By Reem Shamseddine and Barbara Lewis KHOBAR/LONDON (Reuters) - Long before it understood the value of oil, the desert kingdom of Saudi Arabia knew the worth of water. But the leading oil exporter's water challenges are growing as energy-intensive desalination erodes oil revenues while peak water looms more ominously than peak oil -- the theory that supplies are at or near their limit, with nowhere to go but down. Read More...