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As a number of folks have commented when water is removed too quickly from the aquifer it subsides and can't be refilled by percolation.

In a sad, and very close to home, way Sunnyvale has been drawing more heavily on wells in the area to back fill water allocations and that appears to have created some subsidence near my home.

But from a technical point of view, one wonders if it would be possible to build replacement aquifers underground. I'm imagining something related to a tunnel boring machine but leaves behind a structure capable of holding water and supporting the ground above itself when "empty" sort of a loose lattice network of structures.



It might be possible, but I don't think it would be practical. It's easy to forget how big the numbers are when dealing with water.

For example, all three Chunnel tunnels add up to less than 4500 acre-feet in volume.


The relationship between subsidence and groundwater pumping was actually discovered in the Santa Clara Valley in the 1940s. As a result, percolation ponds were built in the 1960s to recharge local aquifers and ground water pumping by the Santa Clara Water District (which serves Sunnyvale) was reduced to sustainable levels. Subsidence basically stopped in 1969. If it has returned, that would be a sad development.


I remember reading about Sun Valley in LA County that built cisterns to regulate flooding and then use that water for irrigation during dry periods.




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