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Long-term threats to groundwater quality arising at regional scale from the exploitation of deep groundwaters, and some ways to tackle with them have been revealed by Seiler (1983, 1987, 2001), Seiler & Lindner (1995). They have shown that, once the passive recharge zone of a groundwater system is penetrated by pumping wells and the duration and/or rate at which these are operated exceeds a certain threshold, the natural hydrogeologic barrier between the passive and the active recharge zone gets disrupted, and deep water turnover rates get visibly accelerated; alongside with them, the migration of near-subsurface pollutants towards greater aquifer depths is enhanced in such a way that (a) it remains unnoticeable to standard water quality monitoring for a good number of years, and (b) by the time it is perceived by standard monitoring instruments, it has already affected depths and areas so large that it has turned into a major, irreversible degradation of water quality at regional scale. The deep water abstraction rate beyond which such negative effects occur lies far below the bulk recharge rate estimation; moreover, the actual 'feeding streamlines' of a deep pumping well stretch laterally far upstream the well, so that the usual protection zones concentric around the well itself will not really protect it (Seiler 1987, 2001). Here, the possibility of an early-warning system regarding deep aquifer contamination, and of a process-oriented control of deep groundwater abstractions is examined anew: first explained in terms of a time scale contrast between the transport of 'polluting' and of 'monitoring' species, it is then investigated numerically for two hydrogeologic situations, one with a mild and one with a marked permeability change over depth. The progressive contamination of the deep aquifer is simulated assuming a simplified, yet realistic scenario of shallow aquifer pollution; and the environmental radioisotope response to deep water abstractions is predicted as a function of pumping rate, duration and depth, and of aquifer heterogeneity. The readjustment time of environmental radioisotope repartitions under given hydraulic stress lies somewhere between the (relatively short) pressure adjustment time (determined by hydraulic diffusivities, or T/S) and the (depth-dependent) groundwater age value. The time scope of radioisotope response to hydraulic stress will thus increase with depth, however in competition with radioactive decay which makes isotope concentrations decrease with depth and become irrelevant below a so-called 'nil-line' defined by the detection limit of the respective isotope (the latter may advance toward greater depths, as detection techniques improve). The possibility of an EARLY-WARNING system resides in the time-scale contrast between the ('slow') migration of polluting species and the ('rapid') spatial readjustment of monitoring species. The time scope of a PROCESS-ORIENTED control is confined to the interval in which the response of monitoring species correlates monotonously with the magnitude of the applied stress (pumping rate). For deep porous aquifers of the (Bavarian) Upper Freshwater Molasse with an average porosity over 10%, the time scope of a process-oriented control, before the environmental radioisotope responses under different pumping regimes approach a common plateau, comprises at least 4-5 decades. Besides hydraulics and solute transport, an interest arose for dealing with transient groundwater ages, during or following hydraulic stress. Groundwater age, or 'flow-time', or residence time repartitions are often invoked as a 'microscopic' foundation of lumped-parameter models for (conservative) solute transport in groundwater. How stable are these repartitions against hydraulic perturbations? can their hydraulically-induced shift with time be related consistently and unequivocally to variations in the lumped-parameter values used by black-box models to assess system change? Part of the answer is provided by groundwater age - hydraulic head phase portraits, which are marked by hysterese. The direct, unsteady age modeling furthermore reveals the possibility of a 'groundwater age mining' to occur even without having a 'groundwater mining'.