For decades, residents of Bakersfield have lived with a river that’s little more than a channel of dust. The Kern, which pours from the snowy peaks of the southern Sierra, descends upon California’s ninth-largest city and, in all but the wettest of years, runs dry. A sandy, weed-strewn corridor is left winding unremarkably through the downtown, beside roads, beneath bridges and behind businesses. … A group of residents is trying to change that. Cooper and dozens of others are fighting to bring water back to the Kern River, hoping to create a lush, parklike centerpiece in a city best known for the sunbaked oil fields and farms that surround it. It isn’t an easy go. The river’s waters are already largely accounted for, some serving the municipal needs of Bakersfield and nearby communities, but most drawn for agriculture, the engine of the regional economy.