Linked here, is a really interesting article sent to us by an investor in the Global Water Fund. Unknown to to us, Saudi Arabia was once the worlds sixth largest exporter of wheat, a crop made possible entirely by water accessed from a massive aquifer below the desert country. But intense usage has drained that aquifer in less than 30 years, it will take tens of thousands of years to replenish. The Saudi government has just announced that next years wheat harvest will be its last due to lack of water. The country now has less than half the farmland as it had in the 1990's.
The same process is happening in California, starting a cascading process where water depletion in one country leads to reduced agricultural output, which leads to increased demand for imports from another country, which leads to over production and water depletion in that country, and so on.