Sump pump discharge is typically a private matter between you and your neighbor. However, the City of Ankeny's Code Enforcement Officer will investigate and talk to your neighbor.
Sump pumps should be plumbed to discharge to a storm sewer system (not the sanitary sewer).
If no storm sewer is available, sump pumps should discharge above ground, within the property boundary. There are other possible discharge methods, but above-ground and to storm sewers are the most common.