I'm standing on the bridge on the Waterford County side. At about the midpoint of the bridge it changes to County Cork.

The Blackwater or Munster Blackwater (Irish: An Uisce Dubh, The Black Water) is a river which flows through counties Kerry, Cork, and Waterford...It rises in the Mullaghareirk Mountains in County Kerry and then flows in an easterly direction through County Cork, through Mallow and Fermoy. It then enters County Waterford where it flows through Lismore, before abruptly turning south at Cappoquin, and finally draining into the Celtic Sea at Youghal Harbour. Wikipedia