Bypass- and matrix flow produce interflow and contribute to groundwater protection

Author: Klaus-Peter Seiler

Received 19 November 2002, accepted 19 February 2003.

Abstract

In the unsaturated zone of Tertiary and Quaternary sediments of Bavaria bypass-flow may get significant as compared to matrix-flow. Tracer experiments with Deuterium prove that bypass-flow exceeds flow velocities of 0.5 m/d and matrix-flow ranges between 0.7 m/year (Loess), 1.2 m/year (Tertiary gravels and sands) and 2 m/year (quaternary gravels). In areas with a deep groundwater table and unconsolidated rocks bypass-flow penetrates to depths of less than 1m (fine sands) and more than 3m (gravels) below ground before it either incorporates into matrix-flow or generates interflow in hilly areas. - Bypass-flow depends upon geologic, biologic, pedologic and in arable lands also from anthropogenic factors. In hilly terrains, bypass- and interflow enhance the export of agrochemicals from the effective root zone; contrary, in flat lands bypass-flow accelerates the input of agrochemicals to groundwater. - Bypass-flow seems to be strongest under wet and dry soil moisture conditions at the surface and more dominant in fluvial than in lake and marine sediments.