Variability of physicochemical properties of water of the transboundary Poprad river

The results of five-year (2008–2012) hydrochemical research of the Poprad river, the right bank tributary to the Dunajec, were analyzed in the paper. The Poprad, 167 km long and with the catchment area of 2077.3 km², flows for over 100 km through the territory of Slovakia, along the length of 31.1 km is a transboundary river, whereas its 31.0 km long reach is situated in Poland. Concerning its abiotic character, it is an eastern upland river of type 15. The research was conducted in three measurement-control points: 1) located in Leluchów on the Polish-Slovak border at 61.1 kilometer of the river course, 2) in Piwniczna-Zdrój – 23.9 km and 3) in Stary Sącz – 2.9 km before the Poprad outlet to the Dunajec. 21 physicochemical indices and 2 microbiological indicators were assessed in the water samples once a month using referential methods. The paper assesses changes of water quality classes and its usable values along the analyzed Poprad river reach. Moreover, statistical differences between the values of individual indices assessed in various measurement-control points were estimated by means of Mann-Whitney U nonparametric test. On the basis of the conducted analyses of the empirical data it was stated that due to the physicochemical indices, water quality along the whole length of the analyzed river reach was good (class II) – in points 1 and 3 it was determined by mean concentration of total suspended solids, whereas in point 2 COD-Mn values.