Role of Lake Symsar in the reduction of phosphorus concentration in surface runoff from agricultural lands

Abstract

Abstract The study was aimed at assessing the role of Lake Symsar in the reduction of phosphorus delivered mainly by the Symsarna River. Studies were carried out since March 2011 till October 2013 in the catchment basin of Lake Symsar situated in north-eastern Poland. Every month surface water samples representative for the catchment were taken for phosphate-phosphorus (PO4-P) and total phosphorus (TP) analyses. Obtained results were analysed with the distinction of vegetative and non-vegetative season. Lake Symsar is the last water body in the Symsarna River system. The river divides the lake into main basin and a bay part. Concentrations of PO4-P were higher by 17% in the former than in the latter part, TP concentrations showed reverse proportions. The highest concentrations of TP were noted in a forest stream and the highest concentrations of PO4-P in the Tolknicka Struga. Reduced concentrations of both P forms were found in waters of the Symsarna River downstream its outflow from the lake. With respect to the concentrations of PO4-P and TP, waters of the Symsarna River up- and downstream the lake were ascribed to the 1st class of water quality. Through-flow Lake Symsar improves the quality of waters (the Symsarna River and smaller streams) draining agricultural catchment by the reduction of concentrations of phosphorus compounds.