A. Fund Established; Disbursement: There is hereby established a water system improvement fund to be maintained by the city clerk in managing the fiscal affairs of the city. All revenues derived from the charging of any fees, charges, or rates, as such are set forth herein shall be deposited in said fund and shall be disbursed only for the purposes of maintaining, repairing, studying, controlling, enlarging, extending, enhancing, or improving the water system of the city. (1980 Code § 4.6.23)