Projections of water shortages have halted development on the fringes of the Phoenix metro area. And Arizona Senate President Warren Petersen, who is also a real estate broker, is no fan of a regulation at the heart of those projected shortages, a requirement for residential developers in urban areas to show they have a 100-year-water supply. “You have to have a 100-year water certificate for your house. Why wasn’t it 105 years? Why wasn’t it 95 years? Do you know what the highest water supply requirement in the nation is outside of Arizona? It’s California. And it’s 25 years,” Petersen said. But Sarah Porter with the Kyl Center for Water Policy at Arizona State University says there’s a good reason the 100-year requirement was included in Arizona’s 1980 Groundwater Management Act.