Except where specific provisions of an enterprise fund or other special purpose fund set forth different requirements, or the fund is otherwise restricted by law or contractual agreement, the following shall be applicable: The source of anticipated revenues shall be identified as part of the annual budget and estimated revenues and expenditures therein described. At the end of each fiscal year, unexpended funds shall not automatically lapse into the general fund but shall accumulate within the fund and be available for appropriation to the fund in subsequent fiscal years.