According to the Yoshufushi (gazetteer of Yamashiro Province), the river downstream to the south of Saga was named the Katsura-gawa River since the 'Katsura-no-sato' (village of Katsura) lay on the west side of the river, while upstream, to the north of Saga around Arashiyama, the river was described as the Oi-gawa River.
「雍州府志」では、川の西に桂の里が有ることから嵯峨より南の下流域を桂川と呼ぶようになったとあり、それより上流にあたる嵐山流域をやはり大井川としている。