The results of hydrochemical observations of River Hrazdan section within the boundaries of city of Yerevan for 2012-2015 have been generalized. Physico-chemical parameters, indices of mineral composition of water, nitrogen-containing mineral substances, nitrates and phosphates as well as heavy metals (Mn, Cu, Zn, Cr, Mo, Pb, Cd, Co, Ni and Hg) have been determined. The spatial (8 permanent stations), seasonal (high- and low water) and long-term (2002-2005 and 2012-2015) dynamics of hydrochemical parameters has been studied. Geochemical series of heavy metals have been constructed. Water quality was assessed in conformity with both national and international standards. The appropriateness of water for the purpose of water use has been determined. Spatial and temporal organization of the river by results of cluster analysis: a change in ionic composition of water, increase in total mineralization rate, wide variation in concentrations of parameters such as turbidity, nitrogen-containing substances, phosphates, heavy metals – indicates a dominant role of pollution in water quality formation. It is established that the 5th class water quality restricts protection and normal functioning of a river ecosystem, fish farming and - that is particularly important – irrigation. Hydrochemical investigations implemented employing diverse methodological approaches have indicated that a long-term impact of a big city with developed infrastructure and rather a low level of nature protection measures on River Hrazdan has brought to deterioration of water quality.