NUTRIENT LOAD IN THE SULA RIVER BASIN AND MEASURES TO MITIGATE ITS EFFECTS

Nitrogen and phosphorus enter water bodies from point and diffuse sources. In the practice of water resources management in Ukraine, attention has so far been paid primarily to point sources, whereas the role of diffuse sources has long been ignored by researchers. To take into account the role of diffuse sources, modelling approaches are used worldwide. Therefore, the paper presents the calculation of the nutrient load of the Sula basin by two different methods - the mass balance method and the MONERIS model. According to the mass balance method, the emission in the Sula catchment is 921.2 t · year-1 for nitrogen and 312.9 t · year-1 for phosphorus. According to the MONERIS model, the total nitrogen emission is 1,809.8 t · year-1, and the phosphorus emission is 196.2 t · year-1. Based on the calculations, effective tools for reducing the anthropogenic load on the Sula catchment were proposed, in particular the implementation the Nitrate Directive at the national and regional levels, the conduction an environmentally oriented dialogue between state institutions, local governments, water users and farmers. It was also proposed to create a unified hierarchical system for collecting qualitative and operational information on the environmental situation within the catchment basins, as well as to establish a system for measuring chemical nitrogen and phosphorus flows at all eight gauging stations within the Sula basin. Specific measures to reduce the anthropogenic load in the Sula catchment include: improving the quality of sewage systems; reducing the use of fertilisers; reducing the share of arable land by converting it to pasture and forest; implementing organic farming; establisihing coastal protection stripes and strictly enforcing them; and restoring natural wetlands and natural river channels. The MONERIS model has shown that the greatest reduction in nitrogen and phosphorus emissions is possible through the use of contour ploughing and intercropping.