CONSIDERING INFILTRATION DYNAMICS IN THE PROBLEMS OF REGULATING THE DISCHARGE OF POLLUTANTS WITH SURFACE RUN

Abstract

The article is devoted to the problem of calculating the volume of rainwater runoff from permeable surfaces in the task of limitation pollutant discharges into water bodies. The problem with the existing limitation methodology is that the calculation does not take into account the dynamics of changes in soil impermeability. The article considers different mathematical models of rainwater infiltration into the soil of the earth’s surface. It is noted that some infiltration models described in the literature have not been sufficiently tested and for this reason are not recommended for use in task of limitation pollutant discharges with wastewater. Also, according to the authors, a number of existing methods for calculating rainwater flow are inappropriate in these problems due to high computational complexity. The article pays attention to the Horton exponential infiltration model, widely presented in the scientific literature, and the calculation of the amount of rainwater runoff using the CN method. When using the Horton model, it is necessary to take into account the initial delay in rainwater runoff caused by two factors: possible high initial infiltration and filling of depressions on the surface with water. The formula for calculating the initial time delay of rainwater runoff is derived. It is noted that the problem of using the Horton model is the uncertainty of its parameters. This circumstance prevents its use in the task of rationing pollutant discharges with rainwater runoff, since this will require all water-using enterprises to conduct labor-intensive and costly studies of soil properties in the catchment area. The article provides a demonstration calculation of rainwater runoff flow using different methods using the example of the catchment area of the locomotive depot named after T.G. Shevchenko (Smela, Cherkasy region). Attention is drawn to the significant difference in the results of calculations using different methods. The authors conclude in favor of using the CN-method in the task of rationing discharges, which indirectly takes into account the dynamics of soil impermeability. The implementation of this proposal will require, firstly, changes to the existing methodological base for calculating maximum permissible discharges of substances into water bodies, and secondly, identification of the watershed surface of enterprises in accordance with the classification of the US Natural Resources Conservation Service.