Chemical and hydrobiological analysis of water quality of the Uzh river of Korosten district and the city of Korosten of Zhytomyr region was investigated. The influence of anthropogenic loads on the river eutrophication processes was estimated. The peculiarities of the course of eutrophic processes in the reservoirs of the Uzh river basin within the Korosten district and the city of Korosten have been established. As a result of research, it was found that phytoplankton in the surface waters of the river Uzh Korosten district was represented by diatoms, green, blue-green, euglenophytic, golden and dinophytic algae. Periods of their intensive reproduction were revealed for all departments of algae. Seasonal fluctuations of the content of biogenic elements of phosphorus and nitrogen dissolved in oxygen water, their influence on the development of certain departments of algae were revealed. Statistical modelling of the processes of development of blue-green, green and diatoms in the waters of the river Uzh Korosten district on the average values of their content for less than three years was conducted. Changes in the qualitative and quantitative composition of algae during the year were used to build the models. The obtained experimental data and their revealed features are generalized in the form of linear and nonlinear statistical mathematical models of eutrophication processes. The general appearances of the functions that describe these processes; numerical values of the coefficients of the function; graphs are constructed and modelling errors were defined.