Use of numerical methods for identification of hydrodynamic field and hydrogeochemical processes in the Quaternary multi-aquifer system

Abstract

The paper presents spatial analysis and numerical methods to describe the hydrodynamic and hydrochemical conditions in a groundwater system. The research was conducted in the northern part of the Białystok High Plane, eastern Poland, within a Quaternary multi-aquifer system. Spatial analysis was used for imaging the quasi-continuous structure of the system based on a discrete set of hydrogeological data. A high-resolution regional flow model was used to identify the groundwater discharge and discharge zones of the individual aquifers. Calculations have shown a marked asymmetry of the flow system. Deeply incised river valleys in the Niemen River basin more strongly affect the groundwater than the discharge zones in the valleys of the Vistula River basin. As a result, the underground watershed in deeper aquifers is clearly shifted westward in relation to the morphological watershed. The hydrodynamic conditions of the system determined by numerical methods were used to identify the points along the groundwater flow-path for the hydrochemical study. It was the basis for the identification of points located along the groundwater flow direction, which were used in the hydrochemical study. Computational schemes of water solution models were calculated for the quasi-equilibrium state of chemical reactions between the solution and the solid and gaseous phases. Presentation of the chemical reactions allowed determining the origin of changes in the concentrations of individual components dissolved in groundwater. It was found that kaolinitization, i.e. chemical weathering of feldspars and plagioclases is the basic process that most affects the groundwater chemistry.