Summary:

The Dobczyce Reservoir is especially important because it is a source of potable water for the inhabitants of Krakow. The source of the reservoir feeding is the Raba river, whose catchment still lacks properly managed sewage disposal, therefore the water inflowing to the reservoir contains pollutants which decide about the insufficient water quality in the reservoir and to a considerable degree also determine the processes occurring in it, including eutrophication and overgrowing. In the work analysed was the loading of the Dobczyce Reservoir with biogenic compound load carried by the waters of the Raba river. The analysis based on tests of the Raba water quality and the flow volume on the inflow to the reservoir in the Osieczany cross section. The tests covered the period from May 2003 until October 2005. Investigations of biogenic compounds concentrations were conducted with average frequency twice a month. Concentrations of NH₄, NO₂, NO₃,PO₄ and total P were determined. The loads of individual biogens were computed for days, months and years of the analysed period. The obtained results point to a considerable diversification of mean daily values of loads in the analysed years. They were the highest in 2005 for NO₃, NO₂ and total P, respectively: 1394.51, 15.32 and 127.64      kg ∙d^-1,whereas in 2004 for NH₄ and in 2003 for PO₄ assuming values respectively 835.08 and 355.50 kg ∙d^-1. The maximum daily loads of all researched biogens were registered in 2005, for NO₃,NH₄ and total P on 19 March, whereas for NO₂ on 11 June and for PO₄ on 10 August. Minimum daily loads were noted in 2003 and 2004; in 2003 for NO₃ and total P on 1 and 2 September, and for NH₄ on 27–30 November. In 2004 the minimum daily loads of PO₄ were detected on 1, 2 and 12-14 November and NO₃ on 11 December. The amount of total phosphorus load carried in during the year was referred to the area of the reservoir water table and compared with the value of assumed permissible load (01.0 g ∙m^-2∙d^-1) and dangerous load as stated by Kajak. The load inflowing to the reservoir exceeds the dangerous load more than twenty times and the permissible load over 40 times.