Water began flowing from a pipe onto hundreds of acres of dry, sunbaked lake bed as California officials filled a complex of shallow ponds near the south shore of the Salton Sea in an effort to create wetlands that will provide habitat for fish and birds, and help control lung-damaging dust around the shrinking lake. The project represents the state’s largest effort to date to address the environmental problems plaguing the Salton Sea, which has been steadily retreating and leaving growing stretches of dusty lake bottom exposed to the desert winds.