In the study, identification of hydrological drought was made, assuming that the low-flow period, which is a symptom of drought, is also a good estimator of its progression. The research was conducted in the upper Warta river catchment, for which the series of daily discharge for 12 gauging stations from the period 1971–2000 were available. The low-flow periods were identified on the basis of the constant threshold level, which corresponds to the 70th percentile of the flow duration curve (Q_70%). For the identified low-flow episodes, parameters pertaining to its duration, streamflow deficit, and flow dynamics have been estimated. The established identification and separation criteria made it possible to assess the simple and compound hydrological droughts unambiguously. Transformation of characteristics related to low-flow duration, relative drought streamflow deficit as well as low-flows contribution in the total number of gauging stations resulted in the evaluation of hydrological drought in terms of its severity and range. The characteristics, which are estimators of hydrological drought progression and recession rate, made it possible to define the determinants of the studied phenomenon and its time variability.