hamby is vice president of the board that runs california's imperial irrigation district, one of thehest agricultural regions in the country, with the single largest allocation of water on the entire river. >> hamby: there's a lot of urban growth and sprawl occurring in other parts of the colorado river basin that's really not necessarily sustainable. >> whitaker: hamby says california's imperial valley farms have cut water usage almost 20% since 2003, but points out as the population of st. george, utah grows, so does its water use. >> hamby: we need to think and rethink about how we grow, and if we grow and where we grow. >> whitaker: st. george would say that they're not asking for more-- they're asking for what they need. >> hamby: i think what we all need to have is a reality check, here, and recognize that we live in an era of limits right now, and that's not going away anytime soon. in fact, it's only going to get worse. >> whitaker: a big part of the problem is the law of the river itself, a hodgepodge of rules and regulations pieced together over the course of a century. for