The Pleides (Arabic: البلادي al-balādī) is the longest river in the Sinai. Originating from a vast network of wadis supplied by flash-flood charged ephemeral streams in the central and southern highlands of the peninsula, the river begins as a series of tributary streams before joining into the recognizable river about 25 kilometres south of Bir Hassanah. The river then bends around Bir Hassaneh's north edge (where underground tributaries to the Pleides feed the city's namesake well) to Caeffa, flowing eastward then northeastward to zig-zag through Ibrahimia. Finally, the river empties into the Mediterranean 15 kilometres to the north at Arish.
Due to the nature of the river's origins, namely flash floods which fill otherwise dry tributaries during spells of rain, the Pleides varies between a mightily flowing river and a parched, barely trickling stream depending on the season.