Diagnostic variables in the study of conditions on migration of pollutants to underground water

Abstract

The suscepcibility of the aquifers to pollution depends upon numerous factors, including hydrogeological conditions and the nature of polluting substances. The paper presents the procedure for the establishment of the optimum set of physically justified and uncorrelated diagnostic variables, describing the process of pollution transport through the zone of aeration to underground water. On the basis of the existing methods and models, as well as equations used to describe the process of transport of humidity and pollution in the soil, the set of six physically justified variables was selected, characterising the best the movement of pollutants in the aeration zone (in-field water capacity of soil, soil humidity at the point of persistent withering of plants, filtration coefficient, depth of the groundwater table level, root zone depth, terrain gradient). The variables, represented through the form of numerical maps, were identified within the grid of uniform cells overlaid on the catchment area. The study was carried out in the basin of upper Wilga- the right-hand tributary of Vistula, representing the conditions of the environment of the Middle Polish Lowlands. The matrices of spatial information, prepared in this manner, were reduced with the aid of the principal component analysis. Consequently, the original set of diagnostic variables was replaced by three new synthetic variables, not correlated among themselves (the principal components), namely the indicator of sorption conditions (associating filtration coefficient, in-field water capacity and humidity of persistent withering), the indicator of infiltration distance (linked with the depth to groundwater level and the thickness of the root zone), and the terrain slope indicator. The new iagnostic variables, established in this manner (the principal components) may be made use of in determination of susceptibility of the aquifers to pollution and in classification of the catchment area with respect to conditions for migration of substances to underground waters