SIERRA VISTA — The southern portion of Arizona may be the anchor of an emerging megapolitan area in which the population in the Sierra Vista Subwatershed could double by 2050 to more than 110,000 people. All of Arizona is rapidly growing and major development is along major highway corridors from the north in the Prescott area to southern Arizona, which includes Sierra Vista and a large portion of the western part of Cochise County, said Robert Lang, an expert on urban planning issues. Officials and environmentalists say actions must be taken to ensure that growth is logically accomplished, taking into...