Integrated Assessment of the Southern Bug River Basin Water Quality and Calculation of their Self-Cleaning Capacity

Abstract

The long-term dynamic of the integrated quality index values of the Southern Bug during 2000-2016  was heterogeneous, but the general trend indicated a slight increase due to the sanitary-ecological index and pollution index. The highest level of water pollution was observed in Khmelnytsky city and Alexandrovka settlement. To assess the self-purification capacity of surface waters, the hydrological zoning of the basin was taken. According to it three regions were identified by the types of intra-annual runoff distribution: Verkhnyobuzky, Serednyobuzky and Nizhnobuzsky. The obtained results of EC coefficient calculations for mineral nitrogen compounds show the inability of rivers to self-purify for Verkhnyobuzky and Serednyobuzky regions. Instead, the ability to self-purify is preserved for phosphorus compounds.Using the nonparametric Mann - Kendall test allowed to estimate the long - term trend of nutrients for the Nizhnobuzsky hydrological region. Trends N-NO₃^-, N NH₄⁺and Р-РО₄^3- are characterized by positive values of the statistical parameter, which means the increasing of these elements’ concentrations.

Rivers of the Southern Bug basin are classified as "good, clean enough". The main ecological and hydrochemical problems of the river are pollution by nutrients and indicators of toxic action.