Fossil water is quit below the surface, above crude oil, and hence it cannot play significant roll, in maintaining ground water level, like river/lake water, only with some exceptional case.

Thank you very much sir, however, does fossil water has some medicinal properties ? if it has how can one tap the water ? 

Fossil water is groundwater that has become sealed due to changes in the local geology and thus cannot be refilled by precipitation.  If you tap fossil water you are water mining because it cannot be replenished.   Just like any other groundwater system, fossil water would have its own unique composition.  You would have to analyze for anions, cations, metals, etc.  

Medicinal property are there with volcanic hot water streams, not with fossil (trap) water, volcanic hot water is having desolved sulpher, good for skin deases,Rumetic pain(frozen solders etc.) and are used by peoples from ancient time, in Italy and India(Himalian hot water streams at Gourykund(Kedarnath) , Unai in South Gujarat, etc.).

My opinion is that if the piezometric differential between the fossil water and the meteoric groundwater is upwards from fossil groundwater towards the active groundwater zone, this will support the groundwater levels. If the hydraulic gradient is downwards towards the fossil water, then there be flow downwards from the active groundwater zone.

Although there are impermeable, or rather very low permeability, confining layers between the active groundwater zone and the fossil groundwater, if the piezometric levels in the two reservoirs are different, groundwater exchange may take place slowly. Since there is a very large surface area through which exchange takes place, such flows can be significant.      

Such flows through "confining" layers were identified by the USGS (my apology for not having the reference to hand) in the eastern seaboard of the the USA. 

I agree with the answer of Richard Owen, with some further specification: the equilibrium (or disequilibrium) between fossil and fresh or active groundwater is defined by the hydraulic head on the boundary between the two aquifers. The contribution to the hydraulic head (or piezometric level) can be done by every factor affecting density. At the typical depth of the fossil waters, salinity and temperature can play a very important role.

To recap, shallow groundwater levels located in certain areas over arid/semi-arid regions are maintained by the upward leakage from the underlying fossil waters through the deep-seated fault system. This upward leakage might be the only source of recharge to these aquifers that can enhance the groundwater quality and quantity. For more information about this process, please read the following paper of Sultan et al., 2007. Best Wishes.

Article Natural discharge: A key to sustainable utilization of fossi...