6 Quality Assessment of Water Resources of River in Poland
129
Fig. 6.3 Spatial diversity of average BOD 5 (mgO 2 /L) in Polish river catchments and subcatchments
in 2010–2015 (own elaboration based on data from Voivodeship Inspectorates for Environmental
Protection). Explanations: catchments and subcatchments numbered as in Tables 6.2, 6.3, and 6.4
the Mazurskie Lakeland (the Pisa and Omulew catchments); and the Suwalskie Lakeland (the Czarna Ha´ ncza catchment). Average total nitrogen in the rivers of these
catchments did not exceed 1.64 mgN/L. The region with the highest concentrations of
total nitrogen is Wielkopolska. The high content of nitrogen compounds in the rivers
of the Obra Canal, middle Warta, Prosna and Wełna catchments is mainly caused by
intensive farming. The impact of agriculture on nitrogen compound contents in the
rivers is confirmed by high nitrate concentrations in drain water and drainage ditch
water [5].
In the catchments of the Kłodnica, Ner and Nurzec rivers, elevated nitrogen
compound concentrations mainly result from their inflowing from point sources of
pollution.
In terms of content in Polish rivers, phosphorus compounds were spatially
distributed similarly to nitrogen compounds (Fig. 6.6). The lowest total phosphorus
concentrations (< 0.099 mgP/L) were found in: the mountain and foothill rivers of the
Carpathians (the Soła, Skawa, Raba, Dunajec, Wisłoka and San river catchments); the
129
Fig. 6.3 Spatial diversity of average BOD 5 (mgO 2 /L) in Polish river catchments and subcatchments
in 2010–2015 (own elaboration based on data from Voivodeship Inspectorates for Environmental
Protection). Explanations: catchments and subcatchments numbered as in Tables 6.2, 6.3, and 6.4
the Mazurskie Lakeland (the Pisa and Omulew catchments); and the Suwalskie Lakeland (the Czarna Ha´ ncza catchment). Average total nitrogen in the rivers of these
catchments did not exceed 1.64 mgN/L. The region with the highest concentrations of
total nitrogen is Wielkopolska. The high content of nitrogen compounds in the rivers
of the Obra Canal, middle Warta, Prosna and Wełna catchments is mainly caused by
intensive farming. The impact of agriculture on nitrogen compound contents in the
rivers is confirmed by high nitrate concentrations in drain water and drainage ditch
water [5].
In the catchments of the Kłodnica, Ner and Nurzec rivers, elevated nitrogen
compound concentrations mainly result from their inflowing from point sources of
pollution.
In terms of content in Polish rivers, phosphorus compounds were spatially
distributed similarly to nitrogen compounds (Fig. 6.6). The lowest total phosphorus
concentrations (< 0.099 mgP/L) were found in: the mountain and foothill rivers of the
Carpathians (the Soła, Skawa, Raba, Dunajec, Wisłoka and San river catchments); the