Mich. Comp. Laws § 121.20

Sec. 20. The legislative body of each city, village or township which is a part of the authority may raise by tax, pay from its general funds, or from its revenues derived from operation of its water system not earmarked or pledged for other purposes, any moneys required to be paid for water purchased from the authority by the terms of any contract between it and the authority pursuant to the provisions of section 10 of this act.