The main problem of freshwater lakes in the world, eutrophycation represents the over-enrichment of water by nutrients (nitrogen, phosphorus) and has emerged as one of the leading causes of surface water quality impairment. It is a rapidly growing environmental crisis, and worldwide, the number of coastal areas impacted by eutrophycation phenomenon stands at over 500. This important pollution process sets off a chain reaction in the ecosystem, starting with an overabundance of algae and other aquatic plants, excess which eventually decompose, producing large amounts of carbon dioxide. This paper is the result of researches located in Romania, performed over a period of eight years (2012-2019), in the area of a representative natural dam lake of the country - Red Lake, from Harghita County. Our researches aimed the quality parameters of the Red Lake water, the eutrophication process indicators, and their over time evolution. In order to predict the evolution of the studied pollution phenomenon in time, we used the software package “Surface-water Modeling System SMS 13.0” – the complete surface water solution, which was approached for the first time by Aquaveo. This software provides a comprehensive graphical environment for numerical modeling of eutrophycation, and tools for site characterization, model conceptualization and graphical visualization.