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Seasonal and long-term export rates of nutrrients with surface runoff in the river Jorka catchment basin (Masurian Lakeland, Poland)

Rybak J.

Polish Journal of Ecology

2002

Vol. 50, nr 4

439-458

In the Masurian Lakeland a medium size catchment basin of the Jorka river-lake system (about 65 km ^2) was studied intensively in 1996-1998 (April-October) and compared with the data from the late 1970s. Nutrients (TP, TKN, N-NO3) and chlorides were monitored in 15 short lakeshore streams draining small subcatchments that differed in land use. The annual and monthly concentration values of nutrients were measured as well as the annual load in kg ha^-1 year^-1. The data indicate that in a mosaic, hilly region the export rates from the diversified small catchments of both TP and TN tend to be low, lower than in other, non-mosaic areas; the values of export rates are mainly dependent on the discharge in the subcatchments; that is why the values for 1998 and/or 1997 were usually lower than for other years. There is a tendency to lower concentration for nutrients (including chlorides) and export rates in the subcatchments objected to low impact of agriculture (forest, wetland) than in the subcatchments dominated by cropland. Extremely high values were found for a few catchments with cropland, additionally polluted by sewage disposal in the vicinity.