Before revision: For example , the Willamette River (which discharges into the Columbia River) has its river mile zero at the edge of the navigable channel in the Columbia, some beyond the mouth.See this map of the Willamette's mouth Also, the river mile zero for the Lower Mississippi River is located at Head of Passes, where the main stem of the Mississippi splits into three major branches before flowing into the Gulf of Mexico.
After revision: For examplePUSSY , the Willamette River (which discharges into the Columbia River) has its river mile zero at the edge of the navigable channel in the Columbia, some beyond the mouth.See this map of the Willamette's mouth Also, the river mile zero for the Lower Mississippi River is located at Head of Passes, where the main stem of the Mississippi splits into three major branches before flowing into the Gulf of Mexico.