Water quality patterns over the length of the Dnieper river

Introduction. The Dnieper River is the most important river of Ukraine, the water of which is used for many purposes, in particular, for drinking water supply. Human activity has an important impact on the Dnieper River, the main factors of which are the regulation of runoff and sewage water. In addition to that, the quality of water depends on some natural factors, among which the water runoff is the most significant one. Goal. The main goal of the investigation is to determine the main patterns of water quality over the length of the Dnieper River. Methods. The main sources of data obtaining for this investigation were the results of the monitoring of the State Agency of Water Recourses network. These data were processed using the statistical methods. The main attention was paid to the period of 2012–2017. Results. The investigated period for water runoff can be divided into 2 parts: one with usual water runoff (2012–2014) and another with insufficient one (2015–2017). The mean solids concentation alongside the Dnieper River during 2012–2017 change from 250 mg/dm3 near the border with Belarus to 320 mg/dm3 near the river mouth. There is reverse dependence of this parameter on the water runoff. The smallest solids content near Kyivska HPP is observed in July, near Kherson in March. Such delay in comparison to natural conditions and data of previous investigation can be explained by existence of reservoirs where the water velocity is very small. Moreover, during the last years with small runoff the runoff was less than usually. At the same time the colourity of water alongside the Dnipro river has the tendency to decrease. The chemical oxygen demand in the investigated part of the river doesn't change essentially but during the year period it changes almost twice. The largest meaning near Kyivska HPP ussually is observed in May–August, on the downstream it happens one or two months later. The important contaminators of the Dnipro river is the Bortnitska water treatment station which is located on the south-eastern suburb of Kyiv. Downstream the water quality is much worse than upstream. During the whole observation period started in 1993, the water quality hadn't change essentially. Conclusions. The data of observations provided by of the State Agency of Water Resourses make it possible to characterize spatio-temporal regularities of water quality alongside the Dnipro river. According to the available data the water quality for some parameters has the tendency to improve and for the others – deteriorating. During the whole observation period, started in 1993, the water quality didn't change essentially.