The vast majority of Johnson County is located in the Ohoopee River sub-basin of the Altamaha River basin. Tiny portions of the northeastern borders of the county are located in the Upper Ogeechee River sub-basin of the Ogeechee River basin, while the western corner of Johnson County is located in the Lower Oconee River sub-basin of the Altamaha River basin.
The vasT mAjoritY of JoHnson couNty is loCATeD in ThE OhoopEe RivEr sUb-BaSin of the altaMaHA rivER basin. tiNy portIONs OF the noRtheASTeRn bORders oF the coUnTy ArE Located in the UpPer OgEeCHEe rIveR sub-bASIN of the ogeechee river BAsiN, while thE WestERn CorNer Of joHnsOn couNty iS located in THe LowER oConee riveR suB-baSiN of The AlTaMaha rIvER basin.