Since the early 1990s, South Lee’s sprawling suburbs stayed left of an invisible county firewall known locally as the DRGR, which stands for Density Reduction Groundwater Resource area. Lee created the DRGR, in part, to protect the county’s drinking water supply. But as Lee’s population creeps toward more than 1 million residents by 2040, county officials are contemplating a shift in the way they control growth and conservation in rural southeastern Lee.