The Danube is a source of water for the household and industrial needs of Ukrainian population, industry and agriculture. The Danube waters are used for drinking centralized water supply in the cities of Kiliya and Vilkovo, as well as fisheries in the region. Therefore, it was important to carry out the “Environmental Risk Assessment for Drinking and Fisheries Use (on the example of the Danube River –the city Vilkovo)”. The purpose of the study was to evaluate the effectiveness of the application of the environmental risk criterion R on the basis of hydrochemical observations to verify the safety of drinking and fishery use. Analysis of environmental problems of the lower Danube River - Vilkovo; assessment of the environmental situation; calculation of water quality risk indicators according to the methodology of the Institute of Market Problems and Economic and Environmental Research of the NAS of Ukraine; establishing a link between water quality and risk is the finding of the research. It is established that the environmental situation is “critical” due to suspended substances, phenols, manganese and HCC for drinking water supply and “strained” through chromium, manganese, HCC, copper for fishery use. An assessment of the water quality by the modified Water Pollution Index (IWM) showed that the water is “moderately polluted” and “contaminated”. For both types of water use, normalized aggregated pollution indices were calculated taking into account the likelihood of a risk event occurring and R risk indicators were determined by year. It is established that there is a close linear relationship between WSS and R. It is shown that environmental risk estimates, based on the probability of exceeding concentrations of pollutants above the MPC, reflect well the ecological status of the water.

A method has been developed for quantitative and qualitative assessment of the risk of surface water pollution by nitrogen compounds based on the use of the indicator of the total content of inorganic nitrogen forms in water (Ninorg), that is,   This indicator is considered as the sensitivity coefficient kn. The choice of the indicator is dictated by the need to protect waters from pollution caused by nitrogen compounds during their flow from agricultural sources (Directive 91/676 /EU). The experience of developed countries has shown that nitrogen compounds deteriorate the quality of water and prevent the achievement of a "good ecological state" of water bodies. For territories with developed agriculture, it is important to establish environmental risks of damage depending on the degree of nitrogen pollution. Quantitative assessments of environmental risk are provided on the basis of a probabilistic approach. The risk was calculated as the product of the probability of a hazardous event occurring multiplied by the consequences of this event. The consequences of river pollution with nitrogen compounds were assessed as the ratio of the total concentration of nitrogen compounds (sensitivity index kn) to its threshold value (50 mg/dm3 or 11.3 mgN/dm3). In order to develop a scale for qualitative and quantitative risk assessment, relationships were established between the sensitivity indicators kн and the risk indicators R' for individual rivers, and for the study area as a whole, by means of spatio-temporal generalization. The probabilistic characteristics of possible environmental damage were determined on the basis of the obtained regression equations of the form R'=f(kn) and the statistical law of distribution of the risk value R'. The developed method will make it possible to determine the rank of the risk zone and the probability of getting into it, depending on the given sensitivity indicator kn

Виконана оцінка придатності вод р. Кучурган та Кучурганського водосховища за комплексом гідрохімічних показників за методикою Гідрохімічного Інституту (м. Київ, Україна) для потреб рибного господарства. Досліджена динаміка якості води у часі та просторі. За розрахунками комбінаторного індексу забрудненості за 2003-2018 роки на досліджуваних водних об'єктах води ІІІ-IV класу-«брудні» та «дуже брудні». На даному етапі можна зробити висновок, що вода р. Кучурган та Кучурганського водосховища є непридатною для рибогосподарського використання Ключові слова: комплекс гідрохімічних показників, комбінаторний індекс забрудненості, оцінка якості води

This article is devoted to the use of a mathematical model of a flood runoff for calculating rainfall runoff hydrographs from small catchments of the northwest coast of the Black Sea. The described model was tested and applied for the following catchments located in various geographical conditions, with various amounts of initial data: experimental catchments in Zacarpathian, the northwest of the Black Sea region-Ukraine and the Republic of Moldova, small catchments of the northern part of Vietnam, etc. This work was carried out on the basis of Moldavian Water-Balance Station databases. The development of a complex approach to a mathematical simulation of the formation of the processes of rain floods from small catchments is also given further investigation in this article. A brief description of the structure of a flood runoff spatial model from small catchments then provided. As well as this, the advantages of using radiolocation measurement of rainfall in the mathematical modeling of the formation of a flood runoff are shown. The results of construction runoff hydrographs confirm the possibility of applying this spatial model with the use of radar information. The optimization of model parameters was made with the data of 123 floods. The values of the quality criterion S/σ turned out not to exceed the value 0.8 in 81% of the considered cases of floods.