A water shortage warning has been issued to 8.1 million residents from Orlando to the Florida Keys. South Florida Water Management District Board Chairman Dan O’Keefe said that residents’ voluntary efforts will help the water supply last through the region’s dry season. If those efforts prove insufficient, mandatory water restrictions may be considered. Drought conditions have prompted the district to prohibit fires on its lands and prepare to close navigation locks on Lake Okeechobee’s north shore. Officials said rainfall across the district’s 16 counties since Nov. 1 has been 6.75 inches below average. Water levels in Lake Okeechobee have dropped to 12.04 feet.