Hydraulic or flow connectivity is important for conceptualising flow in geological media. Despite its importance there has, however, only been one unambiguous attempt at defining it: ‘the joint probability that hydraulic conductivities at any two points, separated by a given lag vector (directional distance), fall above some relatively high value’ (Neuman, 2005). We suggest that whilst this definition may be appropriate to flow within a homogenous porous medium, its application to fracture systems does not account for the heterogeneous nature of flow at different scales in these systems. For example, within such systems exceedance of high hydraulic conductivities is no guarantee that two points are hydraulically connected. In this study we suggest that hydraulic connectivity in geological fractured media is investigated using all the parameters of the perturbation of a fluid, whether it be physically or chemically, and the resulting response of the fluid. In hydrogeological investigations, parameters of the perturbation could be, for example, recharge, the amount of groundwater abstracted or tracer added, while parameters of the impact could be the time until impact, the drawdown, and the direction and distance to where impact occurs. This approach is required because parameters of the perturbation and the response depend on the specific study, its geology and the investigation of hydraulic connectivity being undertaken e.g. a pumping test or a tracer test. In this talk we illustrate the importance of this approach for hydrogeological investigations and the parameterisation of flow, in systems where flow is shown to be intrinsically heterogeneous at different scales, the fractured and karstified limestones of Ireland.