(A) Supplemental appropriation. If no provision in the appropriation is made for the municipality to conduct the indispensable functions of government, the governing body may approve and adopt a supplement appropriation ordinance, provided that it sets out in detail the reason and amount for each appropriation. The procedures to adopt the supplemental appropriation are the same as for the annual appropriation ordinance.
(SDCL § 9-21-7)
(B) Emergency appropriation. If an event occurs that could not have been reasonably anticipated at the time the annual appropriation was created and adopted, the governing body may order the mayor or president to borrow, in the name of the municipality and with the attest of the finance officer, a amount sufficient to provide for the necessary expense incurred by the emergency event.
(SDCL § 9-21-15)