Here’s the progression of innovation in irrigation technology from spray, to low energy precision application, to drip irrigation to subsurface drip irrigation.  The question we’re asking in arid Saudi Arabia is can we use the sun to power enough desalination to support enough desalination to grow crops in the desert.  Saudi Arabia’s problems aren’t much different from those of our arid southwest.  In many places, agriculture is living on borrowed time:  Saudi Arabia’s aquifers and our huge Ogallala aquifer are being drained  -- and are not being recharged – that’s the definition of a fossil aquifer.