(沿河流)上溯

1. to go upstream, to go up (a river)

Godan verb with 'ru' ending intransitive verb word usually written using kana alone

回溯(历史等)

2. to go back (to the past or origin), to date back (to), to trace back (to), to be retroactive (to)

Godan verb with 'ru' ending intransitive verb word usually written using kana alone