Something that is moving ~ is moving towards the source of a river, from a point further down the river. Something that is ~ is towards the source of a river.
The water rose high enough for them to continue ~.
...the river police, whose headquarters are just ~ of the Isle St Louis...
? downstream
ADV: ADV after v, be ADV, n ADV, oft ADV of/from n
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Upstream is also an adjective.
Steps lead down to the subway from the ~ side.
? downstream
ADJ: ADJ n