Groundwater is nonrenewable

"The water that supplies aquifers and wells that billions of people rely on around the world is mostly a non-renewable resource that could run out, a new Canadian-led study has found.
While many people may think groundwater is replenished by rain and melting snow the way lakes and rivers are, underground water is actually renewed much more slowly.
In fact, just six per cent of the groundwater around the world is replenished within a "human lifetime" of 50 years, reports University of Victoria hydrogeologist Tom Gleeson and his collaborators in a new study published in the journal Nature Geoscience today."

Well crap. That's news to me. And it is very, very bad for the future. Lots of countries rely on groundwater to grow crops.