This work aims to estimate the pollution of water objects of St. Petersburg and the North-West of Russia in general. It is based on the multi-criteria assessment of state and stability of water ecosystems that allows to consider various parameters of ecosystem regimes known in Russian literature as the ASPID (Analysis and Synthesis of Parameters under Information Deficiency) method. General randomized criterion reduces the data on six groups of aqueous ecosystems' state (hydrological, atmospheric, rain water runoff, hydrochemical, hydrobiological, and additional). These groups totally incorporate 23 parameters and five classes of water quality identified in the North-West of Russia. Similar method was applied for the assessment of the Neva River.