious epidemiological threat, especially in mild winters and warmer summers.