Sec. 3. (a) The fund consists of the following:
(1) All revenues accruing to the department from the operation of the state parks.
(2) All revenues accruing to the department from the operation of reservoirs.
(3) Other sources as specified by law.
(b) The treasurer of state shall invest the money in the fund not currently needed to meet the obligations of the fund in the same manner as other public money may be invested.