ASSESSMENT OF NUTRIENT LOAD ON THE PREGOLYA RIVER BASIN (VISTULA LAGOON CATCHMENT) FROM THE ANTHROPOGENIC SOURCES

Abstract

The catchment area of the Pregolya River is about 65% of the Vistula Lagoon drainage basin and occupied by Russia and Poland in approximately equal proportions. Nutrient load from the catchment largely controls the eutrophication processes of the lagoon ecosystem. Open statistical data (2011-2014) were used for evaluating the nutrient loads. At present, the nutrient load from the major anthropogenic sources (population, livestock, poultry and crop production) is 53,267 tons N/year and 16,424 tons P/year in the Pregolya River catchment. This results in loads of 23,032 tons N/year and 2,819 tons P/year when the removal of nutrients by the harvest is taken into account. It was found that the load from anthropogenic sources in the Polish part of the catchment higher than in the Russian part by a factor of three times for nitrogen and two times for phosphorus. The reason for this is that Polish territory is relatively more agriculturally developed. In the Kaliningrad Oblast agriculture declined in the 1990-2000's and now about 50% of arable lands are not used, which creates a potential for development. Currently there is a positive trend of the agriculture development and the "Strategy of socio-economic development of the Kaliningrad Oblast until 2020" is expected to increase arable land by 70%, the number of cattle and pigs by factors of 3.5 and 9.5, respectively. This creates a potential for significant increases of the nutrients loading and eutrophication of the Vistula Lagoon. The nutrient load from the anthropogenic sources in the Russian part of the catchment can be compensated greatly by using the manure as organic fertilizer replacing mineral fertiliser, as at present time 40% of available arable land in the Kaliningrad Oblast is sufficient for utilization of all manure originated locally at the maximum fertilization rate recommended by HELCOM. At the same time more than 80% of the wastewater in Kaliningrad Oblast is not sufficiently treated. This poses a great potential for nutrient load reduction. The calculations showed that equipment of Kaliningrad city with the modern treatment facilities will reduce the nutrient load by 1,400 tons N/year and 290 tons P/year.