Unless otherwise provided by law and except for grant appropriations or grant funds deposited in special accounts dedicated to specific functions, activities or purposes, all unexpended and unencumbered appropriations in the Operating Budget at the end of the fiscal year shall revert into the treasury. No appropriation for a Capital Project in the Capital Budget may revert until the purpose for which the appropriation was made is accomplished or abandoned; but any Capital Project shall be considered abandoned if three fiscal years elapse without any expenditure from or encumbrance of the appropriation.