Something that is moving upstream is moving towards the source of a river, from a point further down the river. Something that is upstream is towards the source of a river.
例句
The water rose high enough for them to continue upstream.水位漲得夠高了，他們可以繼續向上游航行。...the river police, whose headquarters are just upstream of the Isle St Louis...總部設在圣路易島上游的水警
英漢詞典釋義
adv.
向上游(的);逆流(的)
The ice blocks up the river, making the upstream water unable to flow.冰把河道堵住了, 上游的水流不下來。We swam upstream against the current.我們逆流向上游游去。