Changes of nutrient concentrations in water sensitive to nitrate pollution from agricultural sources in the Samica Stęszewska river catchment

Changes of nutrient concentrations in water sensitive to nitrate pollution from agricultural sources in the Samica Stęszewska river catchment.The aim of this study was to evaluate the surface water quality during the fi rst period of measures undertaken to reduce nitrate concentrations in the nitrate vulnerable zone.The study was carried out in the upper part of the Samica Stęszewska catchment, located in the Wielkopolska region (western Poland), designated by the nitrate directive as a nitrate vulnerable zone (Nitrate Directive 91/676/EC).Water samples were taken at nine control points from February 2003 to December 2007.The results indicate that nitrate pollution reduction measures taken in the nitrate vulnerable zones were ineffective in reducing this type of pollution.Water quality was poor at almost all of the monitoring points, and based on nitrate concentrations, water quality was classifi ed in classes IV or V.The only exception was in the outfl ow from Lake Niepruszewskie, where water quality was classifi ed as either class I, II or III.Also water quality in Lake Niepruszewskie was extremely eutrophic.Our results indicated a role of Lake Niepruszewskie as a nutrient sink reducing pollution from the catchment.