Past, present and future trends of nutrient loads within polish river catchments

Abstract

Eutrophication is identified now as one of the most serious problems in the Baltic Sea
environment. Almost 30 % of total emission of nitrogen compounds and up to 50% of
phosphorous is discharged via rivers form the territory of Poland. The major anthropogenic
source for waterborne nitrogen is clearly agriculture, while the biggest source of phosphorus
are point sources, mainly municipalities.
The aim of this research was, therefore the description of the possible actions able to reduce
nitrogen and phosphorus river loads with their spatial differentiation. In this study, spatial
modeling has been applied for the estimation of potential, application and effects of such
actions in the local and regional scale. GJS oriented model - MONERIS has been validated
and applied to calculate possible nutrient reduction. Furthermore the comparison of large
(Vistula) basin with regional one (Drwe;:ca) has been done with respect to their different
character of land utilization.
The investigations show that the efficient reduction of P-emission is possible by combining
two actions: full implementation of the National Programme of Municipal Wastewater
Treatment with the application of non-phosphate detergents. The possible reduction of total
phosphorus emission can be even 30-50 % in 2015 for whole Vistula catchment (comparing
with the present state).
The reduction of nitrogen emission is much more complex, because the majority of the Nemission is caused by diffuse sources - mainly agriculture. The most important ways are
emissions via tile drainage and via groundwater. In this case the most promising action is to
increase efficiency of fertilizers consumption and decrease of soil erosion. These goals can be
achieved by widespread implementation of Usual Good Farming Practice and promotion of
additional good practices described in Code of Good Agriculture Practice. Such policies lead
to substantial decrease of nitrogen surplus in agricultural land, which was identified as the key
factor influencing nitrogen river load.