The aim of the study is the identification of uncertainties to improve information support for the standards of permissible impact (SPI) elaboration for small rivers of the Sevastopol region. Materials and methods. The initial data were the results of surface water bodies monitoring in the Sevastopol region, other materials on the Chernaya River basin, characterizing the conditions for the formation of runoff and the quality of waters of small rivers. Monitoring data has been provided by the territorial bodies of Roshydromet, Rospotrebnadzor, Rosprirodnadzor and State Unitary Enterprise of Sevastopol for Water Use (SUES "Vodokanal"). The shortcomings of information support for the elaboration of SPI are revealed. Pollutants were ranked according to their importance for the ecosystem of the Chernaya River tributaries and distribution in water bodies, the water quality standards are substantiated. The list of pollutants in descending order of importance for the ecosystem includes: phosphates, nitrites, ammonium ion, BOD5, suspended solids, iron, manganese, copper, magnesium, calcium, nickel, zinc, phenols, sulfates, surfactants, oil products. The most common pollutants (indicators of pollution) in the tributaries of the Chernaya River are BOD5, nitrites, phenols, manganese, iron and copper (excesses of standards are recorded for almost all objects). MPC for objects of fishery importance were adopted as standards for SPI elaboration. The exception was BOD5, for this indicator the hygienic standard was used. Assumptions are proposed that allow solving the problem of elaboration SPI under conditions of incomplete information. The calculations of the runoff volume for the years of 50 % and 95 % security, SPIchem for priority pollutants on the main hydrological seasons were performed. Analysis of the results showed that SPI differ significantly by hydrological seasons (up to 48 times) and by each indicator of pollution for different tributaries, which is especially pronounced (more than 10 times) for the Uzundzha and Kalenda Rivers in terms of BOD5, iron, phenols and phosphates. The results obtained confirms the need for differentiated regulation of the permissible impact on individual tributaries of the Chernaya River. When developing the SPI for the small rivers of the Sevastopol region, normative-methodological, informational, large-scale and target uncertainties were identified. The assumptions proposed in the work make it possible to solve practical problems of management in the field of use and protection of water bodies, but do not reduce the relevance of measures aimed at improving the information support for the SPI elaboration. Measures aimed at improving the information support for the SPI elaboration includes: organizing access to the monitoring data of the territorial body of Roshydromet («Crimean UGMS»), increasing the frequency of observations on tributaries of the Chernaya River, organization of systematic observations in the background sections and in the zones of influence of diffuse sources of pollution.
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