Surplus moneys in the drinking water loan account established by section 39-7602, Idaho Code, shall be invested by the state treasurer in the manner for idle state moneys in the state treasury as provided for in section 67-1210, Idaho Code. Interest received on all such investments shall be paid into the account. The account shall have paid into it: federal funds which are received by the state to provide for drinking water loans to public water systems together with the required state matching funds; all principal and interest repayments of loans made pursuant to this chapter; all donations and grants from any source which may be used for the provisions of this chapter; fund transfers from the wastewater facility loan account; and any moneys which may hereafter be provided by law.