ABSTRACT

ABSTRACT: Groundwaters in fractured rocks have variable hydrochemical and isotopic compositions which are indicators of how these low permeability flow systems have evolved over short and long timescales in response to normal evolution and to episodic perturbations which might have affected hydrodynamic stability. Interpreting these geochemical signals (for example, salinity gradients and groundwater ages) is problematic because the effects of external perturbations on stability are dispersed and diluted by subsequent evolution. Hydrochemical and isotopic data from groundwaters in fractured rocks in Britain and Sweden illustrate these interpretations and the associated uncertainties. Understanding the evolution of such groundwaters is of general interest and is specifically relevant to considering the stability of these groundwater systems with respect to waste containment and contaminant movement.