Influence of Reservoirs on the Concentration of Nutrients in the Water of Mountain Rivers

The aim of the analysis was to demonstrate the role of reservoirs in shaping nutrient content (nitrates NO₃^- and phosphates PO₄^3- as well as ammonia NH₄⁺) in the waters of mountain rivers. Three Carpathian rivers with reservoirs in their courses were selected for the study: the Ropa River (Klimkowka reservoir), the Dunajec River (the Czorsztyn-Sromowce Wyzne reservoir complex) and the Raba River (Dobczyce reservoir). The basic criteria for the selection of the study objects for the investigation were: similar hydrological regime of the rivers and diverse parameters and functions of the storage reservoirs. The analysis of nutrient concentration was based on a long-term series of measurements (2004-2013). The reservoirs investigated generally contribute to an increase in nitrates in the rivers flowing below the reservoirs in particular months. The role of reservoirs in shaping phosphate and ammonia levels was not as evident as in the case of nitrates. The reservoirs are merely one of numerous factors that contribute to nutrient levels in the water of the mountains rivers. In the light of the analysis of nutrient concentrations in the surface water tested, it may be concluded that the reservoirs do not cause a clear and permanent deterioration of river water quality.