If anyone is talking to a wingnut who claims the California drought is a man-made political problem because of the May 2007 court decision to redirect water to the Delta in order to save the Delta smelt, I have a couple of figures that might help.

Since May of 2007, the redirection of water has reduced the amount available for irrigation in the San Joaquin Valley area by ~3,300,000 acre ft. However the drought has removed ~13,333,330 acre ft of water from the same area. That doesn’t include water lost by evaporation.

The drought is measurably the result of a reduction in rainfall, not the redirection of water. The redirection is adding to the problem but it certainly isn’t the reason farmers are suffering. Adding that water back into the irrigation system wouldn’t help the majority of farmers, but a normal rainfall would help them all.

Just as a side note - the Delta suffers an incursion of salt water when the water level drops and that affects the viability of surrounding farmland. Adding water to the Delta not only saves the Delta smelt but reduces the salt content of surrounding areas.