Aquifers have a natural recharge rate. However, some aquifers rely on fossil water for their primary (or even sole) water supply. When water in a well is pulled from these aquifers faster than they can replenish, the level drops and they eventually "dry up" (or the water table drops below the bottom of the well, at least). In the case of aquifers with no recharge, such as fossil water, it seems that the water could literally be used up so that the aquifer becomes completely dry.

For these fossil water aquifers, is there any known technique to recharge them? Since they're labelled as a non-renewable resource, I presume the answer is "no", but I'd like to get a better understanding of this.

For aquifers with a low recharge rate and a severly dropped water table, is there any known way to increase their recharge rate?

  • $\begingroup$ I'm pretty sure the answer is "no", but I'd just like verification. $\endgroup$
    – Richard
    May 2 '14 at 14:42
  • $\begingroup$ The sentence "Aquifers have a natural recharge rate" makes it sounds like its a natural constant. I would edit that out, especially because your question is about aquifers that don't recharge. $\endgroup$ May 2 '14 at 20:27
  • $\begingroup$ Over what timescales? A lot of "fossil water" is in aquifers that just have recharge rates of a few thousand years. Short geologically, long on human timescales. There's the separate issue of porosity loss due to compaction, though. $\endgroup$ May 3 '14 at 2:11

Fossil groundwater is water that has been trapped below the surface for several thousands of years. It is considered non-renewable as natural recharge on human timescales is practically zero. This is because the permeability/transmissivity of the overlying strata is very low.

However, on geological timescales the aquifer will recharge as pumping the water out of the aquifer decreases the hydraulic head, and therefore increases the gradient over the aquitards sealing the aquifer. Therefore the recharge of the aquifer actually speeds up by withdrawing water, although probably not in amounts humans can profit from.

Since you're asking about techniques to recharge, techniques similar to those used for shallower aquifers could be applied. In the Netherlands regeneration of groundwater is performed to decrease the stationary drawdown of the groundwater by the pumping which leads to damages for farmers. This is often performed by pumping surface water into the aquifer at some distance so the aquifer is recharges artificially and the groundwater table rises.

On the other hand, recharge of these fossil water aquifers in arid areas such as the subtropics is probably infeasible, even though it would be technically possible.

  • 2
    $\begingroup$ The practice of storage and recovery of surface water in the carbonate Floridan aquifer has actually led to the mobilization of arsenic in some areas. The point here is that mixing waters with significantly different chemical properties can have unintended consequences. water.usgs.gov/ogw/pubs/ofr0289/jda_mobilization.htm $\endgroup$ Dec 29 '14 at 15:39

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