California Code, Streets and Highways Code - SHC § 25346

The board of supervisors of each county shall, within 90 days after the resolution providing for the levy has been adopted by the board of directors, pay at least one-fifth of the total amount levied upon that county into the treasury of the district.  The board of supervisors of each county is hereby authorized to and obligated to make such payment and may make payment of the entire amount of the levy made but not less than one-fifth of the total thereof.  For the purpose of making the payment the board of supervisors of each county may utilize any funds of the county not otherwise allocated or appropriated, including any money received by the county from the State as the result of any tax or license upon motor vehicles or motor vehicle fuels.