Component-Oriented Approach to the Construction of a Model of Runoff Formation and Export of Chemicals from River Catchments: Case Study of Tributaries of the Cheboksary Reservoir

The first stage of creating the foundations of component-oriented modeling of hydrological and geochemical processes in catchments has been implemented. The potential of a system of related and` for some processes, interchangeable, models of different levels of discreteness, intended for describing various processes of formation of biogenic element runoff from reservoir catchments, have been demonstrated. The models developed at the Institute of Geography, the Institute of Limnology, and the Institute for Engineering and Environmental Problems in Agricultural Production have been used. The proposed set of models allows selecting a number of algorithms optimally adapted to solving a problem under conditions of often limited initial data. The selection of individual blocks of the system, their integration into a single model for subsequent calculations of nutrient input with varying degrees of detail are shown for the catchments of the rivers of the Cheboksary Reservoir basin: the Linda (1681 km²) and the Kudma (3246 km²), flowing into the Volga River upstream and downstream of Nizhny Novgorod. Examples of model synthesis are given for solving the problem of predictive assessment of river runoff changes taking into account its distribution parameters on experimental catchments in the future, the problem of calculating the average annual nutreint export by different types of runoff from catchments, the problem of assessing the intra-annual distribution of nitrogen and phosphorus losses of agricultural origin on the studied catchments using calculations of the runoff hydrograph components taken from a hydrological model. It is shown that the proposed method of predictive assessment of changes in runoff from a river catchment under the influence of climate change can be used to calculate not only the general trend of changes in runoff characteristics, but also to assess the runoff distribution parameters in the future.