LEACHING OF NUTRIENTS FROM THE CATCHMENT AREAS OF SMALL RIVERS IN THE REPUBLIC OF TATARSTAN
Natural and human circumstances of catchment areas significantly affect the formation of biogenic elements and their content in the surface water bodies. The aim of this study was: (i) to determine the main factors that affect biogenic elements formation in catchment territories of small rivers in Tatarstan Republic; (ii) to calculate the transfer of these elements through the gauging section (closest to the mouth) of a number of small rivers of the republic; (iii) to analyze their content in the waters of the Kuibyshev and Nizhnekamsk reservoirs. The objects of the study were the small rivers of the Republic of Tatarstan, flowing into the Kuibyshev and Nizhnekamsk reservoirs. We used geographical, ecological, comparative, literary analysis to identify the main factors shaping the removal of nutrients from a catchment area. Also we identified features of biogenic substances that determine their circulation in the environment. Approaches to the development of predictive mathematical models of flushing the nutrients from farmland into water bodies were analyzed. It was found that not small rivers but the wastewater of large industrial centers located on the banks of reservoirs form the maim content of nutrients in the waters of the Kuibyshev and Nizhnekamsk reservoirs.