That's because the Hsiukuluan empties out into the sea at different places depending upon the season. The mouth of the Hsiukuluan River is divided into northern and southern exit points by Hsipulan Island (aka Shihchiu Island).
原來秀姑巒溪在不同季節，出海口也不同。秀姑巒溪口因奚卜蘭島（又名獅球嶼）之隔，分為南北兩個出海口。