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Seasonal concentration time of hydrological drought in Poland

100%

Tomaszewski E.

Geography and Tourism

2017

tom 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.

Charakterystyka sieci rzecznej małej zlewni położonej w strefie krawędziowej Wyżyny Łódzkiej

63%

Bartnik A. , Tomaszewski E. , Uniwersytet Łódzki W. B. i. N. o. Z.

tom 5

The hydrographical network is a phenomenon under constant time and space changes. These ch_anges have seasonal and multi-annual character. The dynamics of this phenomenon needs estimation not only of the network itself but also of the water moving in it. This problem becomes particularly important in the case of the areas located near urban grounds which are under intense anthropopression. It is possible then to conclude of progressive influence of human activities after recognizing of the natural factors forming hydrographical network. The Dzierżązna drainage basin was explored up to the Swoboda closing profile (42,9 km2). It is located in the northern Łódź Upland part and is drained by the Moszczenica river system (fig. l). The southern boundary of the basin is determined by the urban Zgierz suburbs. Exactly this place in Malinka, there are springs of Dzierżązna river. Hydrographical network explorations were carried out basing on the topographic map in the scale 1:25 000. Thus the obtained data were updated and verified in the field in July 1998. Analysis of the river network parameters was carried out in the capacity of a drainage density (Wilgat's and Neumann's method) and a degree of an orderly arrangement (verification of the Horton's theory after the Strahler's classification) - fig. 2, 4, tab. l, 2. The authors also made detailed estimation of each stream: a river long fall, sinuosity and development (fig. 3, tab. l). Estimation also concerns time in which water running the channels reaches the closing profile and concerns the discharge rate as well. Their space layout is represented on the maps - fig. 5, 6. In the final stage of the study the authors tried to evaluate the running water resources basing on the resources momentum measure. Thanks to using the mentioned above procedure it was possible to take account the dynamics of the resource processes, because physical unit of the presented measure is (m^4 x S^-l) They also estimated degree of concentration of the resources in the river system (fig. 7, 8).

Artykuł zawiera charakterystykę sieci hydrograficznej zlewni Dzierżąznej - po wodowskaz w Swobodzie. Ocenie poddano parametry sieci, czas dobiegu wody korytami do profilu zamykającego, jak również wielkości przepływów. Określono także zasoby wód płynących i ich koncentrację na podstawie miary pędu zasobów.