The Current State of the Problem of Assessing the Characteristics of Water Bodies Diffuse Pollution in Lowland Watersheds

A review of modern ideas about the nature and specifics of diffuse pollution of water bodies is made. The formation, movement, and transformation of water flows formed in watersheds during periods of snowmelt and rainfall saturated with dissolved and suspended substances is a complex multidimensional process distributed over the catchment area. The main factors in the formation of diffuse pollution of water bodies is the interaction of a complex of hydrological and geochemical processes, depending on the climatic features of the territory and the structure of land use in watersheds. The development of the chemical and biological industries has led to the entry into the natural environment of new pollutants alien to the biota, requiring new methods for monitoring and cleaning sources of diffuse and point pollution. In cities, the issue of entry and pollution of water bodies with a wide range of pollutants, including microplastics, is most acute. Suspension microparticles carry a significant proportion of priority pollutants for large cities (surfactants, oil products, heavy metals). It is noted that diffuse pollution of water bodies, which forms on various types of the underlying surface of watersheds, is not registered and is not regulated by any state water management or environmental department. The main reasons for this are the uncertainty of the consumer of diffuse runoff, the complexity of organizing its monitoring, and the incomplete understanding by state water authorities of its key role in pollution of water bodies due to insufficient scientific knowledge of the problem in Russia. The necessity of developing a modern scientifically substantiated network for monitoring diffuse runoff is noted. A review of modern models developed both in Russia and abroad, used to calculate the release of pollutants into water bodies using GIS technologies and advanced databases, is made. In a number of cases, an imbalance was noted in the degree of development of blocks describing the transfer of water, sediment and chemicals. Examples of the work of the Institute of Geography of the Russian Academy of Sciences in the modeling of diffuse pollution in the basin of the Cheboksary reservoir under the program “Improvement of the Volga” are given.