The natural resources equipment fund shall be reimbursed by the department for all moneys expended from it. Reimbursement may be prorated over the useful life of the equipment, machinery, and supplies purchased by moneys from the fund. Reimbursement may be made from moneys appropriated or otherwise available to the department for the purchase, repair, and maintenance of equipment, machinery, and supplies and shall be prorated on the basis of relative benefit to the programs. For the purpose of making reimbursement, all existing and hereafter acquired equipment, machinery, and supplies of the department shall be deemed to have been purchased from the natural resources equipment fund.