Summary:

The article attempts to assess the precipitation impact on eutrophication process in selected lakes of Suwalsko-Augustowskie Lakeland (lakes: Necko, Rospuda Augustowska, Studzieniczne and Białe Augustowskie). Numeric model of eutrophication, defined in WASAP programme (Water Analysis Simulation Pro-gram), which is developed and worked on in USA Environmental Protection Agency, has been used in studies. The model has been developed on the basis of own investigations, which were carried on in 1998-2008 years as well as the rain-fall analyses, that were available in WIOŚ (Voivodship Inspectorate for Environ-mental Protection) materials and statistical Yearbooks. Using the calibrated model a simulation was made, in which estimated nitrogen and phosphorus loads, delivered to the lake's waters from precipitation, were increased and decreased and then, the concentration changes of total nitrogen, ammonium nitrogen, nitrate, total phosphorus, orthophosphate and chlorophyl ‘a' were observed in the model. Based on the obtained results, the role of precipitation in the eutrophication process of lakes was assessed.