ABSTRACT. – Main hydrological statistical characteristics of low water on the Someş/Szamos River. Water deficits in low water periods caused by dry periods leading to droughts often are accompanied by considerable damage in the Tisa/Tisza Basin. The Someş/Szamos river network (15.881 km2) is the secondary left bank tributary of Tisa. The catchment is shared by Romania (96%) and Hungary (4%). Daily streamflow data for the description of low flow conditions are available since 1950, namely 54 and 58 years long series for Satu Mare (RO) and Csenger (HU) consequently. Lower reaches of the river were considerable modified during the 19th century river training and flood protection works including the topology and geometry of channel network, while the hydrological regime of the upper hilly and undulating regions remained nearly natural until 1979. Discharge series until 1980 are or only slightly influenced, while the impact of reservoirs on the temporal distribution of runoff is felt after that period. Low water thresholds for the analysis of low water events were set by using different statistical approaches. Temporal changes of hydrological regime and low water events are described by the comparison of nearly equally long periods of observed daily flow series (30 and 28 years). Time independent and time dependent block extreme statistics are used to describe low water distributions.
Key-words: minimum discharge, low flow periods, hydrological statistical analysis, transboundary rivers, water uses, discharge probabilities.
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