Introduction. In mathematical modeling of regional water flow and water quality, it is necessary to consider the interaction of different components of a given flow and mass transfer between them. The water flow processes that are part of the hydrologic cycle differ from each other in their physical nature, and each of them has their own region of localization. The following factors make the main contributions to the formation of a water flow [1]: flow in streams and basins; pressurized and unpressurized filtration of subsoil waters in connected aquifers , the migration of moisture in the zone of incomplete saturation (aeration zone), overland runoff of rainwater, and the formation and thawing of the snow cover.Reliable mathematical models have been developed to describe individual processes in the hydrologic cycle and have long been used to solve practical problems [2, 3]. In the middle of the 1970s, researchers began to actively develop models that describe the coupling of fluvial and filtration flows [4--6]. At the beginning of the 1980s, results began to appear from mathematical modeling of water exchange processes on land with allowance for all relevant factors [1,[7][8][9]. Such models can be used to predict the regime for large river basins, irrigation and drainage systems, etc. However, the solution of environmental problems requires an evaluation of the quality of subsurface and surface waters.In this investigation, we propose a mathematical model to describe the transport of salts by coupled flows of surface water (streams and basins), soil water (the aeration zone), and subsoil water for large-scale objects characterized by complex hydrogeologic conditions.Given the current state of computer technology, it is not yet possible to solve the given problem as a whole on the basis of a single three-dimensional hydrodynamic model. We thus propose to use a modular approach to construct mass-transfer models. The approach involves the linking of hydraulic submodels of varying degrees of complexity which correspond to different physical processes [1]. The interaction between the components of a given water flow are modeled by source functions that enter into differential equations, internal boundary conditions, and parameters of the model determined during the solution of the problem. The overall model of mass transfer includes submodels which describe water exchange and water quality. It is assumed that salt transport has no effect on the flow of the aqueous phase.Modeling of Coupled Flows of Subsurface and Surface Waters. We are examining a bounded

Terrigenous reservoirs are studied by a joint analysis of processes of various physical nature. This study is urgent because new methods for formation evaluation (first of all, permeability) from electric and electromagnetic logging data are required. We propose a method for the complex processing and interpretation of time-lapse well logging electromagnetic measurements, which show the dynamics of processes in the well influence zone. The constructed electrohydrodynamic model of the borehole environment is used to estimate the hydrophysical (petrophysical) parameters of the formation.

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This paper considers a two-dimensional hydraulic model which describes gas or oil flow to a horizontal well with hydraulic fractures and takes into account the reservoir geometry and fluid flow between the reservoir and the well. A computational algorithm is proposed, and calculations for gas and oil reservoirs are performed. A comparison of the calculation results and the solutions of the corresponding problems in a three-dimensional formulation show that the calculations using the approximate hydraulic model yield reasonably accurate results.