The assessor must be bonded in the amount of five hundred dollars, and the district treasurer must be bonded in an amount not less than double the amount of money that may come into the treasurer’s hands, the amount to be determined by the board of directors but not be less than one thousand dollars. Other employees and appointed officers must be bonded in amounts prescribed by the board. The official bonds of the assessor, treasurer, and other officers and employees must be approved by the board and filed in the office of the department of water resources.