Upstream means against the flow of a river. Swim upstream, upstream of the bridge, walk upstream.
It is harder work and it is where the cleaner water is, which is why settlements and intakes are placed there. Figuratively, upstream means earlier in a process — fixing a problem upstream stops it appearing downstream — and in the oil industry upstream is extraction. Note downstream, its opposite.
1adverbupstreamAgainst the flow of a river.
“Salmon swim upstream every autumn to lay their eggs.”
2adjectiveearlierEarlier in a process.
“The delay was caused by an upstream supplier who sent the parts late.”
upstream is a direction.
Proto-Indo-European
*srew-
Middle English
strem
English
stream
English, today
upstream
From up- + stream. stream comes from Middle English strem. From Middle English streem, strem, from Old English strēam, from Proto-West Germanic straum, from Proto-Germanic straumaz (“stream”), from Proto-Indo-European srowmos (“river”), from Proto-Indo-European srew- (“to flow”). a doublet of rheum. Cognate with Scots strem, streme, streym (“stream, river”), frr Stroom, struum (“stream”), West Frisian stream (“stream”), Low German Stroom (“stream”), Dutch stroom (“current, flow, stream”), German Strom (“current, stream”), Danish and Norwegian Bokmål strøm (“current, stream, flow”), Norwegian Nynorsk straum (“current, stream, flow”), Swedish ström (“current, stream, flow”), Faroese streymur (“stream”), Icelandic straumur (“current, stream, torrent, flood”), Ancient Greek ῥεῦμα (“stream, flow”), Lithuanian srovė (“current, stream”) Polish strumień (“stream”), Welsh ffrwd (“stream, current”), Scottish Gaelic sruth (“stream”).
Etymology from Wiktionary, CC BY-SA