ABSTRACT
Contaminant patterns in groundwater, as in soil, arise from spatial and temporal variations in the contaminant inputs, groundwater flow , and chemical interactions between the sediment (or bedrock) and groundwater. Groundwater and its associated dissolved and colloidal substances are transported along groundwater flow line s. Each groundwater flow line is a line whose tangent at any point is parallel to the groundwater flow velocity. Groundwater flow lines intersect perpendicularly with equipotential line s, i.e. lines along which the hydraulic potential remains constant. The network of groundwater flow lines and equipotential lines is called a flow net (Hubbert, 1940) and the volume bounded by arbitrarily selected flow lines is called a stream tube . This implies that the amount of water flowing through a stream tube is constant along the stream tube. Exchange of dissolved substances across the boundaries of a stream tube is limited and, by definition, occurs only due to molecular diffusion and transverse mechanical dispersion .
