The salaries or wages of all officers and employees of a district shall be paid periodically as the board may prescribe. At the expiration of the period fixed for the payment of salaries or wages a payroll shall be prepared, showing all persons employed during the preceding salary period and stating the amount of compensation to which each person is entitled. Payment of the salary or wages of each person specified in the payroll may be made after approval of the payroll by the board or the general manager in accordance with rules adopted by the board.