The council shall adopt a capital budget prior to the beginning of the fiscal year in which the budget is to take effect. No appropriations for a capital improvement project contained in the capital budget shall lapse until the purpose for which the appropriation was made shall have been accomplished or abandoned, provided that any project shall be deemed to have been abandoned if three fiscal years lapse without any expenditure therefor. Any such lapsed appropriation shall be applied to the payment of any indebtedness incurred in financing the project or if there is no such indebtedness, shall be available for other appropriation. The council may by ordinance establish a reserve fund for permanent public improvements and may appropriate thereto any portion of the general fund cash surplus not otherwise appropriated. Appropriations from said fund shall be made only to finance improvements included in the capital budget.