Summary:

Basing on four 49-year time series of daily flows in the Mała Wisła catchment, the influence of the adopted POT-type drought definition on the stationarity of four drought characteristics: drought starting time, inter-drought time , duration T and deficit V, as well as their mean characteristics were investigated. The drought definition depended on three parameters: p, Tmin and min, i.e., the mean percent exceedance time of the given threshold flow Qp (p = 60, 70, 80 i 90%), minimum drought duration T¬min and minimum inter-drought time min; (Tmin, min) = (7;7), (14;7) and (14;14) days. The mean characteristics exhibited regular (in some cases very regular) dependence on p. It was shown that the monthly average number of drought starting times has clear minimum in March, and the null hypothesis on the zero slope value of the time regression for the remaining three characteristics, , T and V may be accepted in most cases.