Map of the Olentangy Watershed 

Currently, the Olentangy River flows 88.5 miles from its headwaters in the Crawford and Richland Counties through Marion and Morrow counties into Delaware. The river above the Delaware Dam is considered the upper portion and below the dam is considered the lower. The Olentangy ends in the Franklin county at the confluence with the Scioto River in downtown Columbus. In all, the river has a drainage area of 543 square miles.