One or more improvement districts may be formed in the Kings County Water District which may include all or any part of the land in the district in the manner prescribed in Chapter 5 (commencing with Section 31585) of this part for capital outlay purposes, including, but not limited to, the acquisition of stock of mutual water companies. If any such improvement district is formed pursuant to this section, assessments shall be levied, collected, and enforced exclusively upon land within such improvement district to raise the funds necessary for the purposes of such improvement district. Such assessments shall be levied, collected, and enforced at the same time and as nearly as may be practicable as annual taxes for the purposes of the district. If bonds are to be issued on behalf of any such improvement district pursuant to Section 31610, the board may, in determining the amount of debt to be incurred, include the estimated cost of all stock of mutual water companies which the board determines should be acquired by such improvement district, even though all of such stock is not then available to be so acquired.