Great question.

I suspect that if the water table is high enough to cause problems, you'd do pumped hydro storage instead.

A lot of solar power is out in the desert where the water table is hundreds or even thousands of feet below surface.

But we're talking about energy storage close to consumers, not in remote locations I thought? For deployment in Europe, I don't think it'd be possible to find areas where ground water is that deep (luckily).

And pumped storage still doesn't work as you'd need surface area for new lakes. Also, not sure if you'd want to pump out huge amounts of ground water for pumped storage, lowering the water table for everyone.

My civil engineer partner could speak to this in more detail, but it's a well-understood solvable problem. You seal the shaft wall as you dig past the water table. And some small amount of pumping is used as needed.