If your following the Japan Earthquake news , officials are sending helicopters to pour water over radioactive reactors that had blown up because of a threat it poses - contamination of the world's water table.

A water table is essentially... Well , groundwater basically and groundwater is actually one of the few things humans can expect to find clean water of.
Basically , the high temperatures and what not of the blown reactors and the radioactive substances are seeping into the soil so... Well , now you at least have an idea of the situation.

This doesn't solely concern Japan anymore , this will seriously affect the Earth's water supply to a certain extent :X
Things are starting to sound just a bit grim....