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Seasonal concentration time of hydrological drought in Poland

Tomaszewski Edmund

Geography and Tourism

2017

Vol. 5, No. 2

17--26

The time of hydrological drought concentration was estimated based on Markham’s indices. The research material consisted of a series of daily discharges from the period of 1985-2014 obtained from 79 cross sections of stream gauges distributed along rivers in Poland. In the first stage of the research, low-flow episodes were identified at the threshold level of Q70%, derived from the flow duration curve. Drought streamflow deficit volumes were calculated and assigned to monthly intervals. On this basis, the hydrological drought concentration time index and the hydrological drought seasonality index were assessed for particular years and for the whole study period. Spatial and temporal analysis was carried out on both characteristics, paying particular attention to a number of factors determining the investigated phenomenon and the long-term stability of hydrological drought concentration time.

Intense precipitation and high river flows in Europe - observations and projections

Kundzewicz Z. W.

Acta Geophysica Polonica

2005

Vol. 53, nr 4

385--400

Several destructive floods have occurred in the last decade in Europe, causing record high material damage. The question of detection and attribution of changes in various flood-related indices attracts increasing interest. Among the mechanisms that can impact flood risk are changes in socio-economic systems, which influence terrestrial systems, and changes in the climatic system. The atmosphere's water holding capacity (and hence potential for intense precipitation) increases with temperature and more intense precipitation has been documented in the warming world. However, a general and coherent increase in high river flows has not been detected. Results of change detection studies of daily river flow in Europe show that the overall maxima (for the 1961-2000 period) occurred more frequently in the subperiod 1981-2000 than in the subperiod 1961-1980. Regional changes in the timing of floods have been reported in many areas of Europe, with increasing incidence of late autumn and winter floods (caused by rain) and fewer spring snowmelt floods. Also, the number of ice-jam related inundations has decreased. On the other hand, intensive and long-lasting summer precipitation episodes have led to disastrous floods in Central Europe (cf. the 1997 Odra/Oder flood, the 2001 Vistula flood, and the most destructive 2002 deluge on the Labe/Elbe), and river flooding has been recently recognized as a major hazard in the region. Significant differences between future projections and the reference period, indicating the likelihood of increasing flood hazard, have been identified in both intense precipitation and high flows.