No moneys shall be drawn from the Treasury of the City, nor shall any obligation for the expenditure of money be incurred, except pursuant to appropriations made by the Council; and whenever an appropriation is so made the Clerk shall forthwith give notice to the Auditor. At the end of each year all unexpended balances of appropriations shall revert to the respective funds from which the same were appropriated and shall then be subject to future appropriations; but appropriations may be made in furtherance of improvements or other objects or work of the City which will not be completed within the current year.