Flow and Transport in Fractured Aquifers: New Conceptual Models Based on Field Measurements

We derived new equations of fracture aperture (or tube diameter) as functions of a tortuosity factor that can be used in discrete models and even in continuum equivalent models to simulate fluid flow and pollutant transport in fractured aquifers. MODFLOW/MT3DMS water velocity predictions have been compared with those obtained using a specific software application which solves flow and transport problems in a 3D set of parallel fissures. The results of a pumping/tracer test carried out in a fractured limestone aquifer in Bari (Southern Italy) have been used to calibrate advective/dispersive tracer fluxes given by the applied models. The mean tracer velocity given by a breakthrough curve was greater than values predicted by continuum models. This discrepancy increased when the hydraulic conductivity of the considered fractured medium decreased. Successful simulations of flow and transport in the fractured limestone aquifer are then achieved by accommodating a new tortuosity factor in models. The importance of the proposed tortuosity factor correction lies in the possibility of taking into account the effective tracer velocity during flow and transport simulations in fractures even when using a continuum model.