Climatic changes and value of anthropogenic load of watershed of the rivers can be main reasons. The article researched long-term changes in the chemical composition of rivers in Ukraine. Long-term changes in the chemical composition of the river waters of Ukraine were analyzed using the modernized Alekin classification (modernization was proposed by V.K. Khilchevskyi and S.M. Kurylo). The additions introduced by the authors to the basic classification of O.A.Alekin allow fixing the dynamics of changes in the chemical composition of natural waters by cations at the group level, as well as at a more detailed level, revealing quantitative changes in the relative content of class-forming anions (at the level of subtypes).
Taking it into account for the most relevant tasks which arise for hydrologists and hydrochemicals are considered to be determination of modern regularities of streamflow and hydrochemical regime in conditions of warming which happens and assessments of such changes for the perspective. The mineralization of water and concentration of the main ions in river waters change for many reasons. Studying has been executed on the Udaj river, Tur`ya river, Sula river. The trend of increasing salinity of river water is detection. Main changes are taking place in the spring. During period of supervisions there was growth of mineralization of water: Sula – from 440 to 1125 mg/dm3.The main factor there is an increased part of groundwater flow. In favor of this conclusion the following results of researches serve. The special executed calculations showed dependence between part of ground flow and chemical composition of water of the rivers.
Different classifications are used to systematize natural waters by chemical composition. Attempts to classify water in accordance with the general conditions by which their chemical composition is formed are known. For analysis of long-term changes of the hydrochemical regime in different phases of the water was found and application of the classification of Alekin (modernizated). Modernization does not touch the highest trait – class, but concerns groups and types, with the introduction of a new taxon – subtype. Modernization to the basic classification of Alekhin allow to fixed in detail the dynamics of changes in the chemical composition of natural waters by cations at the group level. At a detailed level, quantitative changes in the relative content of anions (at the level of proposed subtypes) can be fixed.
Verification of the modernized classification of O.A. Alekhin, made on 25 rivers of the Dnipro river basin. Rivers are located in different environmental zones, have different anthropogenic pressure and term of observations (40 – 60 years).
An attempt was made to apply the modernized classification to other types of natural waters – groundwater and atmospheric.
