Hydrography and hydrochemistry of the transboundary river Western Bug on the territory of Ukraine

Abstract

The analysis of the hydrographic network of the Western Bug basin on the territory of Ukraine. This basin is estimated according to the requirements of the EUWater Framework Directive and has 2,044 rivers. Classification of the rivers of the Western Bug by area of drainage basins has shown the following results: in this basin within Ukraine there is one very big river, in fact this is the Western Bug itself. There are also three large rivers – Poltva, Rata and Luha. There are also 30 medium and 2,010 small rivers (among which 1,966 rivers have a length of less than 10 km). Theleading role of natural factors in the formation of the hydrocarbonate-calcium ion composition of the river waters of the Western Bug basin is determined. The content of the main ions and the salinity of the river waters are distin- guished by a sufficiently clear seasonal character: a decrease in the spring flood and an increase in the low water level (mineralization of the water of the Western Bug – 497-573 mg/l). Mineralization of the Poltva River (the left tributary of the Western Bug), located in the same natural conditions, is significantly different: in the area of the city of Lviv (the upper reaches of the Poltva River), it reaches 784-871 mg/l, and at the estuary of the river (Busk city, at the confluence of the Western Bug) is slightly reduced - 613-670 mg/l, while in the chemical type of water, sulfates and chlorides appear. This situation is explained by the discharge of sewage from the city of Lviv into the Poltva River. In the regime of nutrients, microelements, and also specific pollutants in the water of the West Bug, no general regularities in their seasonal variations were found, which is associated with the significant idiosyncratic character of the influence of anthropogenic factors on the formation of their concentrations. We estimated the balance of substances, both natural and anthropogenic, which are carried out with the waters of the Western Bug from the territory of Ukraine (93%), as well as from the territory of Poland (7%) to the border with Belarus. The comparative methodological approach allowed us to make a quantitative assessment of the significant influence of the Poltva River on the formation of the chemical composition of the water of the Western Bug, especially in its upper part. The share of Poltva's water flow when it flows into the Western Bug is 58% of its water flow. At the same time, the share of the total ion flow is higher – 66%. The share of the discharge of individual principal ions reaches: 76% (Cl-),87% (Mg2 +) and 98% (SO4 2-). For nitrogen, this figure is 68%, for phosphates – up to 80%.