With California in its fourth successive year of drought, the water usage restrictions announced earlier this month by Gov. Edmund G. Brown, Jr. seemed inevitable. Much, however, depends on whether the state’s residents will fall in step to curb excessive water use and help redirect the scarce resource to human health and safety, growing food and fighting forest fires. “Social norms are difficult when you can’t see anyone,” said Howard Kunreuther , Wharton professor of operations and information management. “The idea of people taking a shower that is only five minutes would be very hard to monitor and control.” Kunreuther is also co-director of Wharton’s Risk Management and Decision Processes Center . Kunreuther spoke about the challenges California faces in winnings its war on drought on the Knowledge at Wharton show on Wharton Business Radio on SiriusXM channel 111 . (Listen to the podcast at the top of this page.) “Social norms are difficult when you can’t see anyone.…