On Groundwater Travel Times in Granite and Gneiss

Abstract

A prudent, structured porous medium approach, based on first arrivals, is suggested for calculation of travel times. Limiting breakthrough curves for variable channels are derived from flow rates and channel volumes. These represent hydraulic conductivities and porosity factors in conductive rocksections. Tracer tests indicate high porosity, which rule out standard parallel plate and tubular channels. Site-specific fracturing emphasizes structural control and the need for large-scale interference tests. Retardation factors directly enter the breakthrough equation. They reflect nuclide interaction with stationary solids. The channel volumes and contact areas involved also control fluid flow and the breakthrough of non-sorbing tracers.