"Downstream" and "upstream" can mean different things. They can be either adjectives or adverbs, and refer to either directions or relative positions.
Refering to directions, I believe that laŭflue and kontraŭflue are suitable translations. My question is mostly about relative positions. I can not find any word for expressing the fact of being up or down relatively to a stream.
Beside, "downstream" and "upstream" are often used in a metaphorical way. In molecular biology, a signal can be said to act "downstream" to the activation a receptor, and the receptor activation is said "upstream" of this signal. Both words are also used in software development. In these cases, is it better to keep the river metaphor, or to be more explicit?
Here are example sentences with my proposed translations:
- His house is downstream from mine. (Lia domo staras sub la mia laŭ la rivero.)
- The activation of the receptor causes the transmission of a downstream signal. (Aktivigo de la ricevilo estigas transmision/transdonon de laŭflua signalo.)
- Send a patch to upstream developer. (Sendu flikaĵon al kontraŭflua programisto.)
I am not not satisfied with the way I expressed relative positions. Laŭflua and kontraŭflua seem to refer to movements, not positions.