The California Department of Water Resources underwent a management shakeup Wednesday, less than a week after investigators released a scathing report on last February’s crisis at Oroville Dam and how the department handled it. Grant Davis resigned as DWR’s director barely seven months after taking over the embattled department, which has been heavily criticized following the near-catastrophe at the dam’s two flood-control spillways. Davis will go back to his old job as general manager of the Sonoma County Water Agency.