All income derived from the sale, delivery and distribution of electrical energy, shall be deposited with the county treasurer of the county in which the office of the board of directors of the district is located, and shall be apportioned to such fund or funds of the district authorized by law, as the board of directors shall deem advisable, including, but not limited to the payment of district bonds or any portion of the same for which such revenues have been pledged and thereafter said income, or such portion thereof so pledged, shall be placed by the county treasurer to the credit of the fund from which said bonds are required to be paid until the same or the portion thereof secured by such pledge are fully paid.