THE SEASONAL CHANGE OF WATER QUALITY PARAMETERS AND ECOLOGICAL CONDITION OF SOME SURFACE WATER BODIES IN THE NEMUNAS RIVER BASIN

The surface water quality analysis is very important in order to identify potential sources of contamination. The pollution of surface water can occur because of unauthorized discharge of a variety of materials or pollutants, and cultivated fields from which migratory pollutants are carried into the water bodies by melting snow. The current paper presents the results of quality indicators' analysis (oxygen saturation (dissolved oxygen) (mg O-2/l); an active water reaction, pH; suspended solids (mg/l); biochemical oxygen demand BOD7 7 (mg O-2/l); phosphate (mgP/l); nitrite (mgN/l); nitrate (mgN/l); ammonium (mgN/l); total phosphorus (mgP/l); total nitrogen (mgN/l); colour (mg/l Pt)) of some surface water bodies (the Dubysa, Reizgupis, Vilkupis, Kriokle Rivers and Prabaudos pond) in the Nemunas River basin. The research demonstrated that the majority of non- compliances and exceedances with values and the maximum allowable concentrations stated in the hygiene norms can be found in the Reizgupis River. According to the analyzed surface water quality indicators, the ecological conditions of the surface water bodies were determined.