California has some of the world's most productive agricultural land. It puts fruit and vegetables on America's tables and exports huge amount of produce too; nearly all of the almonds we consume come from there. But the state is also enduring a severe drought, now into its fourth year. Farm land is being fallowed, farm workers are losing their jobs and thousands of wells are drying up. Some farmers believe that this year is the tipping point. If rain does not fall in the winter, they'll be unable to farm next year. But others have had some of their best years during these testing times. Peter Day explores what happens when water becomes the most valuable commodity there is.

Producer: Rosamund Jones