Hydrological methods in environmental flows. Is it really simple? a critical study of selected catchments in central Europe.

[Display omitted] • The effect of data record length on environmental flow calculation is presented. • Method 7Q10 is the less sensitive to environmental flow calculations. • Trend analysis should be the starting point for calculation of environmental flows. • Environmental flows have a significant impact on water resource availability. • Environmental flows are the starting point for sustainable water management. The paper presents the analysis of problems regarding the calculation of EFs using selected hydrological methods. It was conducted in 14 catchments in the Vistula and Oder River basins in Poland. The Kostrzewa, Tennant, Q 90% , and 7Q10 methods were used for the analysis. The analysis showed a significant trend in the hydrological time series. The sensitivity of different applied methods to time series length was shown. High differences were observed between environmental flow (EF) values calculated for periods defined by break points. The hydrological drought and its impact for EFs were also observed for half years in the period. Finally, different values of water deficit characteristics were presented depending on the method used for EF calculation. [ABSTRACT FROM AUTHOR]