The study presents the results of a 6-year hydrochemical research conducted in three mountain microcatchments having similar physical-geographic and climatic conditions but differing in land utilisation. The study contains a qualitative assessment of surface waters in agricultural and forest areas on the basis of 12 physical and chemical properties tested in partial microcatchments of the Trybska Rzeka stream situated in the Polish part of Spisz. The assessment was made by the guaranteed concentrations method, and the concentrations were calculated by means of the probability density function. The results of the tests show that the insufficient quality of surface waters in mountain agricultural-forest microcatchments is most often caused by the excessive concentration of biogenes, namely nitrogen and phosphorus compounds (phosphates), exceeding the threshold values acceptable for a specific water cleanliness class.

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