Current (hydrology)

The current varies spatially as well as temporally, dependent upon the flow volume of water, stream gradient, and channel geometry.

In tidal zones, the current and streams may reverse on the flood tide before resuming on the ebb tide.

On a global scale, wind and the rotation of the earth greatly influence the flow of ocean currents.

[1] In a stream or river there the current is influenced by gravity, the term upstream (or upriver) refers to the direction towards the source of the stream (or river), i.e. against the direction of flow.

Likewise, the term downstream or downriver describes the direction towards the mouth of the stream or river, in which the current flows.