Yes. We are mining water. While notionally replenishable, we are withdrawing from the water table in many areas (I'm familiar with California) so much faster than the replenishment rate that the aquifer is collapsing, meaning it will never be able to hold the water it used to anymore.

Yes. But it depends on the aquifer. For example the Edwards Aquifer in Texas gets recharged from rainfall. But the Ogallala Aquifer supplies water at least 10,000 years old and rain doesn't affect it. Once we pump the Ogallala dry it will stay dry.

We pump it up by the megatonne over decades, we spray it outwards for crops or to water animals.

Some travels back down through the soil, most either evaporates or is taken up by plant matter, sweat out, goes to meat, etc. - which results in movement of the water mass to elsewhere on the planet.

Groundwater reservoirs have a recharge rate. That is the rate that surface, or I suppose even deeper, water is sequestered in the layer in question. We are extracting faster than that recharge rate.

I have no idea, but:

Groundwater naturally is somewhat steady state. You get rain, it filters through and then there is spring or something somewhere and goes back to cycle in river or evaporation. Part of the cycle.

Now if you remove more water than exit through the natural processes you move it out from groundwater table. Thus creating imbalance and changing the steady state.

There are many ways to recharge the ground water. One is filling up dedicated basins periodically and letting the water trickle down. These basins are managed regularly to allow the water to percolate. Rivers also help with ground water recharge but only within their watersheds and routes. Also, Newsom in California recently issued an executive order to use flood water from recent rains for ground water recharge. https://www.gov.ca.gov/wp-content/uploads/2023/03/Refilling-...

Mining and trapping groundwater in billions of tonnes in sugary soft drinks which then sits in supermarkets maybe?