Mich. Comp. Laws § 280.445

Sec. 445. The merging of any drainage district into a consolidated district shall not affect the obligation of any bonds issued or contracts entered into by such district nor invalidate the levy, extension or collection of any taxes or special assessments upon property in the debtor district, but such bonds and contracts shall be taken over and assumed by the consolidated district, and all outstanding special assessments shall be collected and paid over to the consolidated district for the payment of the obligations theretofore issued or contracts entered into by the debtor district.