G. Mihaylova, G. Kostadinova, G. Petkov

Abstract. The aim of the study was to assess the physical-chemical status of surface water in lower part of Toundja river (to the border with Turkey), on selected indicators of water quality (temperature, oxygen balance, pH, conductivity, ammonium nitrogen – N-NH , nitrite nitrogen – N-NO , nitrate nitrogen – N-NO , 4 2 3 phosphates – P-PO , BOD ) in accordance with the proposed Classification system (Consortium for Biomonitoring, 2010). The system is designed according to 4 5 the Water Framework Directive (WFD) of the European Union 2000/60/EC, whose main objective is to achieve “good water status for surface water bodies by 2015”. The assessment was carried out at water body level, taking into account the results for three groups of indicators: general, nutrients and organic pollutants. For the investigated area was found a “good” status for surface water bodies of semi-river type R5. Achieving the goal of “good” state for surface water bodies of river type R12 (large lowland rivers) is mainly related to reducing pollution from phosphates and nitrite nitrogen. This leads to a real risk of not achieving the WFD objective of “good physical-chemical status” of surface water, used for irrigation in agriculture and other economic activities.