Recovery scenarios for deep over-exploited aquifers with limited recharge: methodology and application to an aquifer in Belgium |
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Authors: | M Van Camp K Walraevens |
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Institution: | (1) Laboratory for Applied Geology and Hydrogeology, Ghent University, Krijgslaan 281 S8, 9000 Ghent, Belgium |
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Abstract: | Recharge of deep-seated aquifers must be provided through leakage from overlying geological formations and can be very limited.
Although hydraulic characteristics of these aquifers may be favorable for extensive exploitation, the renewability of the
groundwater resource may be very restricted and only significant on long time scales. Over-exploitation of such aquifers leads
to steadily declining piezometric levels and water balancing and steady state conditions are not to be expected on the short
term. Recovery of such systems is very difficult, also because of the socio-economic dependencies of the water resource and
the long time it requires to replenish the system. Management plans for restoration should be based on the transient hydrodynamical
behaviour. A recovery plan should be developed based on results of a groundwater flow model. In a first step must be simulated
how long it will take for the aquifer system to fully recover by natural recharge. As this will most often be a very long
time it can be cancelled out as a realistic scenario. An alternative objective is to be formulated which could be achieved
in the near future on a time scale of years or decades. Using model simulations, reduction schemes of exploitation rates shall
be quantified that will allow to reach these defined goals, such as raising piezometric levels above the top of the aquifer
itself or above the top of the overlying geological unit. The methodology is illustrated with an example of a deep hard rock
aquifer in Belgium where piezometric levels have dropped below the top. The objective here was to raise the levels again above
the top within the next 50 years. However, this is not accomplished by balancing aquifer recharge and discharge, but is reached
by a lateral redistribution of the water over the aquifer extent. A full recovery of this aquifer would require at least a
century with only a very limited amount of exploitation. |
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Keywords: | Over-exploitation Flow model Belgium Recovery |
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