Moneys received under the provisions of title 19 of this article shall constitute a fund to be known as the drainage improvement district fund, and the portion thereof applicable to each improvement shall be separately kept by the Comptroller, and the Comptroller is authorized and directed to pay therefrom the principal and interest of such obligations as the same mature and become payable by the terms thereof, and the costs and expenses of such improvement and the maintenance thereof upon the order of the department or the authorized officer thereof.