The two southern feeder Hydro reserves start from the slopes of Mount Sedgwick, the westerly from Lake Barnables (less than east of Lake Margaret), then to Lake Phillip. The eastern feeder starts at an unnamed lake to Lake Polycarp, Lake Peter, Lake Paul, Lake Apollos, and then to Lake Phillip. The northern feeder starts from Lake Monica, Lake Myra, then Lake Magdala, situated at , Lake Martha, at , and Lake Mary, at , before flowing into Lake Margaret.