Part of the river towards the upstream direction.
"The fisherman cast his line into the deeper part of the river that lies further upstream."
In plain English: Upstream is water that flows toward its source, away from where it empties into an ocean or lake.
"The fisherman waited at upstream to catch more trout before they moved downstream."
To stream upward.
"The fish swam upstream against the strong current to reach its spawning grounds."
in the direction against a stream's current
"The boat moved upstream to reach the source of the river before sunset."
in a direction against the flow of a current or stream of fluid (typically water); upriver
"The fish swam upstream to reach its spawning grounds before the river flooded."
In plain English: Upstream describes something that is located higher up and closer to where water begins its flow, rather than lower down toward the ocean or sea.
"The water in our upstream river was very clear after the rain stopped."
Usage: Use "upstream" to describe anything moving toward the source of a flowing liquid, such as traveling against a river's current. In technical contexts like computing, it refers to data or processes originating from an earlier stage in a chain rather than those following later stages.
Against the current.
"The fish swam upstream against the strong river current."
The word upstream is formed by combining the prefix up- with stream. It literally means located or flowing toward the source of a river.