Impact of Anthropogenic Activities on River Water Quality in the Region of Lielupė River Basin District

The article analyses sources of point and scattered pollution and their change, also change of runoff and biogenic substances in the rivers Muša, Lėvuo, Tatula and Nemunėlis, located in a particularly sensitive karst region of Lielupė river basin district (RBD). The research was performed over the period from 1992 to 2009 with various intensity of anthropogenic activity. The most hazardous sources of pollution were determined by analytical and statistical methods, the tendency of their change was analysed also their impact on the river water quality was assessed. It was found that upgrading of wastewater treatment plants reduced the release of total nitrogen by 29 %, ammonium nitrogen by 13 %, nitrate nitrogen by 32 % and total phosphorus by 27 % over the period from 1992 to 2009. As the number of animals being bred dropped by 55 %, the load of total nitrogen and total phosphorus from livestock farms decreased by 51 %