The loads of nitrogen and phosphorus compounds flowing into the Goczałkowice Reservoir and out of it in the annual cycle were determined. The main source of biogenic substances was the River Vistula (78% N tot. and 69 P tot.). The intermediate pumping stations supplied altogether 12% N tot. and 18% P tot. The high loading of the Reservoir with phosphorus, amounting to 0.65 g P m-2 year-1 (including in the calculations the frequency of water exchange), exceeded about 4 times the admissible values.